Archive for the ‘System Administration’ Category

Must have software on freshly installed windows – Essential Software after fresh Windows install

Friday, March 18th, 2016

Install-update-multiple-programs-applications-at-once-using-ninite

If you're into IT industry even if you don't like installing frequently Windows or you're completely Linux / BSD user, you will certainly have a lot of friends which will want help from you to re-install or fix their Windows 7 / 8 / 10 OS. At least this is the case with me every year, I'm kinda of obliged to install fresh windowses on new bought friends or relatives notebooks / desktop PCs.

Of course according to for whom the new Windows OS installed the preferrences of necessery software varies, however more or less there is sort of standard list of Windows Software which is used daily by most of Avarage Computer user, such as:
 

Not to forget a good candidate from the list to install on new fresh windows Installation candidates are:

  • Winrar
  • PeaZIP
  • WinZip
  • GreenShot (to be able to easily screenshot stuff and save pictures locally and to the cloud)
  • AnyDesk (non free but very functional alternative to TeamViewer) to be able to remotely access remote PC
  • TightVNC
  • ITunes / Spotify (for people who have also iPhone smart phone)
  • DropBox or pCloud (to have some extra cloud free space)
  • FBReader (for those reading a lot of books in different formats)
  • Rufus – Rufus is an efficient and lightweight tool to create bootable USB drives. It helps you to create BIOS or UEFI bootable devices. It helps you to create Windows TO Go drives. It provides support for various disk, format, and partition.
  • Recuva is a data recovery software for Windows 10 (non free)
  • EaseUS (for specific backup / restore data purposes but unfortunately (non free)
  • For designers
  • Adobe Photoshop
  • Adobe Illustrator
  • f.lux –  to control brightness of screen and potentially Save your eyes
  • ImDisk virtual Disk Driver
  • KeePass / PasswordSafe – to Securely store your passwords
  • Putty / MobaXterm / SecureCRT / mPutty (for system administrators and programmers that has to deal with Linux / UNIX)

I tend to install on New Windows installs and thus I have more or less systematized the process.

I try to usually stick to free software where possible for each of the above categories as a Free Software enthusiast and luckily nowadays there is a lot of non-priprietary or at least free as in beer software available out there.

For Windows sysadmins or College and other public institutions networks including multiple of Windows Computers which are not inside a domain and also for people in computer repair shops where daily dozens of windows pre-installs or a set of software Automatic updates are  necessery make sure to take a look at Ninite

ninite-automate-windows-program-deploy-and-update-on-new-windows-os-openoffice-screenshot

As official website introduces Ninite:

Ninite – Install and Update All Your Programs at Once

Of course as Ninite is used by organizations as NASA, Harvard Medical School etc. it is likely the tool might reports your installed list of Windows software and various other Win PC statistical data to Ninite developers and most likely NSA, but this probably doesn't much matter as this is probably by the moment you choose to have installed a Windows OS on your PC.

ninite-choises-to-build-an-install-package-with-useful-essential-windows-software-screenshot
 

For Windows System Administrators managing small and middle sized network PCs that are not inside a Domain Controller, Ninite could definitely save hours and at cases even days of boring install and maintainance work. HP Enterprise or HP Inc. Employees or ex-employees would definitely love Ninite, because what Ninite does is pretty much like the well known HP Internal Tool PC COE.

Ninite could also prepare an installer containing multiple applications based on the choice on Ninite's website, so that's also a great thing especially if you need to deploy a different type of Users PCs (Scientific / Gamers / Working etc.)

Perhaps there are also other useful things to install on a new fresh Windows installations, if you're using something I'm missing let me know in comments.

Create Bootable Windows installer USB from a MAC PC, MacBook host or Linux Desktop computer

Thursday, February 8th, 2024

Creating Windows bootable installer with Windows Media Creation tool is easy, but sometimes if you're a geek like me you don't have a Windows personal PC at home and your Work PC is so paranoidly restricted by its administrator through paranoid Domain Controller Policies, that you can only copy from a USB drive towards the Win PC but you cannot write to the USB. 

1. Preparing Linux installer USB via Mac's Boot Camp Assistant

If you're lucky you might have a MAC Book Air or some kind of other mac PC, if that is the case you can burn the Windows Installer iso, with the Native Mac tool called BootCamp Assistant, by simply downloading the Win Boot ISO, launching the app and burning it:

Finder > Applications > Utilities and open Boot Camp Assistant.

create-windows-10-bootable-installer-usb-mac-screenshot.png

2. Preparing Bootable Windows installer on Linux host machine

On DEBIAN / UBUNTU and other Deb based Linuxes

# apt install gddrescue 

On CENTOS / FEDORA :

# dnf install ddrescue

To install the Windows Image to the right USB drive, first find it out with fdisk and list it:

# fdisk -l
 

Disk /dev/sdb: 14.41 GiB, 15472047104 bytes, 30218842 sectors
Disk model: DataTraveler 3.0
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xc23dc587

Device     Boot    Start      End  Sectors  Size Id Type
/dev/sdb1           8192 30216793 30208602 14.4G  7 HPFS/NTFS/exFAT
/dev/sdb2       30216794 30218841     2048    1M  e W95 FAT16 (LBA)

Then Use ddrescue to create the bootable MS windows Installer USB disk.

# ddrescue windows10.iso /dev/sd1 –force -D

3. Using GUI Linux tool WoeUSB-ng to prepare Microsoft Windows start up USB drive

If you're a lazy Linux user and you plan to prepare up to date Windows image files regularly, perhaps the WoeUSB-ng Graphical tool will suit you better, to use it you will have to install a bunch of python libraries.
 

On Ubuntu Linux:

# apt install git p7zip-full python3-pip python3-wxgtk4.0 grub2-common grub-pc-bin
# pip3 install WoeUSB-ng

On Fedora Linux:

dnf install git p7zip p7zip-plugins python3-pip python3-wxpython4
# sudo pip3 install WoeUSB-ng

Launch the WoeUSB-ng program :

 

$ python3 /usr/local/bin/woeusbgui

 

Download, the latest Version of Windows Installer .ISO IMAGE file, plug in your USB flash disk and let the program burn the ISO and create the GRUB boot loader, that will make WIndows installer bootable on your PC.

WoeUSB-ng-python-burn-windows-installer.-tool-screenshot

With WoeUSB-ng you have to be patient, it will take some time to prepare and copy the Windows installer content and will take about 15 to 20 minutes from my experience to finalize the GRUB records required, that will make the new burnt ISO bootable.


Then just plug it in to your Desktop PC or laptop, virtual machine, whatever where you would like to install the Windows from its latest installation Source image and Go on with doing the necessery evil to have Microsoft Spy on you permanently.

P.S. I just learned, from colleagues from Kvant Serviz (a famous hardware second hand, shop and repair shop here in Bulgaria, that nowadays Windows has evolved to the points, they can and they actually do overwrite the PC BIOS / UEFI as part of updates without any asking the end user !!!
At first I disbelived that, but after a short investigation online it turned out this is true, 
there are discussions online from people complaining, that WIndows updates has ovewritten their current BIOS settings and people complaining BIOS versions are ovewritten.

Enjoy your new personal Spy OS ! 🙂

Zabbix script to track arp address cache loss (arp incomplete) from Linux server to gateway IP

Tuesday, January 30th, 2024

Zabbix_arp-network-incomplete-check-logo.svg

Some of the Linux servers recently, I'm responsible had a very annoying issue recently. The problem is ARP address to default configured server gateway is being lost, every now and then and it takes up time, fot the remote CISCO router to realize the problem and resolve it. We have debugged with the Network expert colleague, while he was checking the Cisco router and we were checking the arp table on the Linux server with arp command. And we came to conclusion this behavior is due to some network mess because of too many NAT address configurations on the network or due to a Cisco bug. The colleagues asked Cisco but cisco does not have any solution to the issue and the only close work around for the gateway loosing the mac is to set a network rule on the Cisco router to flush its arp record for the server it was loosing the MAC address for.
This does not really solve completely the problem but at least, once we run into the issue, it gets resolved as quick as 5 minutes time. }

As we run a cluster environment it is useful to Monitor and know immediately once we hit into the MAC gateway disappear issue and if the issue persists, exclude the Linux node from the Cluster so we don't loose connection traffic.
For the purpose of Monitoring MAC state from the Linux haproxy machine towards the Network router GW, I have developed a small userparameter script, that is periodically checking the state of the MAC address of the IP address of remote gateway host and log to a external file for any problems with incomplete MAC address of the Remote configured default router.

In case if you happen to need the same MAC address state monitoring for your servers, I though that might be of a help to anyone out there.
To monitor MAC address incomplete state with Zabbix, do the following:
 

1. Create  userparamater_arp_gw_check.conf Zabbix script
 

# cat userparameter_arp_gw_check.conf 
UserParameter=arp.check,/usr/local/bin/check_gw_arp.sh

 

2. Create the following shell script /usr/local/bin/check_gw_arp.sh

 

#!/bin/bash
# simple script to run on cron peridically or via zabbix userparameter
# to track arp loss issues to gateway IP
#gw_ip='192.168.0.55';
gw_ip=$(ip route show|grep -i default|awk '{ print $3 }');
log_f='/var/log/arp_incomplete.log';
grep_word='incomplete';
inactive_status=$(arp -n "$gw_ip" |grep -i $grep_word);
# if GW incomplete record empty all is ok
if [[ $inactive_status == ” ]]; then 
echo $gw_ip OK 1; 
else 
# log inactive MAC to gw_ip
echo "$(date '+%Y-%m-%d %H:%M:%S')" "ARP_ERROR $inactive_status 0" | tee -a $log_f 2>&1 >/dev/null;
# printout to zabbix
echo "1 ARP FAILED: $inactive_status"; 
fi

You can download the check_gw_arp.sh here.

The script is supposed to automatically grep for the Default Gateway router IP, however before setting it up. Run it and make sure this corresponds correctly to the default Gateway IP MAC you would like to monitor.
 

3. Create New Zabbix Template for ARP incomplete monitoring
 

arp-machine-to-default-gateway-failure-monitoring-template-screenshot

Create Application 

*Name
Default Gateway ARP state

4. Create Item and Dependent Item 
 

Create Zabbix Item and Dependent Item like this

arp-machine-to-default-gateway-failure-monitoring-item-screenshot

 

arp-machine-to-default-gateway-failure-monitoring-item1-screenshot

arp-machine-to-default-gateway-failure-monitoring-item2-screenshot


5. Create Trigger to trigger WARNING or whatever you like
 

arp-machine-to-default-gateway-failure-monitoring-trigger-screenshot


arp-machine-to-default-gateway-failure-monitoring-trigger1-screenshot

arp-machine-to-default-gateway-failure-monitoring-trigger2-screenshot


6. Create Zabbix Action to notify via Email etc.
 

arp-machine-to-default-gateway-failure-monitoring-action1-screenshot

 

arp-machine-to-default-gateway-failure-monitoring-action2-screenshot

That's all. Once you set up this few little things, you can enjoy having monitoring Alerts for your ARP state incomplete on your Linux / Unix servers.
Enjoy !

KVM Creating LIVE and offline VM snapshot backup of Virtual Machines. Restore KVM VM from backup. Delete old KVM backups

Tuesday, January 16th, 2024

kvm-backup-restore-vm-logo

For those who have to manage Kernel-Based Virtual Machines it is a must to create periodic backups of VMs. The backup is usually created as a procedure part of the Update plan (schedule) of the server either after shut down the machine completely or live.

Since KVM is open source the very logical question for starters, whether KVM supports Live backups. The simple answer is Yes it does.

virsh command as most people know is the default command to manage VMs on KVM running Hypervisor servers to manage the guest domains.

KVM is flexible and could restore a VM based on its XML configuration and the VM data (either a static VM single file) or a filesystem laying on LVM filesystem etc.

To create a snapshot out of the KVM HV, list all VMs and create the backup:

# export VM-NAME=fedora;
# export SNAPSHOT-NAME=fedora-backup;
# virsh list –all


It is useful to check out the snapshot-create-as sub arguments

 

 

# virsh help snapshot-create-as

 OPTIONS
    [–domain] <string>  domain name, id or uuid
    –name <string>  name of snapshot
    –description <string>  description of snapshot
    –print-xml      print XML document rather than create
    –no-metadata    take snapshot but create no metadata
    –halt           halt domain after snapshot is created
    –disk-only      capture disk state but not vm state
    –reuse-external  reuse any existing external files
    –quiesce        quiesce guest's file systems
    –atomic         require atomic operation
    –live           take a live snapshot
    –memspec <string>  memory attributes: [file=]name[,snapshot=type]
    [–diskspec]  disk attributes: disk[,snapshot=type][,driver=type][,file=name]

 

# virsh shutdown $VM_NAME
# virsh snapshot-create-as –domain $VM-NAME –name "$SNAPSHOT-NAME"


1. Creating a KVM VM LIVE (running machine) backup
 

# virsh snapshot-create-as –domain debian \
–name "debian-snapshot-2024" \
–description "VM Snapshot before upgrading to latest Debian" \
–live

On successful execution of KVM Virtual Machine live backup, should get something like:

Domain snapshot debian-snapshot-2024 created

 

2. Listing backed-up snapshot content of KVM machine
 

# virsh snapshot-list –domain debian


a. To get more extended info about a previous snapshot backup

# virsh snapshot-info –domain debian –snapshotname debian-snapshot-2024


b. Listing info for multiple attached storage qcow partition to a VM
 

# virsh domblklist linux-guest-vm1 –details

Sample Output would be like:

 Type   Device   Target   Source
——————————————————————-
 file   disk     vda      /kvm/linux-host/linux-guest-vm1_root.qcow2
 file   disk     vdb      /kvm/linux-host/linux-guest-vm1_attached_storage.qcow2
 file   disk     vdc      /kvm/linux-host/guest01_logging_partition.qcow2
 file   cdrom    sda      –
 file   cdrom    sdb      

 

3. Backup KVM only Virtual Machine data files (but not VM state) Live

 

# virsh snapshot-create-as –name "mint-snapshot-2024" \
–description "Mint Linux snapshot" \
–disk-only \
–live
–domain mint-home-desktop


4. KVM restore snapshot (backup)
 

To revert backup VM state to older backup snapshot:
 

# virsh shutdown –domain manjaro
# virsh snapshot-revert –domain manjaro –snapshotname manjaro-linux-back-2024 –running


5. Delete old unnecessery KVM VM backup
 

# virsh snapshot-delete –domain dragonflybsd –snapshotname dragonfly-freebsd

 

Debugging routing and network issues on Linux common approaches. A step by step guide to find out why routing or network service fails

Thursday, November 30th, 2023

For system administrators having a Network issue is among the Hell-ish stuff that can happen every now and then. That is especially true in Heterogenous / Hybrid and complicated Network topologies (with missing well crafted documentation), that were build without an initial overview "on the fly".
Such a networking connectivity or routing issues are faced by every novice, mid or even expert system administrators as the Company's Network IT environments are becoming more and more complicated day by day.

When the "Disaster" of being unable to connect two servers or at times  home laptops / PCs to see each other even though on the Physical layer / Transport Layer (Hardware such as external Switches / Routers / Repeaters / Cabling etc.) is Present machines are connected and everything on the 1 Physical Layer from OSI layears is present happens, then it is time to Debug it with some software tools and methods.

To each operating system the tools and methods to test networking connection and routings is a bit different but generally speaking most concepts are pretty much the same across different types of operating systems (Linux ditros / OpenBSD / FreeBSD / Mac OS / Android / iOS / HP-UX / IBM AIX / DOS / Windows etc.).

Debugging network issues across separate operating systems has its variations but in this specific (ideas) are much close to this article. As the goal at that guide will be to point out how to debug network issues on Linux, in future if I have the time or need to debug other OS-es from Linux, I'll try to put an article on how to debug Network issues on Windows when have some time to do it.

Consider to look for the issue following the basic TCP / IP OSI Level model, every system administrator should have idea about it already, it is part of most basic networking courses such as Cisco's CCNA

TCPIP_OSI_model-networking-levels

1. Check what is the Link status of the Interface with ethtool
 

root@freak:~# ethtool eno1
Settings for eno1:
    Supported ports: [ TP ]
    Supported link modes:   10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
                            1000baseT/Full
    Supported pause frame use: Symmetric
    Supports auto-negotiation: Yes
    Supported FEC modes: Not reported
    Advertised link modes:  10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
                            1000baseT/Full
    Advertised pause frame use: Symmetric
    Advertised auto-negotiation: Yes
    Advertised FEC modes: Not reported
    Speed: 100Mb/s
    Duplex: Full
    Auto-negotiation: on
    Port: Twisted Pair
    PHYAD: 1
    Transceiver: internal
    MDI-X: on (auto)
    Supports Wake-on: pumbg
    Wake-on: g
        Current message level: 0x00000007 (7)
                               drv probe link
    Link detected: yes

 

root@freak:~# ethtool eno2
Settings for eno2:
    Supported ports: [ TP ]
    Supported link modes:   10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
                            1000baseT/Full
    Supported pause frame use: Symmetric
    Supports auto-negotiation: Yes
    Supported FEC modes: Not reported
    Advertised link modes:  10baseT/Half 10baseT/Full
                            100baseT/Half 100baseT/Full
                            1000baseT/Full
    Advertised pause frame use: Symmetric
    Advertised auto-negotiation: Yes
    Advertised FEC modes: Not reported
    Speed: 1000Mb/s
    Duplex: Full
    Auto-negotiation: on
    Port: Twisted Pair
    PHYAD: 1
    Transceiver: internal
    MDI-X: on (auto)
    Supports Wake-on: pumbg
    Wake-on: g
        Current message level: 0x00000007 (7)
                               drv probe link
    Link detected: yes

 

For example lets check only if Cable of Network card is plugged in and detected to have a network connection to remote node or switch and show the connection speed on which the 'autoneg on' (autonegiation option) of the LAN card has detected the network exat maximum speed:

root@pcfreak:~# ethtool eth0|grep -i 'link detected'; ethtool eth0 |grep 'Speed: '
    Link detected: yes
    Speed: 100Mb/s


1. Check ip command network configuration output

root@freak:~# ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr0 state UP group default qlen 1000
    link/ether 70:e2:84:13:44:15 brd ff:ff:ff:ff:ff:ff
    altname enp7s0
3: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr1 state UP group default qlen 1000
    link/ether 70:e2:84:13:44:17 brd ff:ff:ff:ff:ff:ff
    altname enp8s0
4: xenbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 70:e2:84:13:44:13 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.7/24 brd 192.168.1.255 scope global dynamic xenbr0
       valid_lft 7361188sec preferred_lft 7361188sec
5: xenbr1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 70:e2:84:13:44:15 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.5/24 brd 192.168.0.255 scope global dynamic xenbr1
       valid_lft 536138sec preferred_lft 536138sec
10: vif2.0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr0 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
11: vif2.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr1 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
12: vif3.0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr0 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
13: vif3.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr1 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
14: vif4.0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr0 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
15: vif4.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr1 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
16: vif5.0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr0 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
17: vif5.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr1 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
18: vif6.0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr0 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
19: vif6.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr0 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
30: vif17.0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr0 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
31: vif17.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr1 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
34: vif21.0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr0 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
35: vif21.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master xenbr1 state UP group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
48: vif25.0-emu: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master xenbr0 state UNKNOWN group default qlen 1000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
49: vif25.1-emu: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master xenbr1 state UNKNOWN group default qlen 1000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
50: vif25.0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq master xenbr0 state DOWN group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
51: vif25.1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq master xenbr1 state DOWN group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
118: vif47.0-emu: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master xenbr0 state UNKNOWN group default qlen 1000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
119: vif47.1-emu: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master xenbr1 state UNKNOWN group default qlen 1000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
120: vif47.0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq master xenbr0 state DOWN group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
121: vif47.1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq master xenbr1 state DOWN group default qlen 2000
    link/ether fe:ff:ff:ff:ff:ff brd ff:ff:ff:ff:ff:ff
root@freak:~# 

ip a s (is a also a shortcut command alias) you can enjoy if you have to deal with ip command frequently.

2. Check the status of the interfaces

Old fashioned way is to just do:

/sbin/ifconfig

 

root@freak:~# ifconfig 
eno1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether 70:e2:84:13:44:15  txqueuelen 1000  (Ethernet)
        RX packets 52366502  bytes 10622469320 (9.8 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 242622195  bytes 274688121244 (255.8 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0xfb200000-fb27ffff  

eno2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether 70:e2:84:13:44:17  txqueuelen 1000  (Ethernet)
        RX packets 220995454  bytes 269698276095 (251.1 GiB)
        RX errors 0  dropped 7  overruns 0  frame 0
        TX packets 192319925  bytes 166233773782 (154.8 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0xfb100000-fb17ffff  

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 2553  bytes 147410 (143.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2553  bytes 147410 (143.9 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif17.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 14517375  bytes 133226551792 (124.0 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 139688950  bytes 145111993017 (135.1 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif17.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 86113294  bytes 156944058681 (146.1 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 181513904  bytes 267892940821 (249.4 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif2.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 1521875  bytes 88282472 (84.1 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 152691174  bytes 278372314505 (259.2 GiB)
        TX errors 0  dropped 3 overruns 0  carrier 0  collisions 0

vif2.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 454915  bytes 81069760 (77.3 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 266953989  bytes 425692364876 (396.4 GiB)
        TX errors 0  dropped 26 overruns 0  carrier 0  collisions 0

vif21.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 20043711  bytes 1283926794 (1.1 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 141580485  bytes 277396881113 (258.3 GiB)
        TX errors 0  dropped 3 overruns 0  carrier 0  collisions 0

vif21.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 73004  bytes 3802174 (3.6 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 267151006  bytes 425621892663 (396.3 GiB)
        TX errors 0  dropped 14 overruns 0  carrier 0  collisions 0

vif25.0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif25.1: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif25.0-emu: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 1000  (Ethernet)
        RX packets 2736348  bytes 295661367 (281.9 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 260385509  bytes 265751226663 (247.5 GiB)
        TX errors 0  dropped 200 overruns 0  carrier 0  collisions 0

vif25.1-emu: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 1000  (Ethernet)
        RX packets 145387  bytes 36011655 (34.3 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 370314760  bytes 394725961081 (367.6 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif3.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 55382861  bytes 130042280927 (121.1 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 99040097  bytes 147929196318 (137.7 GiB)
        TX errors 0  dropped 1 overruns 0  carrier 0  collisions 0

vif3.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 5132631  bytes 295493762 (281.8 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 262314199  bytes 425416945203 (396.2 GiB)
        TX errors 0  dropped 16 overruns 0  carrier 0  collisions 0

vif4.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 4902015  bytes 615387539 (586.8 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 149342891  bytes 277802504143 (258.7 GiB)
        TX errors 0  dropped 1 overruns 0  carrier 0  collisions 0

vif4.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 276927  bytes 30720101 (29.2 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 267132395  bytes 425745668273 (396.5 GiB)
        TX errors 0  dropped 14 overruns 0  carrier 0  collisions 0

vif47.0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif47.1: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif47.0-emu: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 1000  (Ethernet)
        RX packets 208745  bytes 20096596 (19.1 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 110905731  bytes 110723486135 (103.1 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif47.1-emu: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 1000  (Ethernet)
        RX packets 140517  bytes 14596061 (13.9 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 150831959  bytes 162931572456 (151.7 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif5.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 2030528  bytes 363988589 (347.1 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 152264264  bytes 278131541781 (259.0 GiB)
        TX errors 0  dropped 1 overruns 0  carrier 0  collisions 0

vif5.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 4169244  bytes 1045889687 (997.4 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 263561100  bytes 424894400987 (395.7 GiB)
        TX errors 0  dropped 7 overruns 0  carrier 0  collisions 0

vif6.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 300242  bytes 16210963 (15.4 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 153909576  bytes 278461295620 (259.3 GiB)
        TX errors 0  dropped 2 overruns 0  carrier 0  collisions 0

vif6.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 43  bytes 1932 (1.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 154205631  bytes 278481298141 (259.3 GiB)
        TX errors 0  dropped 2 overruns 0  carrier 0  collisions 0

xenbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.8  netmask 255.255.255.0  broadcast 192.168.1.255
        ether 70:e2:84:13:44:11  txqueuelen 1000  (Ethernet)
        RX packets 13689902  bytes 923464162 (880.6 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12072932  bytes 1307055530 (1.2 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

xenbr1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.0.3  netmask 255.255.255.0  broadcast 192.168.0.255
        ether 70:e2:84:13:44:12  txqueuelen 1000  (Ethernet)
        RX packets 626995  bytes 180026901 (171.6 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12815  bytes 942092 (920.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

 

root@freak:~# ifconfig        
eno1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether 70:e2:84:13:44:11  txqueuelen 1000  (Ethernet)
        RX packets 52373358  bytes 10623034427 (9.8 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 242660000  bytes 274734018669 (255.8 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0xfb200000-fb27ffff  

eno2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether 70:e2:84:13:44:12  txqueuelen 1000  (Ethernet)
        RX packets 221197892  bytes 269978137472 (251.4 GiB)
        RX errors 0  dropped 7  overruns 0  frame 0
        TX packets 192573206  bytes 166491370299 (155.0 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device memory 0xfb100000-fb17ffff  

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 2553  bytes 147410 (143.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2553  bytes 147410 (143.9 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif17.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 14519247  bytes 133248290251 (124.0 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 139708738  bytes 145135168676 (135.1 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif17.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 86206104  bytes 157189755115 (146.3 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 181685983  bytes 268170806613 (249.7 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif2.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 1522072  bytes 88293701 (84.2 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 152712638  bytes 278417240910 (259.2 GiB)
        TX errors 0  dropped 3 overruns 0  carrier 0  collisions 0

vif2.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 454933  bytes 81071616 (77.3 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 267218860  bytes 426217224334 (396.9 GiB)
        TX errors 0  dropped 26 overruns 0  carrier 0  collisions 0

vif21.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 20045530  bytes 1284038375 (1.1 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 141601066  bytes 277441739746 (258.3 GiB)
        TX errors 0  dropped 3 overruns 0  carrier 0  collisions 0

vif21.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 73010  bytes 3802474 (3.6 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 267415889  bytes 426146753845 (396.8 GiB)
        TX errors 0  dropped 14 overruns 0  carrier 0  collisions 0

vif25.0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif25.1: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif25.0-emu: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 1000  (Ethernet)
        RX packets 2736576  bytes 295678097 (281.9 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 260429831  bytes 265797660906 (247.5 GiB)
        TX errors 0  dropped 200 overruns 0  carrier 0  collisions 0

vif25.1-emu: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 1000  (Ethernet)
        RX packets 145425  bytes 36018716 (34.3 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 370770440  bytes 395263409640 (368.1 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif3.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 55392503  bytes 130064444520 (121.1 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 99052116  bytes 147951838129 (137.7 GiB)
        TX errors 0  dropped 1 overruns 0  carrier 0  collisions 0

vif3.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 5133054  bytes 295517366 (281.8 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 262578665  bytes 425941777243 (396.6 GiB)
        TX errors 0  dropped 16 overruns 0  carrier 0  collisions 0

vif4.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 4902949  bytes 615496460 (586.9 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 149363618  bytes 277847322538 (258.7 GiB)
        TX errors 0  dropped 1 overruns 0  carrier 0  collisions 0

vif4.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 276943  bytes 30721141 (29.2 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 267397268  bytes 426270528575 (396.9 GiB)
        TX errors 0  dropped 14 overruns 0  carrier 0  collisions 0

vif47.0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif47.1: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif47.0-emu: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 1000  (Ethernet)
        RX packets 208790  bytes 20100733 (19.1 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 110950236  bytes 110769932971 (103.1 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif47.1-emu: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 1000  (Ethernet)
        RX packets 140551  bytes 14599509 (13.9 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 151287643  bytes 163469024604 (152.2 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

vif5.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 2030676  bytes 363997181 (347.1 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 152285777  bytes 278176471509 (259.0 GiB)
        TX errors 0  dropped 1 overruns 0  carrier 0  collisions 0

vif5.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 4169387  bytes 1045898303 (997.4 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 263825846  bytes 425419251935 (396.2 GiB)
        TX errors 0  dropped 7 overruns 0  carrier 0  collisions 0

vif6.0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 300266  bytes 16212271 (15.4 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 153931212  bytes 278506234302 (259.3 GiB)
        TX errors 0  dropped 2 overruns 0  carrier 0  collisions 0

vif6.1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether fe:ff:ff:ff:ff:ff  txqueuelen 2000  (Ethernet)
        RX packets 43  bytes 1932 (1.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 154227291  bytes 278526238467 (259.3 GiB)
        TX errors 0  dropped 2 overruns 0  carrier 0  collisions 0

xenbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.8  netmask 255.255.255.0  broadcast 192.168.1.255
        ether 70:e2:84:13:44:11  txqueuelen 1000  (Ethernet)
        RX packets 13690768  bytes 923520126 (880.7 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12073667  bytes 1307127765 (1.2 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

xenbr1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.0.3  netmask 255.255.255.0  broadcast 192.168.0.255
        ether 70:e2:84:13:44:12  txqueuelen 1000  (Ethernet)
        RX packets 627010  bytes 180028847 (171.6 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12815  bytes 942092 (920.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

 

To see ethernet interfaces that seem up and then do a ifconfig -a to check whether some interfaces are down (e.g. not shown in the simple ifconfig list).
/sbin/ifconfig -a

! Please note that some virtual IP configurations might not appear and noly be visible in an (ip addr show) command.

 

3. Check iproute2 for special rt_tables (Routing Tables) rules
 

By default Linux distributions does not have any additional rules in /etc/iproute2/rt_tables however some Linux router machines, needs to have a multiple Gateways. Perhaps the most elegant way to do multiple routings with Linux is to use iproute2's routing tables rt_tables.

Here is example of an OpenXEN system that has 2 Internet providers attached and routes different traffic via

 

root@freak:~# cat /etc/iproute2/rt_tables
#
# reserved values
#
255    local
254    main
253    default

100    INET1
200     INET2
0    unspec
#
# local
#
#1    inr.ruhep

 

root@freak:~# ip rule list
0:    from all lookup local
32762:    from all to 192.168.1.8 lookup INET2
32763:    from 192.168.1.8 lookup INET2
32764:    from all to 192.168.0.3 lookup INET1
32765:    from 192.168.0.3 lookup INET1
32766:    from all lookup main
32767:    from all lookup default
root@freak:~# 
 

4. Using ip route get to find out traffic route (path)

root@freak:~# ip route get 192.168.0.1
192.168.0.1 via 192.168.0.1 dev xenbr1 src 192.168.0.3 uid 0 
    cache 

 

root@freak:~# /sbin/route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 xenbr0
192.168.0.0     192.168.0.1     255.255.255.0   UG    0      0        0 xenbr1
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 xenbr1
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 xenbr0
root@freak:~# 

root@freak:~# ip route show
default via 192.168.1.1 dev xenbr0 
192.168.0.0/24 via 192.168.0.1 dev xenbr1 
192.168.0.0/24 dev xenbr1 proto kernel scope link src 192.168.0.3 
192.168.1.0/24 dev xenbr0 proto kernel scope link src 192.168.1.8 


If you find that gateway is missing you might want to add it with:

root@freak:~#  ip route add default via 192.168.5.1

If you need to add a speicic network IP range via separate gateways, you can use commands like:

To add routing for 192.168.0.1/24 / 192.168.1.1/24 via 192.168.0.1 and 192.168.1.1

# /sbin/route add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.1.1 dev eth1
# /sbin/route add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.0.1 dev eth1

 

If you need to delete a configured wrong route with ip command

# ip route del 192.168.1.0/24 via 0.0.0.0 dev eth1
# ip route del 192.168.0.0/24 via 0.0.0.0 dev eth1

5. Use ping (ICMP protocol) the Destionation IP
 

root@freak:~# ping -c 3 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_seq=1 ttl=64 time=0.219 ms
64 bytes from 192.168.0.1: icmp_seq=2 ttl=64 time=0.295 ms
64 bytes from 192.168.0.1: icmp_seq=3 ttl=64 time=0.270 ms

— 192.168.0.1 ping statistics —
3 packets transmitted, 3 received, 0% packet loss, time 2048ms
rtt min/avg/max/mdev = 0.219/0.261/0.295/0.031 ms
root@freak:~# ping -c 3 192.168.0.39
PING 192.168.0.39 (192.168.0.39) 56(84) bytes of data.
From 192.168.1.80: icmp_seq=2 Redirect Host(New nexthop: 192.168.0.39)
From 192.168.1.80: icmp_seq=3 Redirect Host(New nexthop: 192.168.0.39)
From 192.168.1.80 icmp_seq=1 Destination Host Unreachable


— 192.168.0.39 ping statistics —
3 packets transmitted, 0 received, +1 errors, 100% packet loss, time 2039ms
pipe 3

 

Note that sometimes you might get 100% traffic loss but still have connection to the destionation in case if the ICMP protocol is filtered for security.

However if you get something like Network is unreachable that is usually an indicator of some routing problem or wrongly configured network netmask.

root@freak:~# ping 192.168.0.5
ping: connect: Network is unreachable

Test network with different packet size. To send 8972 bytes of payload in a Ethernet frame without fragmentation, the following command can be used:

root@pcfreak:~# ping -s 8972 -M do -c 4 freak
PING xen (192.168.1.8) 8972(9000) bytes of data.
ping: local error: message too long, mtu=1500
ping: local error: message too long, mtu=1500
ping: local error: message too long, mtu=1500
^C
— xen ping statistics —
3 packets transmitted, 0 received, +3 errors, 100% packet loss, time 2037ms

root@pcfreak:~# 


 -M pmtudisc_opt
           Select Path MTU Discovery strategy.  pmtudisc_option may be either do (prohibit fragmentation, even local one), want (do PMTU discovery, fragment locally when packet size is
           large), or dont (do not set DF flag).

 

root@pcfreak:~# ping -s 8972 -M want -c 4 freak
PING xen (192.168.1.8) 8972(9000) bytes of data.
8980 bytes from xen (192.168.1.5): icmp_seq=1 ttl=64 time=2.18 ms
8980 bytes from xen (192.168.1.5): icmp_seq=2 ttl=64 time=1.90 ms
8980 bytes from xen (192.168.1.5): icmp_seq=3 ttl=64 time=2.10 ms
^C
— xen ping statistics —
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 1.901/2.059/2.178/0.116 ms

root@pcfreak:~# 

  • -M do: prohibit fragmentation
  • -s 8972 8972 bytes of data
  • ICMP header: 8 bytes
  • IP header: 20 bytes (usually, it can be higher)
  • 8980 bytes of bytes is the IP payload
     

These commands can be used to capture for MTU (maximum transmition units) related issues between hosts that are preventing for hosts to properly send traffic between themselves.
A common issue for Linux hosts to be unable to see each other on the same network is caused by Jumbo Frames (MTU 9000) packets enabled on one of the sides and MTU of 1500 on the other side.
Thus it is always a good idea to thoroughully look up all configured MTUs for all LAN Devices on each server.

6. Check traceroute path to host

If there is no PING but ip route get shows routing is properly configured and the routes existing in the Linux machine routing tables, next step is to check the output of traceroute / tracepath / mtr

 

raceroute to 192.168.0.1 (192.168.0.1), 30 hops max, 60 byte packets
 1  pcfreak (192.168.0.1)  0.263 ms  0.166 ms  0.119 ms
root@freak:~# tracepath 192.168.1.1
 1?: [LOCALHOST]                      pmtu 1500
 1:  vivacom-gigabit-router                                0.925ms reached
 1:  vivacom-gigabit-router                                0.835ms reached
     Resume: pmtu 1500 hops 1 back 1 

 

It might be useful to get a frequent output of the command (especially on Linux hosts) where mtr command is not installed with:

 

root@freak:~# watch -n 0.1 traceroute 192.168.0.1

 

root@freak:~# traceroute -4 google.com
traceroute to google.com (172.217.17.110), 30 hops max, 60 byte packets
 1  vivacom-gigabit-router (192.168.1.1)  0.657 ms  1.280 ms  1.647 ms
 2  213.91.190.130 (213.91.190.130)  7.983 ms  8.168 ms  8.097 ms
 3  * * *
 4  * * *
 5  212-39-66-222.ip.btc-net.bg (212.39.66.222)  16.613 ms  16.336 ms  17.151 ms
 6  * * *
 7  142.251.92.65 (142.251.92.65)  18.808 ms  13.246 ms 209.85.254.242 (209.85.254.242)  15.541 ms
 8  142.251.92.3 (142.251.92.3)  14.223 ms 142.251.227.251 (142.251.227.251)  14.507 ms 142.251.92.3 (142.251.92.3)  15.328 ms
 9  ams15s29-in-f14.1e100.net (172.217.17.110)  14.097 ms  14.909 ms 142.251.242.230 (142.251.242.230)  13.481 ms
root@freak:~# 

If you have MTR then you can get plenty of useful additional information such as the Network HOP name or the Country location of the HOP.

 

To get HOP name:

 

root@freak:~# mtr -z google.com

 

To get info on where (which Country) exactly network HOP is located physically:

root@freak:~# mtr -y 2 google.com

 

7. Check iptables INPUT / FORWARD / OUTPUT rules are messing with something
 

# iptables -L -n 

# iptables -t nat -L -n


Ideally you would not have any firewall

# iptables -L -n 

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         

# iptables -t nat -L -n
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination         

Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination         
 


In case if something like firewalld is enabled as a default serviceto provide some modern Linux firewall as Ubuntu and Redhat / CentOS / Fedoras has it often turned on as a service stop and disable the service

# systemctl stop firewalld

# systemctl disable firewalld

 

8. Debug for any possible MAC address duplicates
 

root@pcfrxen:~# arp -an
? (192.168.1.33) at 00:16:3e:59:96:9e [ether] on eth0
? (192.168.1.1) at 18:45:93:c6:d8:00 [ether] on eth1
? (192.168.0.1) at 8c:89:a5:f2:e8:d9 [ether] on eth1
? (192.168.1.1) at 18:45:93:c6:d8:00 [ether] on eth0
? (192.168.1.11) at 7c:0a:3f:89:b6:fa [ether] on eth1
? (192.168.1.17) at <incomplete> on eth0
? (192.168.1.37) at 00:16:3e:ea:05:ce [ether] on eth0
? (192.168.1.80) at 8c:89:a5:f2:e7:d8 [ether] on eth0
? (192.168.1.11) at 7c:0a:3f:89:a5:fa [ether] on eth0
? (192.168.1.30) at 00:16:3e:bb:46:45 [ether] on eth1
? (192.168.0.210) at 00:16:3e:68:d9:55 [ether] on eth1
? (192.168.1.30) at 00:16:3e:bb:46:45 [ether] on eth0
? (192.168.1.18) at 00:16:3e:0d:40:05 [ether] on eth1
? (192.168.0.211) at 00:16:3e:4d:41:05 [ether] on eth1
? (192.168.1.35) at 00:16:3e:d1:8f:77 [ether] on eth0
? (192.168.1.18) at 00:16:3e:0d:43:05 [ether] on eth0
? (192.168.1.28) at 00:16:3e:04:12:1c [ether] on eth1
? (192.168.0.3) at 70:e2:84:13:43:12 [ether] on eth1
? (192.168.0.208) at 00:16:3e:51:de:9c [ether] on eth1
? (192.168.0.241) at 00:16:3e:0d:48:06 [ether] on eth1
? (192.168.1.28) at 00:16:3e:04:12:1c [ether] on eth0
? (192.168.1.33) at 00:16:3e:59:97:8e [ether] on eth1
? (192.168.0.241) at 00:16:3e:0d:45:06 [ether] on eth0
? (192.168.0.209) at 00:16:3e:5c:df:96 [ether] on eth1

root@pcfrxen:~# ip neigh show
192.168.1.33 dev eth0 lladdr 00:16:3e:59:96:9e REACHABLE
192.168.1.1 dev eth1 lladdr 18:45:93:c6:d8:00 STALE
192.168.0.1 dev eth1 lladdr 8c:89:a5:f2:e8:d9 REACHABLE
192.168.1.1 dev eth0 lladdr 18:45:93:c6:d9:01 REACHABLE
192.168.1.11 dev eth1 lladdr 7c:0a:3f:89:a6:fb STALE
192.168.1.17 dev eth0  FAILED
192.168.1.37 dev eth0 lladdr 00:16:3e:ea:06:ce STALE
192.168.1.80 dev eth0 lladdr 8c:89:a5:f2:e8:d9 REACHABLE
192.168.1.11 dev eth0 lladdr 7c:0a:3f:89:a7:fa STALE
192.168.1.30 dev eth1 lladdr 00:16:3e:bb:45:46 STALE
192.168.0.210 dev eth1 lladdr 00:16:3e:68:d8:56 REACHABLE
192.168.1.30 dev eth0 lladdr 00:16:3e:bb:45:46 STALE
192.168.1.18 dev eth1 lladdr 00:16:3e:0d:48:04 STALE
192.168.0.211 dev eth1 lladdr 00:16:3e:4d:40:04 STALE
192.168.1.35 dev eth0 lladdr 00:16:3e:d2:8f:76 STALE
192.168.1.18 dev eth0 lladdr 00:16:3e:0d:48:06 STALE
192.168.1.28 dev eth1 lladdr 00:16:3e:04:11:2c STALE
192.168.0.3 dev eth1 lladdr 70:e2:84:13:44:13 STALE
192.168.0.208 dev eth1 lladdr 00:16:3e:51:de:9c REACHABLE
192.168.0.241 dev eth1 lladdr 00:16:3e:0d:48:07 STALE
192.168.1.28 dev eth0 lladdr 00:16:3e:04:12:1c REACHABLE
192.168.1.33 dev eth1 lladdr 00:16:3e:59:96:9e STALE
192.168.0.241 dev eth0 lladdr 00:16:3e:0d:49:06 STALE
192.168.0.209 dev eth1 lladdr 00:16:3e:5c:dd:97 STALE
root@pcfrxen:~# 


9. Check out with netstat / ss for any irregularities such as high amount of error of faulty ICMP / TCP / UDP network packs

 

For example check out the netstat network stack output

# netstat -s

 

root@pcfrxen:~# netstat -s
Ip:
    Forwarding: 2
    440044929 total packets received
    1032 with invalid addresses
    0 forwarded
    0 incoming packets discarded
    439988902 incoming packets delivered
    396161852 requests sent out
    3 outgoing packets dropped
    100 dropped because of missing route
Icmp:
    1025 ICMP messages received
    540 input ICMP message failed
    ICMP input histogram:
        destination unreachable: 1014
        timeout in transit: 11
    519 ICMP messages sent
    0 ICMP messages failed
    ICMP output histogram:
        destination unreachable: 519
IcmpMsg:
        InType3: 1014
        InType11: 11
        OutType3: 519
Tcp:
    1077237 active connection openings
    1070510 passive connection openings
    1398236 failed connection attempts
    111345 connection resets received
    83 connections established
    438293250 segments received
    508143650 segments sent out
    42567 segments retransmitted
    546 bad segments received
    329039 resets sent
Udp:
    1661295 packets received
    278 packets to unknown port received
    0 packet receive errors
    1545720 packets sent
    0 receive buffer errors
    0 send buffer errors
    IgnoredMulti: 33046
UdpLite:
TcpExt:
    1 invalid SYN cookies received
    1398196 resets received for embryonic SYN_RECV sockets
    1737473 packets pruned from receive queue because of socket buffer overrun
    1118775 TCP sockets finished time wait in fast timer
    638 time wait sockets recycled by time stamp
    656 packetes rejected in established connections because of timestamp
    2218959 delayed acks sent
    2330 delayed acks further delayed because of locked socket
    Quick ack mode was activated 7172 times
    271799723 packet headers predicted
    14917420 acknowledgments not containing data payload received
    171078735 predicted acknowledgments
    52 times recovered from packet loss due to fast retransmit
    TCPSackRecovery: 337
    Detected reordering 1551 times using SACK
    Detected reordering 1501 times using reno fast retransmit
    Detected reordering 61 times using time stamp
    9 congestion windows fully recovered without slow start
    38 congestion windows partially recovered using Hoe heuristic
    TCPDSACKUndo: 241
    104 congestion windows recovered without slow start after partial ack
    TCPLostRetransmit: 11550
    1 timeouts after reno fast retransmit
    TCPSackFailures: 13
    3772 fast retransmits
    2 retransmits in slow start
    TCPTimeouts: 24104
    TCPLossProbes: 101748
    TCPLossProbeRecovery: 134
    TCPSackRecoveryFail: 3
    128989224 packets collapsed in receive queue due to low socket buffer
    TCPBacklogCoalesce: 715034
    TCPDSACKOldSent: 7168
    TCPDSACKOfoSent: 341
    TCPDSACKRecv: 16612
    150689 connections reset due to unexpected data
    27063 connections reset due to early user close
    17 connections aborted due to timeout
    TCPDSACKIgnoredOld: 158
    TCPDSACKIgnoredNoUndo: 13514
    TCPSpuriousRTOs: 9
    TCPSackMerged: 1191
    TCPSackShiftFallback: 1011
    TCPDeferAcceptDrop: 699473
    TCPRcvCoalesce: 3311764
    TCPOFOQueue: 14289375
    TCPOFOMerge: 356
    TCPChallengeACK: 621
    TCPSYNChallenge: 621
    TCPSpuriousRtxHostQueues: 4
    TCPAutoCorking: 1605205
    TCPFromZeroWindowAdv: 132380
    TCPToZeroWindowAdv: 132441
    TCPWantZeroWindowAdv: 1445495
    TCPSynRetrans: 23652
    TCPOrigDataSent: 388992604
    TCPHystartTrainDetect: 69089
    TCPHystartTrainCwnd: 3264904
    TCPHystartDelayDetect: 4
    TCPHystartDelayCwnd: 128
    TCPACKSkippedPAWS: 3
    TCPACKSkippedSeq: 2001
    TCPACKSkippedChallenge: 2
    TCPWinProbe: 123043
    TCPKeepAlive: 4389
    TCPDelivered: 389507445
    TCPAckCompressed: 7343781
    TcpTimeoutRehash: 23311
    TcpDuplicateDataRehash: 8
    TCPDSACKRecvSegs: 17335
IpExt:
    InMcastPkts: 145100
    OutMcastPkts: 9429
    InBcastPkts: 18226
    InOctets: 722933727848
    OutOctets: 759502627470
    InMcastOctets: 58227095
    OutMcastOctets: 3284379
    InBcastOctets: 1756918
    InNoECTPkts: 440286946
    InECT0Pkts: 936

 

  • List all listening established connections to host

# netstat -ltne

  • List all UDP / TCP connections

# netstat -ltua

or if you prefer to do it with the newer and more comprehensive tool ss:
 

  • List all listening TCP connections 

# ss -lt

  • List all listening UDP connections 

# ss -ua

  • Display statistics about recent connections

root@pcfrxen:~# ss -s
Total: 329
TCP:   896 (estab 70, closed 769, orphaned 0, timewait 767)

Transport Total     IP        IPv6
RAW      0         0         0        
UDP      40        36        4        
TCP      127       118       9        
INET      167       154       13       
FRAG      0         0         0 

  • If you need to debug some specific sport or dport filter out the connection you need by port number

# ss -at '( dport = :22 or sport = :22 )'

 

Debug for any possible issues with ICMP unreachable but ports reachable with NMAP / telnet / Netcat
 

# nc 192.168.0.1 -vz

root@pcfrxen:/ # nc 192.168.0.1 80 -vz
pcfreak [192.168.0.1] 80 (http) open


root@pcfrxen:/ # nc 192.168.0.1 5555 -vz
pcfreak [192.168.0.1] 5555 (?) : Connection refused

 

root@pcfrxen:/# telnet 192.168.0.1 3128
Trying 192.168.0.1…
Connected to 192.168.0.1.
Escape character is '^]'.
^]
telnet> quit
Connection closed.

 

root@pcfrxen:/# nmap -sS -P0 192.168.0.1 -p 443 -O
Starting Nmap 7.80 ( https://nmap.org ) at 2023-11-27 19:51 EET
Nmap scan report for pcfreak (192.168.0.1)
Host is up (0.00036s latency).

PORT    STATE SERVICE
443/tcp open  https
MAC Address: 8C:89:A5:F2:E8:D8 (Micro-Star INT'L)
Warning: OSScan results may be unreliable because we could not find at least 1 open and 1 closed port
Aggressive OS guesses: Linux 3.11 (96%), Linux 3.1 (95%), Linux 3.2 (95%), AXIS 210A or 211 Network Camera (Linux 2.6.17) (94%), Linux 2.6.32 (94%), Linux 3.10 (94%), Linux 2.6.18 (93%), Linux 3.2 – 4.9 (93%), ASUS RT-N56U WAP (Linux 3.4) (93%), Linux 3.16 (93%)
No exact OS matches for host (test conditions non-ideal).
Network Distance: 1 hop

OS detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 6.24 seconds
root@pcfrxen:/# 

10. Add static MAC address to Ethernet Interface (if you find a MAC address being wrongly assigned to interface)

Sometimes problems with network unrechability between hosts is caused by wrongly defined MAC addresses on a Switch that did not correspond correctly to the ones assigned on the Linux host.
The easiest resolution here if you don't have access to Switch in work environment is to reassign the default MAC addresses of interfaces to proper MAC addresses, expected by remote router.

 

root@pcfrxen:/#  ​/sbin/ifconfig eth2 hw ether 8c:89:a5:f2:e8:d6

root@pcfrxen:/#  /sbin/ifconfig eth1 hw ether 8c:89:a5:f2:e8:d5

 

root@pcfrxen:/#  ifconfig eth0|grep -i ether
        ether 8c:89:a5:f2:e8:d6 txqueuelen 1000  (Ethernet)

 

11. Check for Network Address Translation (NAT) misconfigurations

If you do use some NAT-ing between Linux host and the remote Network Device you cannot reach, make sure IP Forwarding is enabled (i.e. /etc/sysctl.conf was not mistakenly overwritten by a script or admin for whatever reason).
 

root@server:~# sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 1
root@server:~# sysctl net.ipv4.conf.all.forwarding
net.ipv4.conf.all.forwarding = 1

root@server:~# sysctl net.ipv6.conf.all.forwarding
net.ipv6.conf.all.forwarding = 0

12. Check for Resolving DNS irregularities with /etc/resolv.conf


If network connectivity is okay on TCP / IP , UDP Level but problems with DNS of course, check what you have configured inside /etc/resolv.conf

And if use newer Linux distributions and have resolving managed by systemd check status of resolvectl
 

root@server:~# cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND — YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "resolvectl status" to see details about the actual nameservers.

nameserver 127.0.0.1
search pc-freak.net
domain pc-freak.net
nameserver 8.8.8.8
nameserver 8.8.4.4
nameserver 109.104.195.2
nameserver 109.104.195.1
nameserver 208.67.222.222
nameserver 208.67.220.220
options timeout:2 rotate

root@pcfreak:~# 

 

root@server:~# resolvectl status
Global
       Protocols: -LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub

Link 2 (ens3)
    Current Scopes: DNS
         Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 192.168.5.1
       DNS Servers: 192.168.5.1

 

  As seen see, the systemd-resolved service is used to provide domain names resolution and we can modify its configuration file /etc/systemd/resolved.conf to add the DNS server – the following line is set (two DNS servers’ addresses are added):

For example …

DNS=8.8.8.8 

13. Fix problems with wrongly configured Network Speed between hosts

It is not uncommon to have a Switch between two Linux hosts that is set to communicate on a certain maximum amount of Speed but a Linux host is set to communicate or lesser or more of Speed, this might create network issues so in such cases make sure either you use the Auto Negitionation network feature
or set both sides to be communicating on the same amount of network speed.

To turn on auto negotiation for ether interface 

# ethtool -s eth1 speed 1000 duplex full autoneg on


For example to set a Linux network interface to communicate on 1 Gigabit speed and switch off autonegotiation off.

# ethtool -s eth1 speed 1000 duplex full autoneg off

14. Check arp and icmp traffic with tcpdump

On both sides where the IPs can't see each other we can run a tcpdump to check the ARP and ICMP traffic flowing between the hosts.
 

# tcpdump -i eth1 arp or icmp

cpdump: verbose output suppressed, use -v[v]… for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), snapshot length 262144 bytes
15:29:07.001841 IP freak-eth1 > pcfr_hware_local_ip: ICMP echo request, id 13348, seq 65, length 64
15:29:07.001887 IP pcfr_hware_local_ip > freak-eth1: ICMP echo reply, id 13348, seq 65, length 64
15:29:07.598413 ARP, Request who-has pcfr_hware_local_ip tell zabbix-server, length 46
15:29:07.598425 ARP, Reply pcfr_hware_local_ip is-at 8c:89:a5:f2:e8:d8 (oui Unknown), length 28
15:29:07.633055 ARP, Request who-has freak_vivacom_auto_assigned_dhcp_ip tell 192.168.1.1, length 46
15:29:08.025824 IP freak-eth1 > pcfr_hware_local_ip: ICMP echo request, id 13348, seq 66, length 64
15:29:08.025864 IP pcfr_hware_local_ip > freak-eth1: ICMP echo reply, id 13348, seq 66, length 64

 

# tcpdump -i eth1 -vvv

 

If you want to sniff for TCP protocol and specific port and look up for DATA transfered for SMTP you can use something like:

 

# tcpdump -nNxXi eth0 -s 0 proto TCP and port 25​

 

If you need a bit more thorough explanation on what it would do check out my previous article How to catch / track mail server traffic abusers with tcpdump
 

15. Debugging network bridge issues

Having bridge network interface is another brink where things could go totally wrong.
If you have network bridges configured, check out what is the status of the bridge.
 

root@freak:/etc/network# brctl show
bridge name    bridge id        STP enabled    interfaces
xenbr0        8000.70e284134411    yes        eno1
                            vif1.0
                            vif10.0
                            vif16.0
                            vif16.0-emu
                            vif2.0
                            vif3.0
                            vif4.0
                            vif5.0
                            vif6.0
                            vif9.0
                            vif9.0-emu
xenbr1        8000.70e284134412    yes        eno2
                            vif1.1
                            vif10.1
                            vif16.1
                            vif16.1-emu
                            vif2.1
                            vif3.1
                            vif4.1
                            vif5.1
                            vif6.1
                            vif9.1
                            vif9.1-emu


Check out any configurations such as /etc/sysconfig/network-scripts/ifcfg-* are not misconfigured if on Redhat / CentOS / Fedora.
Or if on Debian / Ubuntu and other deb based Linuxes look up for /etc/network/interfaces config problems that might be causing the bridge to misbehave.

For example one bridge network issue, I've experienced recently is related to bridge_ports variable configured as bridge_ports all.
This was causing the second bridge xenbr1 to be unable to see another local network that was directly connected with a cable to it.

The fix was bridge_ports none. Finding out this trivial issue caused by a restored network config from old backup took me days to debug.
As everything seemed on a network level to be perfect just like in Physical layer, same way and on Software level, routings were okay.

Checked everything multiple times and did not see anything irregular. ping was missing and hosts cannot see each other even though having the right netmask and
network configuration in place.

Below is my /etc/network/interfaces configuration with the correct bridge_ports none changed.

root@freak:/etc/network# cat /etc/network/interfaces
auto lo
iface lo inet loopback
 

auto eno1
allow-hotplug eno1
iface eno1 inet manual
dns-nameservers 127.0.0.1 8.8.8.8 8.8.4.4 207.67.222.222 208.67.220.220
auto eno2
allow-hotplug eno2
iface eno2 inet manual
dns-nameservers 127.0.0.1 8.8.8.8 8.8.4.4 207.67.222.222 208.67.220.220

auto xenbr0
allow-hotplug xenbr0
 # Bridge setup
# fetching dhcp ip from 192.168.1.20 (vivacom fiber optics router) routing traffic via 1Gigabit network
 iface xenbr0 inet dhcp
    hwaddress ether 70:e2:84:13:44:11
#    address 192.168.1.5/22
    address 192.168.1.5
    netmask 255.255.252.0
    # address 192.168.1.8 if dhcp takes from vivacom dhcpd
    bridge_ports eno1
    gateway 192.168.1.20
    bridge_stp on
    bridge_waitport 0
    bridge_fd 0
    bridge_ports none
    dns-nameservers 8.8.8.8 8.8.4.4

auto xenbr1
# fetching dhcp ip from pc-freak.net (192.168.0.1) bergon.net routing traffic through it
allow-hotplug xenbr1
 iface xenbr1 inet dhcp
    hwaddress ether 70:e2:84:13:44:11
##    address 192.168.0.3/22
    address 192.168.0.8
    netmask 255.255.252.0
   # address 192.168.0.8 if dhcp takes from vivacom dhcpd (currently mac deleted from vivacom router)
   # address 192.168.0.9 if dhcp takes from pc-freak.net hware host
#    hwaddress ether 70:e2:84:13:44:13
    gateway 192.168.0.1
    bridge_ports eno2
    bridge_stp on
    bridge_waitport 0
    bridge_fd 0
    bridge_ports none
    dns-nameservers 8.8.8.8 8.8.4.4
root@freak:/etc/network# 
 

 

root@freak:/etc/network# brctl showstp xenbr0
xenbr0
 bridge id        8000.70e284134411
 designated root    8000.70e284134411
 root port           0            path cost           0
 max age          20.00            bridge max age          20.00
 hello time           2.00            bridge hello time       2.00
 forward delay          15.00            bridge forward delay      15.00
 ageing time           0.00
 hello timer           1.31            tcn timer           0.00
 topology change timer       0.00            gc timer           0.00
 flags            


eno1 (1)
 port id        8001            state             forwarding
 designated root    8000.70e284134411    path cost          19
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    8001            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

vif1.0 (2)
 port id        8002            state             forwarding
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    8002            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

vif10.0 (12)
 port id        800c            state             forwarding
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    800c            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

vif16.0 (13)
 port id        800d            state               disabled
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    800d            forward delay timer       0.00
 designated cost       0            hold timer           0.00
 flags            

vif16.0-emu (14)
 port id        800e            state             forwarding
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    800e            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

vif2.0 (4)
 port id        8004            state             forwarding
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    8004            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

vif3.0 (5)
 port id        8005            state             forwarding
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    8005            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

vif4.0 (3)
 port id        8003            state             forwarding
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    8003            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

vif5.0 (6)
 port id        8006            state             forwarding
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    8006            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

vif6.0 (7)
 port id        8007            state             forwarding
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    8007            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

vif9.0 (10)
 port id        800a            state               disabled
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    800a            forward delay timer       0.00
 designated cost       0            hold timer           0.00
 flags            

vif9.0-emu (11)
 port id        800b            state             forwarding
 designated root    8000.70e284134411    path cost         100
 designated bridge    8000.70e284134411    message age timer       0.00
 designated port    800b            forward delay timer       0.00
 designated cost       0            hold timer           0.31
 flags            

root@freak:/etc/network# 


Sum it up

We have learned how to debug various routing issues, how to add and remote default gateways, check network reachability with ICMP protocol with ping, traceroute as well check for DNS issues and given some hints how to resolve DNS misconfigurations.
We also learned how to check the configured Network interfaces certain settings and resolve issues caused by Network sides max Speed misconfigurations as well how to track and resolve communication issues caused by wrongly configured MAC addresses.
Further more learned on how to do a basic port and protocol debugging of state of Network packets with netstat and nc and check problems related to iptables Firewall and IP Forwarding misconfigurations.
Finally we learned some basic usage of tcpdump on how to track arp and MAC traffic and look up for a specific TCP / UDP protocol  and its contained data.
There is certainly things this article is missing as the topic of debugging network connectivity issues on Linux is a whole ocean, especially as the complexity of Linux has grown dramatically these days.
I gues it is worthy to mention that unable to see remote network could be caused by wrong VLAN configurations on Linux or even buggy switches and router devices, due to hardware or software,
but I hope this article at least covers the very basics of network debugging and Linux. 

Enjojy 🙂

How to turn On or Off Screen Reader ORCA on Linux Desktop enabled by mistype or a kid smash on the keyboard

Wednesday, November 22nd, 2023

orca-screen-reader-communication-services-logo

For those who type quite fast and use Microsoft Windows, its quite common to start the annoying NARRATOR (Windows Speaking Program) by accidently due to mistyping pressing together Windows key + Control + Enter.
This enables Narrator to read stuff on the screen here and there and to turn it off you just have to either Lock the Windows Computer and press again Windows key + Control + Enter to TURN OFF NARRATOR.

Linux does not have a Narrator but have also embedded Eye impairment Assistive Technology called ORCA.

Orca works with applications and toolkits that support the Assistive Technology Service Provider Interface (AT-SPI), which is the primary assistive technology infrastructure for Linux and Solaris. Applications and toolkits supporting the AT-SPI include the GNOME Gtk+ toolkit, the Java platform's Swing toolkit, LibreOffice, Gecko, and WebKitGtk. AT-SPI support for the KDE Qt toolkit is being pursued.

ORCA is nowadays installed and integrated into many if not most Linux distributions out there. Enabling ORCA is not such a common thing on Linux,so today I got quite puzzled once I came back to the computer, leaving the 3.7 months kid near the Keyboard and finding out that I've enabled aloud screen reader that is reading what is every Window / Menu / Program or object I select with the mouse on my Linux MATE Desktop home GUI environment running on top of Debian Linux.

After a quick look up in Google on what exactly is the Linux program that is reading my screen I came across ORCA, which seem to be visible also as running in my process list:

hipo@jeremiah:~/Downloads$ ps -ef|grep -i orca
hipo     1068376    7960 17 18:48 tty2     00:00:01 orca

After a quick check online I found out that,

To start (Turn On ) Orca Screen Reader using the keyboard:

Windows logo button (Super Key) key + Alt + S 

Of course, it is possible to shut off the annoying reader by simply killing it with:

kill -9 orca

 

Ubuntu users, could start Orca using a mouse and keyboard:

Open the Activities overview and start typing Accessibility.

Click Accessibility to open the panel.

Select thez to open it.

Switch the Screen Reader switch to on.

Problem solved now Screen Reader on Linux is disabled, maybe it is time to disable Orca key press ability to prevent the kid from enabling it again since I don't need it actively thanksfully. with

xmodmap -e 'keycode <value>='

or simply removing the orca package with apt:

# apt remove orca

Resize KVM .img QCOW Image file and Create new LVM partition and ext4 filesystem inside KVM Virtual Machine

Friday, November 10th, 2023

LVM-add-space-to-RHEL-Linux-on-KVM_Virtual_machine-howto

Part of migration project for a customer I'm working on is migration of a couple of KVM based Guest virtual machine servers. The old machines has a backup solution stratetegy using IBM's TSM and the new Machines should use the Cheaper solution adopted by the Customer company using the CommVault backup solution (an enterprise software thath is used for data backup and recovery not only to local Tape Library / Data blobs on central backup servers infra but also in Cloud infrastructure.

To install the CommVault software on the Redhat Linux-es, the official install documentation (prepared by the team who prepared the CommVault) infrastructure for the customer recommends to have a separate partition for the CommVault backups under /opt directory  (/opt/commvault) and the partition should be as a minumum at least 10 Gigabytes of size. 

Unfortunately on our new prepared KVM VM guest machines, it was forgotten to have the separate /opt of 10GB prepared in advanced. And we ended up with Virtual Machines that has a / (root directory) of 68GB size and a separate /var and /home LVM parititons. Thus to correct the issues it was required to find a way to add another separate LVM partition inside the KVM VirtualMachine.img (QCOW Image file). 

This seemed to be an easy task at first as that might be possible with simple .img partition mount with losetup command kpartx and simple lvreduce command in some way such as

# mount /dev/loop0 /mnt/test/

# kpartx -a /dev/loop0
# kpartx -l /dev/loop0
# ls -al /dev/mapper/*

… 

# lvreduce 

etc. however unfortunately kpartx though not returning error did not provided the new /dev/mapper devices to be used with LVM tools and this approach seems to not be possible on RHEL 8.8 as the kpartx couldn't list.

 

A colleague of mine Mr. Paskalev suggested that we can perhaps try to mount the partition with default KVM tool to mount .img partitions which is guestmount but unfortunately
with a command like:
 

# guestmount -a /kvm/VM.img -i –rw /mnt/test/

But unfortunately this mounted the filesystem in fuse filesystem and the LVM /dev/mapper of the VM can't be seen so we decided to abondon this method.

After some pondering with Dimitar Paskalev and Dimitar Hristov, thanks to joint efforts we found the way to do it, below are the steps we followed to succeed in creating new LVM ext4 partition required.
One would wonder how many system
 

1. Check enough space is available on the HV machine

 

The VMs are held under /kvm so in this case:

[root@hypervisor-host ~]# df -h|grep -i /kvm
/dev/mapper/vg00-vmprivate  206G   27G  169G  14% /kvm

 

2. Shutdown the running VM and make sure it is stopped
 

[root@hypervisor-host ~]# virsh shutdown vm-host

 

[root@hypervisor-host ~]# virsh list –all
 Id   Name       State
————————–
 4    lpdkv01f   running
 5    vm-host   shut off

 

3. Check current Space status of VM

 

[root@hypervisor-host ~]# qemu-img info /kvm/vm-host.img       
image: /kvm/vm-host.img
file format: qcow2
virtual size: 100 GiB (107374182400 bytes)
disk size: 8.62 GiB
cluster_size: 65536
Format specific information:
    compat: 1.1
    compression type: zlib
    lazy refcounts: true
    refcount bits: 16
    corrupt: false
    extended l2: false

 

4. Resize (extend VM) with whatever size you want    
 

[root@hypervisor-host ~]# qemu-img resize /kvm/vm-host.img +10G

 

5. Start VM    
 

[root@hypervisor-host ~]# virsh start vm-host


7. Check the LVM and block devices on HVs (not necessery but good for an overview)
 

[root@hypervisor-host ~]# pvs
  PV         VG   Fmt  Attr PSize   PFree 
  /dev/sda2  vg00 lvm2 a–  277.87g 19.87g
  
[root@hypervisor-host ~]# vgs
  VG   #PV #LV #SN Attr   VSize   VFree 
  vg00   1  11   0 wz–n- 277.87g 19.87g

 

[root@hypervisor-host ~]# lsblk 
NAME               MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda                  8:0    0 278.9G  0 disk 
├─sda1               8:1    0     1G  0 part /boot
└─sda2               8:2    0 277.9G  0 part 
  ├─vg00-root      253:0    0    15G  0 lvm  /
  ├─vg00-swap      253:1    0     1G  0 lvm  [SWAP]
  ├─vg00-var       253:2    0     5G  0 lvm  /var
  ├─vg00-spool     253:3    0     2G  0 lvm  /var/spool
  ├─vg00-audit     253:4    0     3G  0 lvm  /var/log/audit
  ├─vg00-opt       253:5    0     2G  0 lvm  /opt
  ├─vg00-home      253:6    0     5G  0 lvm  /home
  ├─vg00-tmp       253:7    0     5G  0 lvm  /tmp
  ├─vg00-log       253:8    0     5G  0 lvm  /var/log
  ├─vg00-cache     253:9    0     5G  0 lvm  /var/cache
  └─vg00-vmprivate 253:10   0   210G  0 lvm  /vmprivate

  
8 . Check logical volumes on Hypervisor host
 

[root@hypervisor-host ~]# lvdisplay 
  — Logical volume —
  LV Path                /dev/vg00/swap
  LV Name                swap
  VG Name                vg00
  LV UUID                3tNa0n-HDVw-dLvl-EC06-c1Ex-9jlf-XAObKm
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:45 +0200
  LV Status              available
  # open                 2
  LV Size                1.00 GiB
  Current LE             256
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:1
   
  — Logical volume —
  LV Path                /dev/vg00/var
  LV Name                var
  VG Name                vg00
  LV UUID                JBerim-fxVv-jU10-nDmd-figw-4jVA-8IYdxU
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:45 +0200
  LV Status              available
  # open                 1
  LV Size                5.00 GiB
  Current LE             1280
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:2
   
  — Logical volume —
  LV Path                /dev/vg00/spool
  LV Name                spool
  VG Name                vg00
  LV UUID                nFlmp2-iXg1-tFxc-FKaI-o1dA-PO70-5Ve0M9
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:45 +0200
  LV Status              available
  # open                 1
  LV Size                2.00 GiB
  Current LE             512
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:3
   
  — Logical volume —
  LV Path                /dev/vg00/audit
  LV Name                audit
  VG Name                vg00
  LV UUID                e6H2OC-vjKS-mPlp-JOmY-VqDZ-ITte-0M3npX
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:46 +0200
  LV Status              available
  # open                 1
  LV Size                3.00 GiB
  Current LE             768
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:4
   
  — Logical volume —
  LV Path                /dev/vg00/opt
  LV Name                opt
  VG Name                vg00
  LV UUID                oqUR0e-MtT1-hwWd-MhhP-M2Y4-AbRo-Kx7yEG
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:46 +0200
  LV Status              available
  # open                 1
  LV Size                2.00 GiB
  Current LE             512
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:5
   
  — Logical volume —
  LV Path                /dev/vg00/home
  LV Name                home
  VG Name                vg00
  LV UUID                ehdsH7-okS3-gPGk-H1Mb-AlI7-JOEt-DmuKnN
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:47 +0200
  LV Status              available
  # open                 1
  LV Size                5.00 GiB
  Current LE             1280
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:6
   
  — Logical volume —
  LV Path                /dev/vg00/tmp
  LV Name                tmp
  VG Name                vg00
  LV UUID                brntSX-IZcm-RKz2-CP5C-Pp00-1fA6-WlA7lD
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:47 +0200
  LV Status              available
  # open                 1
  LV Size                5.00 GiB
  Current LE             1280
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:7
   
  — Logical volume —
  LV Path                /dev/vg00/log
  LV Name                log
  VG Name                vg00
  LV UUID                ZerDyL-birP-Pwck-yvFj-yEpn-XKsn-sxpvWY
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:47 +0200
  LV Status              available
  # open                 1
  LV Size                5.00 GiB
  Current LE             1280
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:8
   
  — Logical volume —
  LV Path                /dev/vg00/cache
  LV Name                cache
  VG Name                vg00
  LV UUID                bPPfzQ-s4fH-4kdT-LPyp-5N20-JQTB-Y2PrAG
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:48 +0200
  LV Status              available
  # open                 1
  LV Size                5.00 GiB
  Current LE             1280
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:9
   
  — Logical volume —
  LV Path                /dev/vg00/root
  LV Name                root
  VG Name                vg00
  LV UUID                mZr3p3-52R3-JSr5-HgGh-oQX1-B8f5-cRmaIL
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-08-07 13:47:48 +0200
  LV Status              available
  # open                 1
  LV Size                15.00 GiB
  Current LE             3840
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:0
   
  — Logical volume —
  LV Path                /dev/vg00/vmprivate
  LV Name                vmprivate
  VG Name                vg00
  LV UUID                LxNRWV-le3h-KIng-pUFD-hc7M-39Gm-jhF2Aj
  LV Write Access        read/write
  LV Creation host, time hypervisor-host, 2023-09-18 11:54:19 +0200
  LV Status              available
  # open                 1
  LV Size                210.00 GiB
  Current LE             53760
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  – currently set to     8192
  Block device           253:10

9. Check Hypervisor existing partitions and space
 

[root@hypervisor-host ~]# fdisk -l
Disk /dev/sda: 278.9 GiB, 299439751168 bytes, 584843264 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x0581e6e2

Device     Boot   Start       End   Sectors   Size Id Type
/dev/sda1  *       2048   2099199   2097152     1G 83 Linux
/dev/sda2       2099200 584843263 582744064 277.9G 8e Linux LVM


Disk /dev/mapper/vg00-root: 15 GiB, 16106127360 bytes, 31457280 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-swap: 1 GiB, 1073741824 bytes, 2097152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-var: 5 GiB, 5368709120 bytes, 10485760 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-spool: 2 GiB, 2147483648 bytes, 4194304 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-audit: 3 GiB, 3221225472 bytes, 6291456 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-opt: 2 GiB, 2147483648 bytes, 4194304 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-home: 5 GiB, 5368709120 bytes, 10485760 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-tmp: 5 GiB, 5368709120 bytes, 10485760 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-log: 5 GiB, 5368709120 bytes, 10485760 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-cache: 5 GiB, 5368709120 bytes, 10485760 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/vg00-vmprivate: 210 GiB, 225485783040 bytes, 440401920 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

 

10. List block devices on VM
 

[root@vm-host ~]# lsblk 
NAME               MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0                 11:0    1 1024M  0 rom  
vda                252:0    0  100G  0 disk 
├─vda1             252:1    0    1G  0 part /boot
├─vda2             252:2    0   88G  0 part 
│ ├─vg00-root      253:0    0   68G  0 lvm  /
│ ├─vg00-home      253:2    0   10G  0 lvm  /home
│ └─vg00-var       253:3    0   10G  0 lvm  /var
├─vda3             252:3    0    1G  0 part [SWAP]
└─vda4             252:4    0   10G  0 part 

 

 

11. Create new LVM partition with fdisk or cfdisk
 

If there is no cfdisk new resized space with qemu-img could be setup with a fdisk, though I personally always prefer to use cfdisk

[root@vm-host ~]# fdisk /dev/vda
# > p (print)
# > m (manfile)
# > n
# … follow on screen instructions to select start and end blocks
# > t (change partition type)
# > select and set to 8e
# > w (write changes)

[root@vm-host ~]# cfdisk /dev/vda


Setup new partition from Free space as [ primary ] partition and Choose to be of type LVM


12. List partitions to make sure new LVM partition is present
 

[root@vm-host ~]# fdisk -l
Disk /dev/vda: 100 GiB, 107374182400 bytes, 209715200 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xe7b2d9fd

Device     Boot     Start       End   Sectors Size Id Type
/dev/vda1  *         2048   2099199   2097152   1G 83 Linux
/dev/vda2         2099200 186646527 184547328  88G 8e Linux LVM
/dev/vda3       186646528 188743679   2097152   1G 82 Linux swap / Solaris
/dev/vda4       188743680 209715199  20971520  10G 8e Linux LVM

The extra added 10 Giga is seen under /dev/vda4.
  — Physical volume —
  PV Name               /dev/vda4
  VG Name               vg01
  PV Size               10.00 GiB / not usable 4.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              2559
  Free PE               0
  Allocated PE          2559
  PV UUID               yvMX8a-sEka-NLA7-53Zj-fFdZ-Jd2K-r0Db1z
   
  — Physical volume —
  PV Name               /dev/vda2
  VG Name               vg00
  PV Size               <88.00 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              22527
  Free PE               0
  Allocated PE          22527
  PV UUID               i4UpGr-h9Cd-iKBu-KqEI-15vK-CGc1-DwRPj8
   
[root@vm-host ~]# 

 

13. List LVM Physical Volumes
 

[root@vm-host ~]# pvdisplay 
  — Physical volume —
  PV Name               /dev/vda2
  VG Name               vg00
  PV Size               <88.00 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              22527
  Free PE               0
  Allocated PE          22527
  PV UUID               i4UpGr-h9Cd-iKBu-KqEI-15vK-CGc1-DwRPj8

 


  
  Notice the /dev/vda4 is not seen in pvdisplay (Physical Volume display command) because not created yet, so lets create it.
 

14. Initialize new Physical Volume to be available for use by LVM
 

[root@vm-host ~]# pvcreate /dev/vda4


15. Inform the OS for partition table changes
 

If partprobe is not available as command on the host, below obscure command should do the trick.
 

[root@vm-host ~]# echo "- – -" | tee /sys/class/scsi_host/host*/scan

However usually, better to use partprobe to inform the Operating System of partition table changes

[root@vm-host ~]# partprobe


16. Use lsblk again to see the new /dev/vda4 LVM is listed into "vda" root block device
 

[root@vm-host ~]# 
[root@vm-host ~]# lsblk
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0            11:0    1 1024M  0 rom  
vda           252:0    0  100G  0 disk 
├─vda1        252:1    0    1G  0 part /boot
├─vda2        252:2    0   88G  0 part 
│ ├─vg00-root 253:0    0   68G  0 lvm  /
│ ├─vg00-home 253:1    0   10G  0 lvm  /home
│ └─vg00-var  253:2    0   10G  0 lvm  /var
├─vda3        252:3    0    1G  0 part [SWAP]
└─vda4        252:4    0   10G  0 part 
[root@vm-host ~]# 


17. Create new Volume Group (VG) on /dev/vda4 block device
 

Before creating a new VG, list what kind of VG is on the machine to be sure the new created one will not be already present.
 

[root@vm-host ~]# vgdisplay 
  — Volume group —
  VG Name               vg00
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <88.00 GiB
  PE Size               4.00 MiB
  Total PE              22527
  Alloc PE / Size       22527 / <88.00 GiB
  Free  PE / Size       0 / 0   
  VG UUID               oyo1oY-saSm-0IKk-gZnf-Knwz-utO7-Aw8c60

vg00 is existing only, so we can use vg01 as a Volume Group name for the new volume group where the fresh 10GB LVM partition will lay

[root@vm-host ~]# vgcreate vg01 /dev/vda4
  Volume group "vg01" successfully created

 

18. Create new Logical Volume (LV) and extend it to occupy the full space available on Volume Group vg01

 

 

[root@vm-host ~]# lvcreate -n commvault -l 100%FREE vg01
  Logical volume "commvault" created.

  An alternative way to create the same LV is by running:

lvcreate -n commvault -L 10G vg01


19. Relist block devices with lsblk to make sure the new created Logical Volume commvault is really present and seen, in case of it missing re-run again partprobe cmd
 

[root@vm-host ~]# lsblk 
NAME               MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0                 11:0    1 1024M  0 rom  
vda                252:0    0  100G  0 disk 
├─vda1             252:1    0    1G  0 part /boot
├─vda2             252:2    0   88G  0 part 
│ ├─vg00-root      253:0    0   68G  0 lvm  /
│ ├─vg00-home      253:1    0   10G  0 lvm  /home
│ └─vg00-var       253:2    0   10G  0 lvm  /var
├─vda3             252:3    0    1G  0 part [SWAP]
└─vda4             252:4    0   10G  0 part 
  └─vg01-commvault 253:3    0   10G  0 lvm  

 

As it is not mounted yet, the VG will be not seen in df free space but will be seen as a volume group with vgdispaly
 

[root@vm-host ~]# df -h
Filesystem                  Size  Used Avail Use% Mounted on
devtmpfs                    2.8G     0  2.8G   0% /dev
tmpfs                       2.8G   33M  2.8G   2% /dev/shm
tmpfs                       2.8G   17M  2.8G   1% /run
tmpfs                       2.8G     0  2.8G   0% /sys/fs/cgroup
/dev/mapper/vg00-root        67G  2.4G   61G   4% /
/dev/mapper/vg00-var        9.8G 1021M  8.3G  11% /var
/dev/mapper/vg00-home       9.8G   24K  9.3G   1% /home
/dev/vda1                   974M  242M  665M  27% /boot
tmpfs                       569M     0  569M   0% /run/user/0

 

[root@vm-host ~]# vgdisplay 
  — Volume group —
  VG Name               vg01
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <10.00 GiB
  PE Size               4.00 MiB
  Total PE              2559
  Alloc PE / Size       2559 / <10.00 GiB
  Free  PE / Size       0 / 0   
  VG UUID               nYP0tv-IbFw-fBVT-slBB-H1hF-jD0h-pE3V0S
   
  — Volume group —
  VG Name               vg00
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <88.00 GiB
  PE Size               4.00 MiB
  Total PE              22527
  Alloc PE / Size       22527 / <88.00 GiB
  Free  PE / Size       0 / 0   
  VG UUID               oyo1oY-saSm-0IKk-gZnf-Snwz-utO7-Aw8c60
  


20. Create new ext4 filesystem on the just created vg01-commvault   
 

[root@vm-host ~]# mkfs.ext4 /dev/mapper/vg01-commvault 

[root@vm-host ~]# mkfs.ext4 /dev/mapper/vg01-commvault 
mke2fs 1.45.6 (20-Mar-2020)
Discarding device blocks: done                            
Creating filesystem with 2620416 4k blocks and 655360 inodes
Filesystem UUID: 1491d8b1-2497-40fe-bc40-5faa6a2b2644
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done 


21. Mount vg01-commvault into /opt directory
 

[root@vm-host ~]# mkdir -p /opt/

[root@vm-host ~]# mount /dev/mapper/vg01-commvault /opt/


22. Check mount is present on VM guest OS
 

[root@vm-host ~]# mount|grep -i /opt
/dev/mapper/vg01-commvault on /opt type ext4 (rw,relatime)
[root@vm-host ~]# 

[root@vm-host ~]# df -h|grep -i opt
/dev/mapper/vg01-commvault  9.8G   24K  9.3G   1% /opt
[root@vm-host ~]# 
 

23. Add vg01-commvault to be auto mounted via /etc/fstab on next Virtual Machine reboot
 

[root@vm-host ~]# echo '/dev/mapper/vg01-commvault /opt         ext4            defaults        1        2' >> /etc/fstab

[root@vm-host ~]# rpm -ivh commvault-fs.Instance001-11.0.0-80.240.0.3589820.240.4083067.el8.x86_64.rpm

[root@vm-host ~]# systemctl status commvault
● commvault.Instance001.service – commvault Service
   Loaded: loaded (/etc/systemd/system/commvault.Instance001.service; enabled; vendor preset: disabled)
   Active: active (running) since Fri 2023-11-10 15:13:59 CET; 27s ago
  Process: 9972 ExecStart=/opt/commvault/Base/Galaxy start direct -focus Instance001 (code=exited, status=0/SUCCESS)
    Tasks: 54
   Memory: 155.5M
   CGroup: /system.slice/commvault.Instance001.service
           ├─10132 /opt/commvault/Base/cvlaunchd
           ├─10133 /opt/commvault/Base/cvd
           ├─10135 /opt/commvault/Base/cvfwd
           └─10137 /opt/commvault/Base/ClMgrS

Nov 10 15:13:57 vm-host.ffm.de.int.atosorigin.com systemd[1]: Starting commvault Service…
Nov 10 15:13:58 vm-host.ffm.de.int.atosorigin.com Galaxy[9972]: Cleaning up /opt/commvault/Base/Temp …
Nov 10 15:13:58 vm-host.ffm.de.int.atosorigin.com Galaxy[9972]: Starting Commvault services for Instance001 …
Nov 10 15:13:59 vm-host.ffm.de.int.atosorigin.com Galaxy[9972]: [22B blob data]
Nov 10 15:13:59 vm-host.ffm.de.int.atosorigin.com systemd[1]: Started commvault Service.
[root@vm-host ~]# 

 

24. Install Commvault backup client RPM in new mounted LVM under /opt

[root@vm-host ~]#  rpm -ivh commvault.rpm

Simple bash shell Script to easy and quickly automate deploy RHEL Linux Virtual Machines on KVM Virtualization

Friday, November 3rd, 2023

how-to-install-a-kvm-guest-os-from-the-commandline-easily-with-script-virt-install-logo

Earlier I've blogged in about howto build KVM Virtual Machine RHEL 8.3 Linux install on Redhat 8.3 Linux Hypervisor with custom tailored kickstart.cfg as one of the Projects i was involved in my work duty as system administrator, we had the task to build
a KVM virtual machines and build a High Availability Linux  PCS Corosync / Pacemaker / haproxy cluster on it to save some money for the company from purchasing VMWare licenses.

The setup of the KVM Virtual machine on a first glimpse is relatively simple and I thought, this can be done just for 2 / 3 days but it turned out to take up 2 weeks or so to properly prepare the kickstarter file and learn a bit about basic virt-install KVM options and experiment with them until
we can produce a noral working Virtual machines. 

The original developed simple script that I used to bring up a new KVM virtual machines in a bit easier way virt-install-kvm.sh looked like so:
 

#!/bin/sh
# Script to build a new VM based on a kickstart.cfg file template
# with virt-install
# Author Georgi Georgiev hip0
# hipo@Pc-freak.net

KS_FILE='kickstart.cfg';
VM_NAME='RHEL8_3-VirtualMachine';
VM_DESCR='CentOS 8.3 Virtual Machine';
RAM='8192';
CPUS='8';
# size is in Gigabytes
VM_IMG_SIZE='70';
ISO_LOCATION='/vmprivate/rhel-server-8.3-x86_64-dvd.iso';
VM_IMG_FILE_LOC='/vmprivate/RHEL8_3-VirtualMachine.img';

virt-install -n "$VMNAME" –description "$VM_DESCR" –os-type=Linux –os-variant=rhel8.3 –ram=8192 –vcpus=8 –location="$ISO_LOCATION" –disk path=$VM_IMG_FILE,bus=virtio,size=$IMG_VM_SIZE –graphics none –initrd-inject=/root/$KS_FILE –extra-args "console=ttyS0 ks=file:/$KS_FILE"

 

The script basicly did what it was aimed for but modifying the kickstarter ks.cfg every time with multiple additional parameters, like network configurations as well some additional modifications to ks.cfg for VM parameters was annoying.

Recently as we had to repeat the same task again in order to migrate old customer containing a Linux OpenVZ Virtual machines to a newer  OS installed RHEL versionb with KVM virtual machines, i've took some hours and scripted a small script that would easiy our task to build new KVM Virtual Machines
from scratch relatively easy, if we have to repeat the Linux OS build operation again and again.

Before proceeding to use the script of course one has to use LVM and setup the partitions on the Host which will be the Hypervisor where the KVM VMs will be installed as well you need to download an ISO image of Redhat Enterprise Linux / CentOS / Fedora or whatever kind of RPM based Linux
you would like to setup as well as do the basic configurations regarding the emulated Hardware node "Power" of the new Virtual Machine (CPU / Memory / Disk Partition) as well as choose a proper meaningful VM name (preferrably following some good meaningful crafted naming convention, that will talk a bit about what is inside the KVM VM container).

The script that automates a bit the KVM VM installation which you find below you can also download from here virt-install.sh

 

#!/bin/bash
virt_install_path=$(which virt-install);
vm_host='vmname01';
boot_iso='/vmprivate/rhel-8.7-x86_64-dvd.iso';
os_version='rhel8.7';
vm_cpus_count='4';
vm_ram='6144';
vm_img_location='/vmprivate/NAME-of-VM.img';
vm_machine_description='Name Production system';
ks_file_location_template='/root/ks.cfg.templ';
ks_file_location='/root/ks.cfg';
ks_vm_read_loc=$(echo $ks_file_location |sed -e 's#root/##g');
vm_main_ip='192.168.23.52';
vm_netmask='255.255.255.192';
vm_gateway='192.168.23.33';
vm_nameserver='172.30.50.2';
#–ip=192.168.233.52 –netmask=255.255.255.192 –gateway=192.168.233.33 –nameserver=172.20.88.2

echo "Checking if defined $vm_host image $vm_img_location is not already present";
if [ ! -f $vm_img_location ]; then
echo
else
echo 'Exiting $vm_img_location is present';
echo "To destroy exiting VM image $vm_img_location run manually cmds:";
echo 'virsh list; virsh destroy $vm_host; virsh undefine $vm_host –remove-all-storage';
exit 1;
fi

alias cp='cp -f';
/usr/bin/cp -rpf $ks_file_location_template $ks_file_location;

echo "Setting  VM Main IP: $vm_main_ip";
echo "Setting  VM netmask: $vm_netmask";
echo "Setting  VM Gateway: $vm_gateway";
echo "Setting  VM Nameserver $vm_nameserver";
/usr/bin/perl -pi -e "s/ip=a1.a2.a3.a4/ip=$vm_main_ip/" $ks_file_location
/usr/bin/perl -pi -e "s/netmask=b1.b2.b3.b4/netmask=$vm_netmask/" $ks_file_location
/usr/bin/perl -pi -e "s/gateway=c1.c2.c3.c4/nameserver=$vm_nameserver/" $ks_file_location
/usr/bin/perl -pi -e "s/nameserver=d1.d2.d3.d4/gateway=$vm_gateway/" $ks_file_location
/usr/bin/perl -pi -e "s/vm-hostname/$vm_host/" $ks_file_location

echo "Running VM install:";
echo $virt_install_path -n $vm_host –description "$vm_machine_description" –os-type=Linux –os-variant=$os_version –ram=$vm_ram –vcpus=$vm_cpus_count –location=$boot_iso –disk path=$vm_img_location,bus=virtio,size=90 –graphics none –initrd-inject=$ks_file_location –extra-args "console=ttyS0 ks=file:$ks_vm_read_loc"

$virt_install_path -n $vm_host –description "$vm_machine_description" –os-type=Linux –os-variant=$os_version –ram=$vm_ram –vcpus=$vm_cpus_count –location=$boot_iso –disk path=$vm_img_location,bus=virtio,size=90 –graphics none –initrd-inject=$ks_file_location –extra-args "console=ttyS0 ks=file:$ks_vm_read_loc"
 

 

Modify the script to insert the required parameters of the new VM in the script header session, you will have to provide below options.

 

vm_host='vmname01';
boot_iso='/vmprivate/rhel-8.7-x86_64-dvd.iso';
os_version='rhel8.7';
vm_cpus_count='4';
vm_ram='6144';
vm_img_location='/vmprivate/NAME-of-VM.img';
vm_machine_description='Name Production system';
ks_file_location_template='/root/ks.cfg.templ';
ks_file_location='/root/ks.cfg';
ks_vm_read_loc=$(echo $ks_file_location |sed -e 's#root/##g');
vm_main_ip='192.168.23.52';
vm_netmask='255.255.255.192';
vm_gateway='192.168.23.33';
vm_nameserver='172.30.50.2';

The automatic Build virtual machine script is tested and works with Redhat Enterprise Linux and of course is pretty primitive as there is so much available online that would do similar, but still I like it because it works for me 🙂

You will need also the ks.cfg.templ file which has the basic kickstarter configuration that will bring up the Virtual machines according to predefined configurations.
Here is the ks.cfg.templ and ks.cfg files as well, you will have to place them under /root/ or some other directory.
Of course this script is just a basic one, it can be easily updated to accept its variable options as arguments if you need to bring up a multitude of virtual machines relatively quickly with few minor modifications. 

Hope the script is helpful to some sysadmin out there. If so don't forget to donate me for a beer in my Patreon account found in the widgets section 🙂

Check the Type and Model of available installed Memory on Linux / Unix / BSD Server howto

Monday, October 30th, 2023

how-linux-kernel-manages-memory-picture

As a system administrator one of the common task, one has to do is Add / Remove or Replace (of Broken or failing Bank of RAM memory) a piece of additional Bank of memory Bank to a Linux / BSD / Unix server.  Lets say you need to fullfil the new RAM purchase and provide some information to the SDM (Service Delivery Manager) of the compnay you're hirder in or you need to place the purchase yourself. Then you  need to know the exact speed and type of RAM currently installed on the server installed.

In this article i'll shortly explain how do I find out ram (SDRAM) information from a via ordinary remote ssh shell session cmd prompt. In short will be shown how can one check RAM speed configured and detected by Linux / Unix kernel ? 
As well as  how to Check the type of memory (if it is DDR / DDR2 / DDR or DDR4) or ECC with no access to Hardware Console.  Please note this article will be definitely boring for the experienced sysadmins but might help to a starter sysadmins to get on board with a well know basic stuff.

There are several approaches, of course easiest one is to use remote hardware access interrace statistics web interface of ILO (on IBM machine) or the IDRAC on (Dell Server) or Fujitsu's servers iRMC. However as not always access to remote Remote hardware management interface is available to admin. Linux comes with few commands that can do the trick, that are available to most Linux distributions straight for the default package repositories.

Since mentioning about ECC a bit up, most old school admins and computer users knows pretty well about DDRs as they have been present over time but ECC is being used over actively on servers perhaps over the last 10 / 15 years and for those not dealt with it below is a short description on what is ECC RAM Memory.

ECC RAM, short for Error Correcting Code Random Access Memory, is a kind of RAM can detect most common kinds of memory errors and correct a subset of them. ECC RAM is common in enterprise deployments and most server-class hardware. Above a certain scale and memory density, single-bit errors which were up to this point are sufficiently statistically unlikely begin to occur with enough frequency that they can no longer be ignored. At certain scales and densities of memory arbitrary memory errors that are literally "one in a million chances" (or more) may in fact occur several times throughout a system's operational life.

Putting some basics, Lets proceed and Check RAM speed and type (line DDR or DDR2 or DDR3 or DDR4) without having to physically go to the the Data Center numbered rack that is containing the server.


Most famous and well known (also mentioned) on few occasions in my previous articles are: dmidecode and lshw

Quickest way to get a quick overview of installed servers memory is with:
 

root@server:~# dmidecode -t memory | grep -E "Speed:|Type:" | sort | uniq -c
      4     Configured Memory Speed: 2133 MT/s
     12     Configured Memory Speed: Unknown
      4     Error Correction Type: Multi-bit ECC
      2     Speed: 2133 MT/s
      2     Speed: 2400 MT/s
     12     Speed: Unknown
     16     Type: DDR4

 

To get more specifics on the exact type of memory installed on the server, the respective slots that are already taken and the free ones:

root@server:~# dmidecode –type 17 | less

Usually the typical output the command would produce regarding lets say 4 installed Banks of RAM memory on the server will be like:

Handle 0x002B, DMI type 17, 40 bytes
Memory Device
        Array Handle: 0x0029
        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
       
Size: 16 GB
        Form Factor: RIMM
        Set: None
        Locator: CPU1 DIMM A1
        Bank Locator: A1_Node0_Channel0_Dimm1
       
Type: DDR4
        Type Detail: Synchronous
       
Speed: 2400 MT/s
        Manufacturer: Micron
       
Serial Number: 15B36358
        Asset Tag: CPU1 DIMM A1_AssetTag
       
Part Number: 18ASF2G72PDZ-2G3B1 
        Rank: 2
       
Configured Memory Speed: 2133 MT/s
        Minimum Voltage: Unknown
        Maximum Voltage: Unknown
        Configured Voltage: Unknown

Handle 0x002E, DMI type 17, 40 bytes
Memory Device
        Array Handle: 0x0029
        Error Information Handle: Not Provided
        Total Width: Unknown
        Data Width: Unknown
        Size: No Module Installed
        Form Factor: RIMM
        Set: None
        Locator: CPU1 DIMM A2
        Bank Locator: A1_Node0_Channel0_Dimm2
        Type: DDR4
        Type Detail: Synchronous
        Speed: Unknown
        Manufacturer: NO DIMM
        Serial Number: NO DIMM
        Asset Tag: NO DIMM
        Part Number: NO DIMM
        Rank: Unknown
        Configured Memory Speed: Unknown
        Minimum Voltage: Unknown
        Maximum Voltage: Unknown
        Configured Voltage: Unknown

 

Handle 0x002D, DMI type 17, 40 bytes
Memory Device
        Array Handle: 0x0029
        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
        Size: 16 GB
        Form Factor: RIMM
        Set: None
        Locator: CPU1 DIMM B1
        Bank Locator: A1_Node0_Channel1_Dimm1
        Type: DDR4
        Type Detail: Synchronous
        Speed: 2400 MT/s
        Manufacturer: Micron
        Serial Number: 15B363AF
        Asset Tag: CPU1 DIMM B1_AssetTag
        Part Number: 18ASF2G72PDZ-2G3B1 
        Rank: 2
        Configured Memory Speed: 2133 MT/s
        Minimum Voltage: Unknown
        Maximum Voltage: Unknown
        Configured Voltage: Unknown

Handle 0x0035, DMI type 17, 40 bytes
Memory Device
        Array Handle: 0x0031
        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
        Size: 16 GB
        Form Factor: RIMM
        Set: None
        Locator: CPU1 DIMM D1
        Bank Locator: A1_Node0_Channel3_Dimm1
        Type: DDR4
        Type Detail: Synchronous
        Speed: 2133 MT/s
        Manufacturer: Micron
        Serial Number: 1064B491
        Asset Tag: CPU1 DIMM D1_AssetTag
        Part Number: 36ASF2G72PZ-2G1A2  
        Rank: 2
        Configured Memory Speed: 2133 MT/s
        Minimum Voltage: Unknown
        Maximum Voltage: Unknown
        Configured Voltage: Unknown

Handle 0x0033, DMI type 17, 40 bytes
Memory Device
        Array Handle: 0x0031
        Error Information Handle: Not Provided
        Total Width: 72 bits
        Data Width: 64 bits
        Size: 16 GB
        Form Factor: RIMM
        Set: None
        Locator: CPU1 DIMM C1
        Bank Locator: A1_Node0_Channel2_Dimm1
        Type: DDR4
        Type Detail: Synchronous
        Speed: 2133 MT/s
        Manufacturer: Micron
        Serial Number: 10643A5B
        Asset Tag: CPU1 DIMM C1_AssetTag
        Part Number: 36ASF2G72PZ-2G1A2  
        Rank: 2
        Configured Memory Speed: 2133 MT/s
        Minimum Voltage: Unknown
        Maximum Voltage: Unknown
        Configured Voltage: Unknown

 

The marked in green are the banks of memory that are plugged in the server. The

field Speed: and Configured Memory Speed: are fields indicating respectively the Maximum speed on which a plugged-in RAM bank can operate and the the actual Speed the Linux kernel has it configured and uses is at.

It is useful for the admin to usually check the complete number of available RAM slots on a server, this can be done with command like:

root@server:~#  dmidecode –type 17 | grep -i Handle | grep 'DMI'|wc -l
16


As you can see at this specific case 16 Memory slots are avaiable (4 are already occupied and working configured on the machine at 2133 Mhz and 12 are empty and can have installed a memory banks in).


Perhaps the most interesting information for the RAM replacement to be ordered is to know the data communication SPEED on which the Memory is working on the server and interacting with Kernel and Processor to find out.

root@server:~#  dmidecode –type 17 | grep -i "speed"|grep -vi unknown
    Speed: 2400 MT/s
    Configured Memory Speed: 2133 MT/s
    Speed: 2400 MT/s
    Configured Memory Speed: 2133 MT/s
    Speed: 2133 MT/s
    Configured Memory Speed: 2133 MT/s
    Speed: 2133 MT/s
    Configured Memory Speed: 2133 MT/s

 

If you're lazy to remember the exact dmidecode memory type 17 you can use also memory keyword:

root@server:~# dmidecode –type memory | more

For servers that have the lshw command installed, a quick overview of RAM installed and Full slots available for memory placement can be done with:
 

root@server:~#  lshw -short -C memory
H/W path                 Device        Class          Description
=================================================================
/0/0                                   memory         64KiB BIOS
/0/29                                  memory         64GiB System Memory
/0/29/0                                memory         16GiB RIMM DDR4 Synchronous 2400 MHz (0.4 ns)
/0/29/1                                memory         RIMM DDR4 Synchronous [empty]
/0/29/2                                memory         16GiB RIMM DDR4 Synchronous 2400 MHz (0.4 ns)
/0/29/3                                memory         RIMM DDR4 Synchronous [empty]
/0/29/4                                memory         16GiB RIMM DDR4 Synchronous 2133 MHz (0.5 ns)
/0/29/5                                memory         RIMM DDR4 Synchronous [empty]
/0/29/6                                memory         16GiB RIMM DDR4 Synchronous 2133 MHz (0.5 ns)
/0/29/7                                memory         RIMM DDR4 Synchronous [empty]
/0/29/8                                memory         RIMM DDR4 Synchronous [empty]
/0/29/9                                memory         RIMM DDR4 Synchronous [empty]
/0/29/a                                memory         RIMM DDR4 Synchronous [empty]
/0/29/b                                memory         RIMM DDR4 Synchronous [empty]
/0/29/c                                memory         RIMM DDR4 Synchronous [empty]
/0/29/d                                memory         RIMM DDR4 Synchronous [empty]
/0/29/e                                memory         RIMM DDR4 Synchronous [empty]
/0/29/f                                memory         RIMM DDR4 Synchronous [empty]
/0/43                                  memory         768KiB L1 cache
/0/44                                  memory         3MiB L2 cache
/0/45                                  memory         30MiB L3 cache

Now once we know the exact model and RAM Serial and Part number you can google it online and to purchase more of the same RAM Model and Type you need so the installed memory work on the same Megaherzes as the installed ones.
 

How to make 27 inch monitor to work on 2560×1440 with Virtualbox Linux

Wednesday, October 4th, 2023

make-virtualbox-with-linux-work-on-2k-2560x1440-howto

I've bought a new "second hand" refurbished EIZO Flexscan Monitor EV2760 S1 K1 awesome monitor re from Kvant Serviz a company reseller of Second Hand electronics that is located on the territy of Bulgarian Academy of Sciences (BAN / BAS) and was created by BAS people originally for the BAS people and am pretty happy with it for doing my daily job as system administrator, especially as the monitor has been used on very short screen time for only 256 use hours (which is less than a year of full-use time), whether EIZO does guarantee their monitors to be able to serve up to 5 Full years monitor use time.

For those who deals with Graphics such as Designers and people into art working with Computers knows EIZO brand Monitors for quite some time now and it seems as much of those people are using Windows or Macintoshes, these monitors have been mainly created to work optimally with Windows / Mac computers on a higher resolution.
My work PC that is Dell Latitude 5510 with its HDMI cable has been running perfect with The EIZO with Windows 10, however as I'm using a Virtualbox virutal machines with CentOS Linux, the VM does not automatically detected the highest resolution 2K that this monitors supports 2560×1440 at 60 Hz is the best one can use to get more things fit into the screen and hopefully also good for the Eyes, the Ecoview shoulk also be a good idea for the eyes, as the Ecoview by EIZO tries to adjust the monitor brightness to lower levels according to the light in the room to try to minimize the eye strain on the eyes. The Ecoview mode is a little bit I guess like the famous BENQ's monitors Eye care. 
I'm talking about all this Displays specifics as I spend quite a lot of time to learn the very basics about monitors as my old old 24 Inch EIZO Monitor Flexscan model 2436W started to wear off with time and doesn't support HDMI cable input, so I had to use a special. cable connector that modifies the signal from HDMI to DVI (and I'm not sure how this really effects the eyes), plus the DVI quality is said to be a little bit worse than HDMI as far as I read a bit on the topic online.

Well anyways currently I'm a happy owner of the EIZO EV2760 Monitor which has a full set of inputs of:

  • 27" In-Plane Switching (IPS) Panel
  • DisplayPort | HDMI | DVI-D | 3.5mm Audio
  • 2560 x 1440 Native Resolution
  • 1000:1 Typical Contrast Ratio
     

I've tried to make the monitor work with Linux and my first assumption from what I've read was that I have to reinstall the Guess Addition Tools on the Virtualbox with additing the Guest Addition Tools via the Vbox GUI interface:

Devices -> Insert Guest Additions CD Image

virtualbox-resolutions-screenshot

But got an error that the Guest additions tools iso is missing
So eventually resolved it by remounting and reinstalling the guest addition tools with the following set of commands:

[root@localhost test]# yum install perl gcc dkms kernel-devel kernel-headers make bzip2
[root@localhost test]# cd /mnt/cdrom/
[root@localhost cdrom]# ls
AUTORUN.INF  runasroot.sh                       VBoxSolarisAdditions.pkg
autorun.sh   TRANS.TBL                          VBoxWindowsAdditions-amd64.exe
cert         VBoxDarwinAdditions.pkg            VBoxWindowsAdditions.exe
NT3x         VBoxDarwinAdditionsUninstall.tool  VBoxWindowsAdditions-x86.exe
OS2          VBoxLinuxAdditions.run

 


[root@localhost cdrom]# ./VBoxLinuxAdditions.run 

Verifying archive integrity… All good.
Uncompressing VirtualBox 6.1.34 Guest Additions for Linux……..
VirtualBox Guest Additions installer
Removing installed version 6.1.34 of VirtualBox Guest Additions…
Copying additional installer modules …
Installing additional modules …
VirtualBox Guest Additions: Starting.
VirtualBox Guest Additions: Building the VirtualBox Guest Additions kernel
modules.  This may take a while.
VirtualBox Guest Additions: To build modules for other installed kernels, run
VirtualBox Guest Additions:   /sbin/rcvboxadd quicksetup <version>
VirtualBox Guest Additions: or
VirtualBox Guest Additions:   /sbin/rcvboxadd quicksetup all
VirtualBox Guest Additions: Building the modules for kernel
3.10.0-1160.80.1.el7.x86_64.
ERROR: Can't map '//etc/selinux/targeted/policy/policy.31':  Invalid argument

ERROR: Unable to open policy //etc/selinux/targeted/policy/policy.31.
libsemanage.semanage_read_policydb: Error while reading kernel policy from /etc/selinux/targeted/active/policy.kern. (No such file or directory).
OSError: No such file or directory
VirtualBox Guest Additions: Running kernel modules will not be replaced until
the system is restarted

 

 

The solution to that was to reinstal the security policy-target was necessery

[root@localhost test]# yum install selinux-policy-targeted –reinstall


And of course rerun the reinstall of Guest addition tools up to the latest

[root@localhost cdrom]# ./VBoxLinuxAdditions.run 

Unfortunately that doesn't make it resolve it and even shutting down the VM machine and reloading it again with Raised Video Memory for the simulated hardware from settings from 16 MB to 128MB for the VM does not give the option from the Virtualbox interface to set the resolution from
 

View -> Virtual Screen 1 (Resize to 1920×1200)

to any higher than that.

After a bit of googling I found some newer monitors doesn't seem to be seen by xrandr command and few extra commands with xrandr need to be run to make the 2K resolution 2560×1440@60 Herzes work under the Linux virtual machine.

These are the extra xranrd command that make it happen

# xrandr –newmode "2560x1440_60.00" 311.83  2560 2744 3024 3488  1440 1441 1444 1490  -HSync +Vsync
# xrandr –addmode Virtual1 2560x1440_60.00
# xrandr –output Virtual1 –mode "2560x1440_60.00"

As this kind of settings needs to be rerun on next time the Virtual Machine runs it is a good idea to place the commands in a tiny shell script:

[test@localhost ~]$ cat xrandr-set-resolution-to-2560×1440.sh 
#!/bin/bash
xrandr –newmode "2560x1440_60.00" 311.83  2560 2744 3024 3488  1440 1441 1444 1490  -HSync +Vsync
xrandr –addmode Virtual1 2560x1440_60.00
xrandr –output Virtual1 –mode "2560x1440_60.00"


You can Download  the xrandr-set-resolution-to-2560×1440.sh script from here

Once the commands are run, to make it affect the Virtualbox, you can simply put it in FullScreen mode via


View -> Full-Screen Mode (can be teriggered from keyboard by pressing Right CTRL + F) together

[test@localhost ~]$ xrandr –addmode Virtual1 2560x1440_60.00
[test@localhost ~]$ xrandr –output Virtual1 –mode "2560x1440_60.00"
[test@localhost ~]$ xrandr 
Screen 0: minimum 1 x 1, current 2560 x 1440, maximum 8192 x 8192
Virtual1 connected primary 2560×1440+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1920×1200     60.00 +  59.88  
   2560×1600     59.99  
   1920×1440     60.00  
   1856×1392     60.00  
   1792×1344     60.00  
   1600×1200     60.00  
   1680×1050     59.95  
   1400×1050     59.98  
   1280×1024     60.02  
   1440×900      59.89  
   1280×960      60.00  
   1360×768      60.02  
   1280×800      59.81  
   1152×864      75.00  
   1280×768      59.87  
   1024×768      60.00  
   800×600       60.32  
   640×480       59.94  
   2560x1440_60.00  60.00* 
Virtual2 disconnected (normal left inverted right x axis y axis)
Virtual3 disconnected (normal left inverted right x axis y axis)
Virtual4 disconnected (normal left inverted right x axis y axis)
Virtual5 disconnected (normal left inverted right x axis y axis)
Virtual6 disconnected (normal left inverted right x axis y axis)
Virtual7 disconnected (normal left inverted right x axis y axis)
Virtual8 disconnected (normal left inverted right x axis y axis)

Tadadadam ! That's all folks, enjoy having your 27 Inch monitor running at 2560×1440 @ 60 Hz 🙂