Posts Tagged ‘server’

Fix Out of inodes on Postfix Linux Mail Cluster. How to clean up filesystem running out of Inodes, Filesystem inodes on partition is 100% full

Wednesday, August 25th, 2021

Inode_Entry_inode-table-content

Recently we have faced a strange issue with with one of our Clustered Postfix Mail servers (the cluster is with 2 nodes that each has configured Postfix daemon mail servers (running on an OpenVZ virtualized environment).
A heartbeat that checks liveability of clusters and switches nodes in case of one of the two gets broken due to some reason), pretty much a standard SMTP cluster.

So far so good but since the cluster is a kind of abondoned and is pretty much legacy nowadays and used just for some Monitoring emails from different scripts and systems on servers, it was not really checked thoroughfully for years and logically out of sudden the alarming email content sent via the cluster stopped working.

The normal sysadmin job here  was to analyze what is going on with the cluster and fix it ASAP. After some very basic analyzing we catched the problem is caused by a  "inodes full" (100% of available inodes were occupied) problem, e.g. file system run out of inodes on both machines perhaps due to a pengine heartbeat process  bug  leading to producing a high number of .bz2 pengine recovery archive files stored in /var/lib/pengine>

Below are the few steps taken to analyze and fix the problem.
 

1. Finding out about the the system run out of inodes problem


After logging on to system and not finding something immediately is wrong with inodes, all I can see from crm_mon is cluster was broken.
A plenty of emails were left inside the postfix mail queue visible with a standard command

[root@smtp1: ~ ]# postqueue -p

It took me a while to find ot the problem is with inodes because a simple df -h  was showing systems have enough space but still cluster quorum was not complete.
A bit of further investigation led me to a  simple df -i reporting the number of inodes on the local filesystems on both our SMTP1 and SMTP2 got all occupied.

[root@smtp1: ~ ]# df -i
Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/simfs            500000   500000  0   100% /
none                   65536      61   65475    1% /dev

As you can see the number of inodes on the Virual Machine are unfortunately depleted

Next step was to check directories occupying most inodes, as this is the place from where files could be temporary moved to a remote server filesystem or moved to another partition with space on a server locally attached drives.
Below command gives an ordered list with directories locally under the mail root filesystem / and its respective occupied number files / inodes,
the more files under a directory the more inodes are being occupied by the files on the filesystem.

 

run-out-if-inodes-what-is-inode-find-out-which-filesystem-or-directory-eating-up-all-your-system-inodes-linux_inode_diagram.gif
1.1 Getting which directory consumes most of the inodes on the systems

 

[root@smtp1: ~ ]# { find / -xdev -printf '%h\n' | sort | uniq -c | sort -k 1 -n; } 2>/dev/null
….
…..

…….
    586 /usr/lib64/python2.4
    664 /usr/lib64
    671 /usr/share/man/man8
    860 /usr/bin
   1006 /usr/share/man/man1
   1124 /usr/share/man/man3p
   1246 /var/lib/Pegasus/prev_repository_2009-03-10-1236698426.308128000.rpmsave/root#cimv2/classes
   1246 /var/lib/Pegasus/prev_repository_2009-05-18-1242636104.524113000.rpmsave/root#cimv2/classes
   1246 /var/lib/Pegasus/prev_repository_2009-11-06-1257494054.380244000.rpmsave/root#cimv2/classes
   1246 /var/lib/Pegasus/prev_repository_2010-08-04-1280907760.750543000.rpmsave/root#cimv2/classes
   1381 /var/lib/Pegasus/prev_repository_2010-11-15-1289811714.398469000.rpmsave/root#cimv2/classes
   1381 /var/lib/Pegasus/prev_repository_2012-03-19-1332151633.572875000.rpmsave/root#cimv2/classes
   1398 /var/lib/Pegasus/repository/root#cimv2/classes
   1696 /usr/share/man/man3
   400816 /var/lib/pengine

Note, the above command orders the files from bottom to top order and obviosuly the bottleneck directory that is over-eating Filesystem inodes with an exceeding amount of files is
/var/lib/pengine
 

2. Backup old multitude of files just in case of something goes wrong with the cluster after some files are wiped out


The next logical step of course is to check what is going on inside /var/lib/pengine just to find a very ,very large amount of pe-input-*NUMBER*.bz2 files were suddenly produced.

 

[root@smtp1: ~ ]# ls -1 pe-input*.bz2 | wc -l
 400816


The files are produced by the pengine process which is one of the processes that is controlling the heartbeat cluster state, presumably it is done by running process:

[root@smtp1: ~ ]# ps -ef|grep -i pengine
24        5649  5521  0 Aug10 ?        00:00:26 /usr/lib64/heartbeat/pengine


Hence in order to fix the issue, to prevent some inconsistencies in the cluster due to the file deletion,  copied the whole directory to another mounted parition (you can mount it remotely with sshfs for example) or use a local one if you have one:

[root@smtp1: ~ ]# cp -rpf /var/lib/pengine /mnt/attached_storage


and proceeded to clean up some old multitde of files that are older than 2 years of times (720 days):


3. Clean  up /var/lib/pengine files that are older than two years with short loop and find command

 


First I made a list with all the files to be removed in external text file and quickly reviewed it by lessing it like so

[root@smtp1: ~ ]#  cd /var/lib/pengine
[root@smtp1: ~ ]# find . -type f -mtime +720|grep -v pe-error.last | grep -v pe-input.last |grep -v pe-warn.last -fprint /home/myuser/pengine_older_than_720days.txt
[root@smtp1: ~ ]# less /home/myuser/pengine_older_than_720days.txt


Once reviewing commands I've used below command to delete the files you can run below command do delete all older than 2 years that are different from pe-error.last / pe-input.last / pre-warn.last which might be needed for proper cluster operation.

[root@smtp1: ~ ]#  for i in $(find . -type f -mtime +720 -exec echo '{}' \;|grep -v pe-error.last | grep -v pe-input.last |grep -v pe-warn.last); do echo $i; done


Another approach to the situation is to simply review all the files inside /var/lib/pengine and delete files based on year of creation, for example to delete all files in /var/lib/pengine from 2010, you can run something like:
 

[root@smtp1: ~ ]# for i in $(ls -al|grep -i ' 2010 ' | awk '{ print $9 }' |grep -v 'pe-warn.last'); do rm -f $i; done


4. Monitor real time inodes freeing

While doing the clerance of old unnecessery pengine heartbeat archives you can open another ssh console to the server and view how the inodes gets freed up with a command like:

 

# check if inodes is not being rapidly decreased

[root@csmtp1: ~ ]# watch 'df -i'


5. Restart basic Linux services producing pid files and logs etc. to make then workable (some services might not be notified the inodes on the Hard drive are freed up)

Because the hard drive on the system was full some services started to misbehaving and /var/log logging was impacted so I had to also restart them in our case this is the heartbeat itself
that  checks clusters nodes availability as well as the logging daemon service rsyslog

 

# restart rsyslog and heartbeat services
[root@csmtp1: ~ ]# /etc/init.d/heartbeat restart
[root@csmtp1: ~ ]# /etc/init.d/rsyslog restart

The systems had been a data integrity legacy service samhain so I had to restart this service as well to reforce the /var/log/samhain log file to again continusly start writting data to HDD.

# Restart samhain service init script 
[root@csmtp1: ~ ]# /etc/init.d/samhain restart


6. Check up enough inodes are freed up with df

[root@smtp1 log]# df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/simfs 500000 410531 19469 91% /
none 65536 61 65475 1% /dev


I had to repeat the same process on the second Postfix cluster node smtp2, and after all the steps like below check the status of smtp2 node and the postfix queue, following same procedure made the second smtp2 cluster member as expected 🙂

 

7. Check the cluster node quorum is complete, e.g. postfix cluster is operating normally

 

# Test if email cluster is ok with pacemaker resource cluster manager – lt-crm_mon
 

[root@csmtp1: ~ ]# crm_mon -1
============
Last updated: Tue Aug 10 18:10:48 2021
Stack: Heartbeat
Current DC: smtp2.fqdn.com (bfb3d029-89a8-41f6-a9f0-52d377cacd83) – partition with quorum
Version: 1.0.12-unknown
2 Nodes configured, unknown expected votes
4 Resources configured.
============

Online: [ smtp2.fqdn.com smtp1.fqdn.com ]

failover-ip (ocf::heartbeat:IPaddr2): Started csmtp1.ikossvan.de
Clone Set: postfix_clone
Started: [ smtp2.fqdn.com smtp1fqdn.com ]
Clone Set: pingd_clone
Started: [ smtp2.fqdn.com smtp1.fqdn.com ]
Clone Set: mailto_clone
Started: [ smtp2.fqdn.com smtp1.fqdn.com ]

 

8.  Force resend a few hundred thousands of emails left in the email queue


After some inodes gets freed up due to the file deletion, i've reforced a couple of times the queued mail servers to be immediately resent to remote mail destinations with cmd:

 

# force emails in queue to be resend with postfix

[root@smtp1: ~ ]# sendmail -q


– It was useful to watch in real time how the queued emails are quickly decreased (queued mails are successfully sent to destination addresses) with:

 

# Monitor  the decereasing size of the email queue
[root@smtp1: ~ ]# watch 'postqueue -p|grep -i '@'|wc -l'

How to configure bond0 bonding and network bridging for KVM Virtual machines on Redhat / CentOS / Fedora Linux

Tuesday, February 16th, 2021

configure-bond0-bonding-channel-with-bridges-on-hypervisor-host-for-guest-KVM-virtual-machines-howto-sample-Hypervisor-Virtual-machines-pic
 1. Intro to Redhat RPM based distro /etc/sysconfig/network-scripts/* config vars shortly explained

On RPM based Linux distributions configuring network has a very specific structure. As a sysadmin just recently I had a task to configure Networking on 2 Machines to be used as Hypervisors so the servers could communicate normally to other Networks via some different intelligent switches that are connected to each of the interfaces of the server. The idea is the 2 redhat 8.3 machines to be used as  Hypervisor (HV) and each of the 2 HVs to each be hosting 2 Virtual guest Machines with preinstalled another set of Redhat 8.3 Ootpa. I've recently blogged on how to automate a bit installing the KVM Virtual machines with using predefined kickstart.cfg file.

The next step after install was setting up the network. Redhat has a very specific network configuration well known under /etc/sysconfig/network-scripts/ifcfg-eno*# or if you have configured the Redhats to fix the changing LAN card naming ens, eno, em1 to legacy eth0, eth1, eth2 on CentOS Linux – e.g. to be named as /etc/sysconfig/network-scripts/{ifcfg-eth0,1,2,3}.

The first step to configure the network from that point is to come up with some network infrastrcture that will be ready on the HV nodes server-node1 server-node2 for the Virtual Machines to be used by server-vm1, server-vm2.

Thus for the sake of myself and some others I decide to give here the most important recognized variables that can be placed inside each of the ifcfg-eth0,ifcfg-eth1,ifcfg-eth2 …

A standard ifcfg-eth0 confing would look something this:
 

[root@redhat1 :~ ]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
TYPE=Ethernet
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV4_FAILURE_FATAL=no
NAME=eth0
UUID=…
ONBOOT=yes
HWADDR=0e:a4:1a:b6:fc:86
IPADDR0=10.31.24.10
PREFIX0=23
GATEWAY0=10.31.24.1
DNS1=192.168.50.3
DNS2=10.215.105.3
DOMAIN=example.com
IPV6_PEERDNS=yes
IPV6_PEERROUTES=yes


Lets say few words to each of the variables to make it more clear to people who never configured Newtork on redhat without the help of some of the console ncurses graphical like tools such as nmtui or want to completely stop the Network-Manager to manage the network and thus cannot take the advantage of using nmcli (a command-line tool for controlling NetworkManager).

Here is a short description of each of above configuration parameters:

TYPE=device_type: The type of network interface device
BOOTPROTO=protocol: Where protocol is one of the following:

  • none: No boot-time protocol is used.
  • bootp: Use BOOTP (bootstrap protocol).
  • dhcp: Use DHCP (Dynamic Host Configuration Protocol).
  • static: if configuring static IP

EFROUTE|IPV6_DEFROUTE=answer

  • yes: This interface is set as the default route for IPv4|IPv6 traffic.
  • no: This interface is not set as the default route.

Usually most people still don't use IPV6 so better to disable that

IPV6INIT=answer: Where answer is one of the following:

  • yes: Enable IPv6 on this interface. If IPV6INIT=yes, the following parameters could also be set in this file:

IPV6ADDR=IPv6 address

IPV6_DEFAULTGW=The default route through the specified gateway

  • no: Disable IPv6 on this interface.

IPV4_FAILURE_FATAL|IPV6_FAILURE_FATAL=answer: Where answer is one of the following:

  • yes: This interface is disabled if IPv4 or IPv6 configuration fails.
  • no: This interface is not disabled if configuration fails.

ONBOOT=answer: Where answer is one of the following:

  • yes: This interface is activated at boot time.
  • no: This interface is not activated at boot time.

HWADDR=MAC-address: The hardware address of the Ethernet device
IPADDRN=address: The IPv4 address assigned to the interface
PREFIXN=N: Length of the IPv4 netmask value
GATEWAYN=address: The IPv4 gateway address assigned to the interface. Because an interface can be associated with several combinations of IP address, network mask prefix length, and gateway address, these are numbered starting from 0.
DNSN=address: The address of the Domain Name Servers (DNS)
DOMAIN=DNS_search_domain: The DNS search domain (this is the search Domain-name.com you usually find in /etc/resolv.conf)

Other interesting file that affects how routing is handled on a Redhat Linux is

/etc/sysconfig/network

[root@redhat1 :~ ]# cat /etc/sysconfig/network
# Created by anaconda
GATEWAY=10.215.105.

Having this gateway defined does add a default gateway

This file specifies global network settings. For example, you can specify the default gateway, if you want to apply some network settings such as routings, Alias IPs etc, that will be valid for all configured and active configuration red by systemctl start network scripts or the (the network-manager if such is used), just place it in that file.

Other files of intesresting to control how resolving is being handled on the server worthy to check are 

/etc/nsswitch.conf

and

/etc/hosts

If you want to set a preference of /etc/hosts being red before /etc/resolv.conf and DNS resolving for example you need to have inside it, below is default behavior of it.
 

root@redhat1 :~ ]#   grep -i hosts /etc/nsswitch.conf
#     hosts: files dns
#     hosts: files dns  # from user file
# Valid databases are: aliases, ethers, group, gshadow, hosts,
hosts:      files dns myhostname

As you can see the default order is to read first files (meaning /etc/hosts) and then the dns (/etc/resolv.conf)
hosts: files dns

Now with this short intro description on basic values accepted by Redhat's /etc/sysconfig/network-scripts/ifcfg* prepared configurations.


I will give a practical example of configuring a bond0 interface with 2 members which were prepared based on Redhat's Official documentation found in above URLs:

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/configuring_and_managing_networking/configuring-network-bonding_configuring-and-managing-networking
 

# Bonding on RHEL 7 documentation
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/networking_guide/sec-network_bonding_using_the_command_line_interface

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/networking_guide/sec-verifying_network_configuration_bonding_for_redundancy

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/deployment_guide/s2-networkscripts-interfaces_network-bridge

# Network Bridge with Bond documentation
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/deployment_guide/sec-Configuring_a_VLAN_over_a_Bond

https://docs.fedoraproject.org/en-US/Fedora/24/html/Networking_Guide/sec-Network_Bridge_with_Bond.html


2. Configuring a single bond connection on eth0 / eth2 and setting 3 bridge interfaces bond -> br0, br1 -> eth1, br2 -> eth2

The task on my machines was to set up from 4 lan cards one bonded interface as active-backup type of bond with bonded lines on eth0, eth2 and 3 other 2 eth1, eth2 which will be used for private communication network that is connected via a special dedicated Switches and Separate VLAN 50, 51 over a tagged dedicated gigabit ports.

As said the 2 Servers had each 4 Broadcom Network CARD interfaces each 2 of which are paired (into a single card) and 2 of which are a solid Broadcom NetXtreme Dual Port 10GbE SFP+ and Dell Broadcom 5720 Dual Port 1Gigabit Network​.

2-ports-broadcom-netxtreme-dual-port-10GBe-spf-plus

On each of server-node1 and server-node2 we had 4 Ethernet Adapters properly detected on the Redhat

root@redhat1 :~ ]# lspci |grep -i net
01:00.0 Ethernet controller: Broadcom Inc. and subsidiaries NetXtreme BCM5720 2-port Gigabit Ethernet PCIe
01:00.1 Ethernet controller: Broadcom Inc. and subsidiaries NetXtreme BCM5720 2-port Gigabit Ethernet PCIe
19:00.0 Ethernet controller: Broadcom Inc. and subsidiaries BCM57412 NetXtreme-E 10Gb RDMA Ethernet Controller (rev 01)
19:00.1 Ethernet controller: Broadcom Inc. and subsidiaries BCM57412 NetXtreme-E 10Gb RDMA Ethernet Controller (rev 01)


I've already configured as prerogative net.ifnames=0 to /etc/grub2/boot.cfg and Network-Manager service disabled on the host (hence to not use Network Manager you'll see in below configuration NM_CONTROLLED="no" is telling the Redhat servers is not to be trying NetworkManager for more on that check my previous article Disable NetworkManager automatic Ethernet Interface Management on Redhat Linux , CentOS 6 / 7 / 8.

3. Types of Network Bonding

mode=0 (balance-rr)

This mode is based on Round-robin policy and it is the default mode. This mode offers fault tolerance and load balancing features. It transmits the packets in Round robin fashion that is from the first available slave through the last.

mode-1 (active-backup)

This mode is based on Active-backup policy. Only one slave is active in this band, and another one will act only when the other fails. The MAC address of this bond is available only on the network adapter part to avoid confusing the switch. This mode also provides fault tolerance.

mode=2 (balance-xor)

This mode sets an XOR (exclusive or) mode that is the source MAC address is XOR’d with destination MAC address for providing load balancing and fault tolerance. Each destination MAC address the same slave is selected.

mode=3 (broadcast)

This method is based on broadcast policy that is it transmitted everything on all slave interfaces. It provides fault tolerance. This can be used only for specific purposes.

mode=4 (802.3ad)

This mode is known as a Dynamic Link Aggregation mode that has it created aggregation groups having same speed. It requires a switch that supports IEEE 802.3ad dynamic link. The slave selection for outgoing traffic is done based on a transmit hashing method. This may be changed from the XOR method via the xmit_hash_policy option.

mode=5 (balance-tlb)

This mode is called Adaptive transmit load balancing. The outgoing traffic is distributed based on the current load on each slave and the incoming traffic is received by the current slave. If the incoming traffic fails, the failed receiving slave is replaced by the MAC address of another slave. This mode does not require any special switch support.

mode=6 (balance-alb)

This mode is called adaptive load balancing. This mode does not require any special switch support.

Lets create the necessery configuration for the bond and bridges

[root@redhat1 :~ ]# cat ifcfg-bond0
DEVICE=bond0
NAME=bond0
TYPE=Bond
BONDING_MASTER=yes
#IPADDR=10.50.21.16
#PREFIX=26
#GATEWAY=10.50.0.1
#DNS1=172.20.88.2
ONBOOT=yes
BOOTPROTO=none
BONDING_OPTS="mode=1 miimon=100 primary=eth0"
NM_CONTROLLED="no"
BRIDGE=br0


[root@redhat1 :~ ]# cat ifcfg-bond0.10
DEVICE=bond0.10
BOOTPROTO=none
ONPARENT=yes
#IPADDR=10.50.21.17
#NETMASK=255.255.255.0
VLAN=yes

[root@redhat1 :~ ]# cat ifcfg-br0
STP=yes
BRIDGING_OPTS=priority=32768
TYPE=Bridge
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
#IPV6INIT=yes
#IPV6_AUTOCONF=yes
#IPV6_DEFROUTE=yes
#IPV6_FAILURE_FATAL=no
#IPV6_ADDR_GEN_MODE=stable-privacy
IPV6_AUTOCONF=no
IPV6_DEFROUTE=no
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=br0
UUID=4451286d-e40c-4d8c-915f-7fc12a16d595
DEVICE=br0
ONBOOT=yes
IPADDR=10.50.50.16
PREFIX=26
GATEWAY=10.50.0.1
DNS1=172.20.0.2
NM_CONTROLLED=no

[root@redhat1 :~ ]# cat ifcfg-br1
STP=yes
BRIDGING_OPTS=priority=32768
TYPE=Bridge
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=no
IPV4_FAILURE_FATAL=no
#IPV6INIT=yes
#IPV6_AUTOCONF=yes
#IPV6_DEFROUTE=yes
#IPV6_FAILURE_FATAL=no
#IPV6_ADDR_GEN_MODE=stable-privacy
IPV6INIT=no
IPV6_AUTOCONF=no
IPV6_DEFROUTE=no
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=br1
UUID=40360c3c-47f5-44ac-bbeb-77f203390d29
DEVICE=br1
ONBOOT=yes
##IPADDR=10.50.51.241
PREFIX=28
##GATEWAY=10.50.0.1
##DNS1=172.20.0.2
NM_CONTROLLED=no

[root@redhat1 :~ ]# cat ifcfg-br2
STP=yes
BRIDGING_OPTS=priority=32768
TYPE=Bridge
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=no
IPV4_FAILURE_FATAL=no
#IPV6INIT=yes
#IPV6_AUTOCONF=yes
#IPV6_DEFROUTE=yes
#IPV6_FAILURE_FATAL=no
#IPV6_ADDR_GEN_MODE=stable-privacy
IPV6INIT=no
IPV6_AUTOCONF=no
IPV6_DEFROUTE=no
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=br2
UUID=fbd5c257-2f66-4f2b-9372-881b783276e0
DEVICE=br2
ONBOOT=yes
##IPADDR=10.50.51.243
PREFIX=28
##GATEWAY=10.50.0.1
##DNS1=172.20.10.1
NM_CONTROLLED=no
NM_CONTROLLED=no
BRIDGE=br0

[root@redhat1 :~ ]# cat ifcfg-eth0
TYPE=Ethernet
NAME=bond0-slaveeth0
BOOTPROTO=none
#UUID=61065574-2a9d-4f16-b16e-00f495e2ee2b
DEVICE=eth0
ONBOOT=yes
MASTER=bond0
SLAVE=yes
NM_CONTROLLED=no

[root@redhat1 :~ ]# cat ifcfg-eth1
TYPE=Ethernet
NAME=eth1
UUID=b4c359ae-7a13-436b-a904-beafb4edee94
DEVICE=eth1
ONBOOT=yes
BRIDGE=br1
NM_CONTROLLED=no

[root@redhat1 :~ ]#  cat ifcfg-eth2
TYPE=Ethernet
NAME=bond0-slaveeth2
BOOTPROTO=none
#UUID=821d711d-47b9-490a-afe7-190811578ef7
DEVICE=eth2
ONBOOT=yes
MASTER=bond0
SLAVE=yes
NM_CONTROLLED=no

[root@redhat1 :~ ]#  cat ifcfg-eth3
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
#BOOTPROTO=dhcp
BOOTPROTO=none
DEFROUTE=no
IPV4_FAILURE_FATAL=no
#IPV6INIT=yes
#IPV6_AUTOCONF=yes
#IPV6_DEFROUTE=yes
#IPV6_FAILURE_FATAL=no
#IPV6_ADDR_GEN_MODE=stable-privacy
IPV6INIT=no
IPV6_AUTOCONF=no
IPV6_DEFROUTE=no
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
BRIDGE=br2
NAME=eth3
UUID=61065574-2a9d-4f16-b16e-00f495e2ee2b
DEVICE=eth3
ONBOOT=yes
NM_CONTROLLED=no

[root@redhat2 :~ ]# cat ifcfg-bond0
DEVICE=bond0
NAME=bond0
TYPE=Bond
BONDING_MASTER=yes
#IPADDR=10.50.21.16
#PREFIX=26
#GATEWAY=10.50.21.1
#DNS1=172.20.88.2
ONBOOT=yes
BOOTPROTO=none
BONDING_OPTS="mode=1 miimon=100 primary=eth0"
NM_CONTROLLED="no"
BRIDGE=br0

# cat ifcfg-bond0.10
DEVICE=bond0.10
BOOTPROTO=none
ONPARENT=yes
#IPADDR=10.50.21.17
#NETMASK=255.255.255.0
VLAN=yes
NM_CONTROLLED=no
BRIDGE=br0

[root@redhat2 :~ ]# cat ifcfg-br0
STP=yes
BRIDGING_OPTS=priority=32768
TYPE=Bridge
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
#IPV6INIT=yes
#IPV6_AUTOCONF=yes
#IPV6_DEFROUTE=yes
#IPV6_FAILURE_FATAL=no
#IPV6_ADDR_GEN_MODE=stable-privacy
IPV6_AUTOCONF=no
IPV6_DEFROUTE=no
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=br0
#UUID=f87e55a8-0fb4-4197-8ccc-0d8a671f30d0
UUID=4451286d-e40c-4d8c-915f-7fc12a16d595
DEVICE=br0
ONBOOT=yes
IPADDR=10.50.21.17
PREFIX=26
GATEWAY=10.50.21.1
DNS1=172.20.88.2
NM_CONTROLLED=no

[root@redhat2 :~ ]#  cat ifcfg-br1
STP=yes
BRIDGING_OPTS=priority=32768
TYPE=Bridge
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=no
IPV4_FAILURE_FATAL=no
#IPV6INIT=no
#IPV6_AUTOCONF=no
#IPV6_DEFROUTE=no
#IPV6_FAILURE_FATAL=no
#IPV6_ADDR_GEN_MODE=stable-privacy
IPV6INIT=no
IPV6_AUTOCONF=no
IPV6_DEFROUTE=no
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=br1
UUID=40360c3c-47f5-44ac-bbeb-77f203390d29
DEVICE=br1
ONBOOT=yes
##IPADDR=10.50.21.242
PREFIX=28
##GATEWAY=10.50.21.1
##DNS1=172.20.88.2
NM_CONTROLLED=no

[root@redhat2 :~ ]# cat ifcfg-br2
STP=yes
BRIDGING_OPTS=priority=32768
TYPE=Bridge
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=no
IPV4_FAILURE_FATAL=no
#IPV6INIT=no
#IPV6_AUTOCONF=no
#IPV6_DEFROUTE=no
#IPV6_FAILURE_FATAL=no
#IPV6_ADDR_GEN_MODE=stable-privacy
IPV6INIT=no
IPV6_AUTOCONF=no
IPV6_DEFROUTE=no
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=br2
UUID=fbd5c257-2f66-4f2b-9372-881b783276e0
DEVICE=br2
ONBOOT=yes
##IPADDR=10.50.21.244
PREFIX=28
##GATEWAY=10.50.21.1
##DNS1=172.20.88.2
NM_CONTROLLED=no

[root@redhat2 :~ ]# cat ifcfg-eth0
TYPE=Ethernet
NAME=bond0-slaveeth0
BOOTPROTO=none
#UUID=ee950c07-7eb2-463b-be6e-f97e7ad9d476
DEVICE=eth0
ONBOOT=yes
MASTER=bond0
SLAVE=yes
NM_CONTROLLED=no

[root@redhat2 :~ ]# cat ifcfg-eth1
TYPE=Ethernet
NAME=eth1
UUID=ffec8039-58f0-494a-b335-7a423207c7e6
DEVICE=eth1
ONBOOT=yes
BRIDGE=br1
NM_CONTROLLED=no

[root@redhat2 :~ ]# cat ifcfg-eth2
TYPE=Ethernet
NAME=bond0-slaveeth2
BOOTPROTO=none
#UUID=2c097475-4bef-47c3-b241-f5e7f02b3395
DEVICE=eth2
ONBOOT=yes
MASTER=bond0
SLAVE=yes
NM_CONTROLLED=no


Notice that the bond0 configuration does not have an IP assigned this is done on purpose as we're using the interface channel bonding together with attached bridge for the VM. Usual bonding on a normal physical hardware hosts where no virtualization use is planned is perhaps a better choice. If you however try to set up an IP address in that specific configuration shown here and you try to reboot the machine, you will end up with inacessible machine over the network like I did and you will need to resolve configuration via some kind of ILO / IDRAC interface.

4. Generating UUID for ethernet devices bridges and bonds

One thing to note is the command uuidgen you might need that to generate UID identificators to fit in the new network config files.

Example:
 

[root@redhat2 :~ ]#uuidgen br2
e7995e15-7f23-4ea2-80d6-411add78d703
[root@redhat2 :~ ]# uuidgen br1
05e0c339-5998-414b-b720-7adf91a90103
[root@redhat2 :~ ]# uuidgen br0
e6d7ff74-4c15-4d93-a150-ff01b7ced5fb


5. How to make KVM Virtual Machines see configured Network bridges (modify VM XML)

To make the Virtual machines installed see the bridges I had to

[root@redhat1 :~ ]#virsh edit VM_name1
[root@redhat1 :~ ]#virsh edit VM_name2

[root@redhat2 :~ ]#virsh edit VM_name1
[root@redhat2 :~ ]#virsh edit VM_name2

Find the interface network configuration and change it to something like:

    <interface type='bridge'>
      <mac address='22:53:00:56:5d:ac'/>
      <source bridge='br0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>
    <interface type='bridge'>
      <mac address='22:53:00:2a:5f:01'/>
      <source bridge='br1'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x07' slot='0x00' function='0x0'/>
    </interface>
    <interface type='bridge'>
      <mac address='22:34:00:4a:1b:6c'/>
      <source bridge='br2'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x08' slot='0x00' function='0x0'/>
    </interface>


6. Testing the bond  is up and works fine

# ip addr show bond0
The result is the following:

 

4: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 52:54:00:cb:25:82 brd ff:ff:ff:ff:ff:ff


The bond should be visible in the normal network interfaces with ip address show or /sbin/ifconfig

 

# cat /proc/net/bonding/bond0
Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011)

Bonding Mode: fault-tolerance (active-backup)
Primary Slave: None
Currently Active Slave: eth0
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 0
Down Delay (ms): 0

Slave Interface: eth2
MII Status: up
Speed: 10000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 00:0c:29:ab:2a:fa
Slave queue ID: 0

 

According to the output eth0 is the active slave.

The active slaves device files (eth0 in this case) is found in virtual file system /sys/

# find /sys -name *eth0
/sys/devices/pci0000:00/0000:00:15.0/0000:03:00.0/net/eth0
/sys/devices/virtual/net/bond0/lower_eth0
/sys/class/net/eth0


You can remove a bond member say eth0 by 

 

 cd to the pci* directory
Example: /sys/devices/pci000:00/000:00:15.0

 

# echo 1 > remove


At this point the eth0 device directory structure that was previously located under /sys/devices/pci000:00/000:00:15.0 is no longer there.  It was removed and the device no longer exists as seen by the OS.

You can verify this is the case with a simple ifconfig which will no longer list the eth0 device.
You can also repeat the cat /proc/net/bonding/bond0 command from Step 1 to see that eth0 is no longer listed as active or available.
You can also see the change in the messages file.  It might look something like this:

2021-02-12T14:13:23.363414-06:00 redhat1  device eth0: device has been deleted
2021-02-12T14:13:23.368745-06:00 redhat1 kernel: [81594.846099] bonding: bond0: releasing active interface eth0
2021-02-12T14:13:23.368763-06:00 redhat1 kernel: [81594.846105] bonding: bond0: Warning: the permanent HWaddr of eth0 – 00:0c:29:ab:2a:f0 – is still in use by bond0. Set the HWaddr of eth0 to a different address to avoid conflicts.
2021-02-12T14:13:23.368765-06:00 redhat1 kernel: [81594.846132] bonding: bond0: making interface eth1 the new active one.

 

Another way to test the bonding is correctly switching between LAN cards on case of ethernet hardware failure is to bring down one of the 2 or more bonded interfaces, lets say you want to switch from active-backup from eth1 to eth2, do:
 

# ip link set dev eth0 down


That concludes the test for fail over on active slave failure.

7. Bringing bond updown (rescan) bond with no need for server reboot

You know bonding is a tedious stuff that sometimes breaks up badly so only way to fix the broken bond seems to be a init 6 (reboot) cmd but no actually that is not so.

You can also get the deleted device back with a simple pci rescan command:

# echo 1 > /sys/bus/pci/rescan


The eth0 interface should now be back
You can see that it is back with an ifconfig command, and you can verify that the bond sees it with this command:

# cat /proc/net/bonding/bond0


That concludes the test of the bond code seeing the device when it comes back again.

The same steps can be repeated only this time using the eth1 device and file structure to fail the active slave in the bond back over to eth0.

8. Testing the bond with ifenslave command (ifenslave command examples)

Below is a set of useful information to test the bonding works as expected with ifenslave command  comes from "iputils-20071127" package

– To show information of all the inerfaces

                  # ifenslave -a
                  # ifenslave –all-interfaces 

 

– To change the active slave

                  # ifenslave -c bond0 eth1
                  # ifenslave –change-active bond0 eth1 

 

– To remove the slave interface from the bonding device

                  # ifenslave -d eth1
                  # ifenslave –detach bond0 eth1 

 

– To show master interface info

                  # ifenslave bond0 

 

– To set the bond device down and automatically release all the slaves

                  # ifenslave bond1 down 

– To get the usage info

                  # ifenslave -u
                  # ifenslave –usage 

– To set to verbose mode

                  # ifenslave -v
                  # ifenslave –verbose 

9. Testing the bridge works fine

Historically over the years all kind of bridges are being handled with the brctl part of bridge-utils .deb / .rpm installable package.

The classical way to check a bridge is working is to do

# brctl show
# brctl show br0; brctl show br1; brctl show br2

# brctl showmacs br0
 

etc.

Unfortunately with redhat 8 this command is no longer available so to get information about configured bridges you need to use instead:

 

# bridge link show
3:eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state forwarding priority 32 cost 100
4:eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master bridge0 state listening priority 32 cost 100


10. Troubleshooting network connectivity issues on bond bridges and LAN cards

Testing the bond connection and bridges can route proper traffic sometimes is a real hassle so here comes at help the good old tcpdump

If you end up with issues with some of the ethernet interfaces between HV1 and HV2 to be unable to talk to each other and you have some suspiciousness that some colleague from the network team has messed up a copper (UTP) cable or there is a connectivity fiber optics issues. To check the VLAN tagged traffic headers on the switch you can listen to each and every bond0 and br0, br1, br2 eth0, eth1, eth2, eth3 configured on the server like so:

# tcpdump -i bond0 -nn -e vlan


Some further investigation on where does a normal ICMP traffic flows once everything is setup is a normal thing to do, hence just try to route a normal ping via the different server interfaces:

# ping -I bond0 DSTADDR

# ping -i eth0 DSTADDR

# ping -i eth1 DSTADDR

# ping -i eth2 DSTADDR


After conducting the ping do the normal for network testing big ICMP packages (64k) ping to make sure there are no packet losses etc., e.g:

# ping -I eth3 -s 64536  DSTADDR


If for 10 – 20 seconds the ping does not return package losses then you should be good.

How to restart Microsoft IIS with command via Windows command line

Friday, August 19th, 2011

I'm tuning a Windows 2003 for better performance and securing it against DoS of service attacks. After applying all the changes I needed to restart the WebServer for the new configurations to take effect.
As I'm not a GUI kind of guy I found it handy there is a fast command to restart the Microsoft Internet Information Server. The command to restart IIS is:

c:> iisreset

Check server Internet connectivity Speedtest from Linux terminal CLI

Friday, August 7th, 2020

check-server-console-speedtest

If you are a system administrator of a dedicated server and you have no access to Xserver Graphical GNOME / KDE etc. environment and you wonder how you can track the bandwidth connectivity speed of remote system to the internet and you happen to have a modern Linux distribution, here is few ways to do a speedtest.
 

1. Use speedtest-cli command line tool to test connectivity

 


speedtest-cli is a tiny tool written in python, to use it hence you need to have python installed on the server.
It is available both for Redhat Linux distros and Debians / Ubuntus etc. in the list of standard installable packages.

a) Install speedtest-cli on Fedora / CentOS / RHEL
 

On CentOS / RHEL / Scientific Linux lower than ver 8:

 

 

$ sudo yum install python

On CentOS 8 / RHEL 8 user type the following command to install Python 3 or 2:

 

 

$sudo yum install python3
$ sudo yum install python2

 

 

 


On Fedora Linux version 22+

 

 

$ sudo dnf install python
$ sudo dnf install pytho3

 


Once python is at place download speedtest.py or in case if link is not reachable download mirrored version of speedtest.py on www.pc-freak.net here
 

 

 

$ wget -O speedtest-cli https://raw.githubusercontent.com/sivel/speedtest-cli/master/speedtest.py
$ chmod +x speedtest-cli

 


Then it is time to run script speedtest-screenshot-linux-terminal-console-cli-cmd
To test enabled Bandwidth on the server

 

 

$ python speedtest-cli


b) Install speedtest-cli on Debian

On Latest Debian 10 Buster speedtest is available out of the box in regular .deb repositories, so fetch it with apt
 

 

# apt install –yes speedtest-cli

 


You can give now speedtest-cli a try with –bytes arguments to get speed values in bytes instead of bits or if you want to generate an image with test results in picture just like it will appear if you use speedtest.net inside a gui browser, use the –share option

speedtest-screenshot-linux-terminal-console-cli-cmd-options

 

 

 

2. Getting connectivity results of all defined speedtest test City Locations


Speedtest has a list of servers through which a Upload and Download speed is tested, to run speedtest-cli to test with each and every server and get a better picture on what kind of connectivity to expect from your server towards the closest region capital cities, fetch speedtest-servers.php list and use a small shell loop below is how:

 

 

 

 

 

root@pcfreak:~#  wget http://www.speedtest.net/speedtest-servers.php
–2020-08-07 16:31:34–  http://www.speedtest.net/speedtest-servers.php
Преобразувам www.speedtest.net (www.speedtest.net)… 151.101.2.219, 151.101.66.219, 151.101.130.219, …
Connecting to www.speedtest.net (www.speedtest.net)|151.101.2.219|:80… успешно свързване.
HTTP изпратено искане, чакам отговор… 301 Moved Permanently
Адрес: https://www.speedtest.net/speedtest-servers.php [следва]
–2020-08-07 16:31:34–  https://www.speedtest.net/speedtest-servers.php
Connecting to www.speedtest.net (www.speedtest.net)|151.101.2.219|:443… успешно свързване.
HTTP изпратено искане, чакам отговор… 307 Temporary Redirect
Адрес: https://c.speedtest.net/speedtest-servers-static.php [следва]
–2020-08-07 16:31:35–  https://c.speedtest.net/speedtest-servers-static.php
Преобразувам c.speedtest.net (c.speedtest.net)… 151.101.242.219
Connecting to c.speedtest.net (c.speedtest.net)|151.101.242.219|:443… успешно свързване.
HTTP изпратено искане, чакам отговор… 200 OK
Дължина: 211695 (207K) [text/xml]
Saving to: ‘speedtest-servers.php’
speedtest-servers.php                  100%[==========================================================================>] 206,73K  –.-KB/s    in 0,1s
2020-08-07 16:31:35 (1,75 MB/s) – ‘speedtest-servers.php’ saved [211695/211695]

Once file is there with below loop we extract all file defined servers id="" 's 
 

root@pcfreak:~# for i in $(cat speedtest-servers.php | egrep -Eo 'id="[0-9]{4}"' |sed -e 's#id="##' -e 's#"##g'); do speedtest-cli  –server $i; done
Retrieving speedtest.net configuration…
Testing from Vivacom (83.228.93.76)…
Retrieving speedtest.net server list…
Retrieving information for the selected server…
Hosted by Telecoms Ltd. (Varna) [38.88 km]: 25.947 ms
Testing download speed……………………………………………………………………..
Download: 57.71 Mbit/s
Testing upload speed…………………………………………………………………………………………
Upload: 93.85 Mbit/s
Retrieving speedtest.net configuration…
Testing from Vivacom (83.228.93.76)…
Retrieving speedtest.net server list…
Retrieving information for the selected server…
Hosted by GMB Computers (Constanta) [94.03 km]: 80.247 ms
Testing download speed……………………………………………………………………..
Download: 35.86 Mbit/s
Testing upload speed…………………………………………………………………………………………
Upload: 80.15 Mbit/s
Retrieving speedtest.net configuration…
Testing from Vivacom (83.228.93.76)…

…..

 


etc.

For better readability you might want to add the ouput to a file or even put it to run periodically on a cron if you have some suspcion that your server Internet dedicated lines dies out to some general locations sometimes.
 

3. Testing UPlink speed with Download some big file from source location


In the past a classical way to test the bandwidth connectivity of your Internet Service Provider was to fetch some big file, Linux guys should remember it was almost a standard to roll a download of Linux kernel source .tar file with some test browser as elinks / lynx / w3c.
speedtest-screenshot-kernel-org-shot1 speedtest-screenshot-kernel-org-shot2
or if those are not at hand test connectivity on remote free shell servers whatever file downloader as wget or curl was used.
Analogical method is still possible, for example to use wget to get an idea about bandwidtch connectivity, let it roll below 500 mb from speedtest.wdc01.softlayer.com to /dev/null few times:

 

$ wget –output-document=/dev/null http://speedtest.wdc01.softlayer.com/downloads/test500.zip

$ wget –output-document=/dev/null http://speedtest.wdc01.softlayer.com/downloads/test500.zip

$ wget –output-document=/dev/null http://speedtest.wdc01.softlayer.com/downloads/test500.zip

 

# wget -O /dev/null –progress=dot:mega http://cachefly.cachefly.net/10mb.test ; date
–2020-08-07 13:56:49–  http://cachefly.cachefly.net/10mb.test
Resolving cachefly.cachefly.net (cachefly.cachefly.net)… 205.234.175.175
Connecting to cachefly.cachefly.net (cachefly.cachefly.net)|205.234.175.175|:80… connected.
HTTP request sent, awaiting response… 200 OK
Length: 10485760 (10M) [application/octet-stream]
Saving to: ‘/dev/null’

     0K …….. …….. …….. …….. …….. …….. 30%  142M 0s
  3072K …….. …….. …….. …….. …….. …….. 60%  179M 0s
  6144K …….. …….. …….. …….. …….. …….. 90%  204M 0s
  9216K …….. ……..                                    100%  197M=0.06s

2020-08-07 13:56:50 (173 MB/s) – ‘/dev/null’ saved [10485760/10485760]

Fri 07 Aug 2020 01:56:50 PM UTC


To be sure you have a real picture on remote machine Internet speed it is always a good idea to run download of random big files on a certain locations that are well known to have a very stable Internet bandwidth to the Internet backbone routers.

4. Using Simple shell script to test Internet speed


Fetch and use speedtest.sh

 


wget https://raw.github.com/blackdotsh/curl-speedtest/master/speedtest.sh && chmod u+x speedtest.sh && bash speedtest.sh

 

 

5. Using iperf to test connectivity between two servers 

 

iperf is another good tool worthy to mention that can be used to test the speed between client and server.

To use iperf install it with apt and do on the server machine to which bandwidth will be tested:

 

# iperf -s 

 

On the client machine do:

 

# iperf -c 192.168.1.1 

 

where 192.168.1.1 is the IP of the server where iperf was spawned to listen.

6. Using Netflix fast to determine Internet connection speed on host


Fast

fast is a service provided by Netflix. Its web interface is located at Fast.com and it has a command-line interface available through npm (npm is a package manager for nodejs) so if you don't have it you will have to install it first with:

# apt install –yes npm

 

Note that if you run on Debian this will install you some 249 new nodejs packages which you might not want to have on the system, so this is useful only for machines that has already use of nodejs.

 

$ fast

 

     82 Mbps ↓


The command returns your Internet download speed. To get your upload speed, use the -u flag:

 

$ fast -u

 

   ⠧ 80 Mbps ↓ / 8.2 Mbps ↑

 

7. Use speedometer / iftop to measure incoming and outgoing traffic on interface


If you're measuring connectivity on a live production server system, then you might consider that the measurement output might not be exactly correct especially if you're measuring the Uplink / Downlink on a Heavy loaded webserver / Mail Server / Samba or DNS server.
If this is the case a very useful tools to consider to extract the already taken traffic used on your Incoming and Outgoing ( TX / RX ) Network interfaces
are speedometer and iftop, they're present and installable depending on the OS via yum / apt or the respective package manager.

 


To install on Debian server:

 

 

 

# apt install –yes iftop speedometer

 


The most basic use to check the live received traffic in a nice Ncurses like text graphic is with: 

 

 

 

 

# speedometer -r 


speedometer-check-received-transmitted-network-traffic-on-linux1

To generate real time ASCII art graph on RX / TX traffic do:

 

 

# speedometer -r eth0 -t eth0


speedometer-check-received-transmitted-network-traffic-on-linux

 

 

 

 

# iftop -P -i eth0

 

 


iftop-show-statistics-on-connections-screenshot-pcfreak

 

 

 

 

 

Linux Send Monitoring Alert Emails without Mail Server via relay SMTP with ssmtp / msmtp

Friday, July 10th, 2020

ssmtp-linux-server-sending-email-without-a-local-mail-server-mta-relay-howto

If you have to setup a new Linux server where you need to do a certain local running daemons monitoring with a custom scripts on the local machine Nagios / Zabbix / Graphana etc. that should notify about local running custom programs or services in case of a certain criteria is matched or you simply want your local existing UNIX accounts to be able to send outbound Emails to the Internet.

Then usually you need to install a fully functional SMTP Email server that was Sendmail or QMAIL in old times in early 21st century andusually postfix or Exim in recent days and configure it to use as as a Relay mail server some Kind of SMTP.

The common Relay smtp setting would be such as Google's smtp.gmail.com, Yahoo!'s  smtp.mail.yahoo.com relay host, mail.com or External configured MTA Physical server with proper PTR / MX records or a SMTP hosted on a virtual machine living in Amazon's AWS or m$ Azure that is capable to delivere EMails to the Internet.

Configuring the local installed Mail Transport Agent (MTA) as a relay server is a relatively easy task to do but of course why should you have a fully stacked MTA service with a number of unnecessery services such as Email Queue, Local created mailboxes, Firewall rules, DNS records, SMTP Auth, DKIM keys etc. and even the ability to acccept any emails back in case if you just want to simply careless send and forget with a confirmation that remote email was send successfully?

This is often the case for some machines and especially with the inclusion of technologies such as Kubernettes / Clustered environments / VirtualMachines small proggies such as ssmtp / msmtp that could send mail without a Fully functional mail server installed on localhost ( 127.0.0.1 ) is true jams.

ssmtp program is Simple Send-only sendMail emulator  has been around in Debian GNU / Linux, Ubuntu, CentOS and mostly all Linuxes for quite some a time but recently the Debian package has been orphaned so to install it on a deb based server host you need to use instead msmtp.
 

1. Install ssmtp on CentOS / Fedora / RHEL Linux

In RPM distributions you can't install until epel-release repository is enabled.

[root@centos:~]# yum –enablerepo=extras install epel-release

[root@centos:~]# yum install ssmtp


2. Install ssmp / msmtp Debian / Ubuntu Linux

If you run older version of Debian based distribution the package to install is ssmtp, e.g.:

root@debian:~# apt-get install –yes ssmtp


On Newer Debians as of Debian 10.0 Buster onwards install instead

root@debian:~# apt install –yes msmtp-mta

can save you a lot of effort to keep an eye on a separately MTA hanging around and running as a local service eating up resources that could be spared.
 

3. Configure Relay host for ssmtp


A simple configuration to make ssmtp use gmail.com SMTP servers as a relay host below:

linux:~# cat << EOF > /etc/ssmtp/ssmtp.conf
# /etc/ssmtp/ssmtp.conf
# The user that gets all the mails (UID < 1000, usually the admin)
root=user@host.name
# The full hostname.  Must be correctly formed, fully qualified domain name or GMail will reject connection.
hostname=host.name
# The mail server (where the mail is sent to), both port 465 or 587 should be acceptable
# See also https://support.google.com/mail/answer/78799
mailhub=smtp.gmail.com:587
#mailhub=smtp.host.name:465

# The address where the mail appears to come from for user authentication.
rewriteDomain=gmail.com
# Email 'From header's can override the default domain?

FromLineOverride=YES

# Username/Password
AuthUser=username@gmail.com
AuthPass=password
AuthMethod=LOGIN
# Use SSL/TLS before starting negotiation
UseTLS=YES
UseTLS=Yes
UseSTARTTLS=Yes
logfile        ~/.msmtp.log

EOF

This configuration is very basic and it is useful only if you don't want to get delivered mails back as this functionality is also supported even though rarely used by most.

One downside of ssmtp is mail password will be plain text, so make sure you set proper permissions to /etc/ssmtp/ssmtp.conf
 

– If your Gmail account is secured with two-factor authentication, you need to generate a unique App Password to use in ssmtp.conf. You can do so on your App Passwords page. Use Gmail username (not the App Name) in the AuthUser line and use the generated 16-character password in the AuthPass line, spaces in the password can be omitted.

– If you do not use two-factor authentication, you need to allow access to unsecure apps.
 

4. Configuring different msmtp for separate user profiles


SSMTP is capable of respecting multiple relays for different local UNIX users assuming each of whom has a separate home under /home/your-username

To set a certain user lets say georgi to relay smtp sent emails with mail or mailx command create ~/.msmtprc

 

linux:~# vim ~/.msmtprc


Append configuration like:

# Set default values for all following accounts.
defaults
port 587
tls on
tls_trust_file /etc/ssl/certs/ca-certificates.crt
account gmail
host smtp.gmail.com
from <user>@gmail.com
auth on
user <user>
passwordeval gpg –no-tty -q -d ~/.msmtp-gmail.gpg
# Set a default account

account default : gmail


To add it for any different user modify the respective fields and set the different Mail hostname etc.
 

5. Using mail address aliases


msmtp also supports mail aliases, to make them work you will need to have file /etc/msmptrc with
 

aliases               /etc/aliases


Standard aliasses them should work 

linux:~# cat /etc/aliases
# Example aliases file
     
# Send root to Joe and Jane
root: georgi_georgiev@example.com, georgi@example.com
   
# Send everything else to admin
default: admin@domain.example

 

6. Get updated when your Debian servers have new packages to update 

msmpt can be used for multiple stuff one example use would be to use it together with cron to get daily updates if there are new debian issued security or errata update pending packages, to do so you can use the apticron shell script.

To use it on debian install the apticron pack:
 

root@debian:~# apt-get install –yes apticron

apticron has the capability to:

 * send daily emails about pending upgrades in your system;
 * give you the choice of receiving only those upgrades not previously notified;
 * automatically integrate to apt-listchanges in order to give you by email the
   new changes of the pending upgrade packages;
 * handle and warn you about packages put on hold via aptitude/dselect,
   avoiding unexpected package upgrades (see #137771);
 * give you all these stuff in a simple default installation;

 

To configure it you have to place a config copy the one from /usr/lib/apticron/apticron.conf to /etc/apticron/apticron.conf

The only important value to modify in the config is the email address to which an apt-listchanges info for new installable debs from the apt-get dist-upgrade command. Output from them will be be send to the configured EMAIL field  in apticron.conf.
 

EMAIL="<your-user@email-addr-domain.com>"


The timing at which the offered new pending package update reminder will be sent is controlled by /etc/cron.d/apticron
 

debian:~# cat /etc/cron.d/apticron
# cron entry for apticron

48 * * * * root if test -x /usr/sbin/apticron; then /usr/sbin/apticron –cron; else true; fi

apticron will use the local previous ssmtp / msmpt program to deliver to configured mailbox.
To manually trigger apticron run:
 

root@debian:~# if test -x /usr/sbin/apticron; then /usr/sbin/apticron –cron; else true; fi


7. Test whether local mail send works to the Internet

To test mail sent we can use either mail / mailx or sendmail command or some more advanced mailer as alpine or mutt.

Below is few examples.

linux:~$ echo -e "Subject: this is the subject\n\nthis is the body" | mail user@your-recipient-domain.com

To test attachments to mail also works run:

linux:~$ mail -s "Subject" recipient-email@domain.com < mail-content-to-attach.txt

or

Prepare the mail you want to send and send it with sendmail

linux:~$ vim test-mail.txt
To:username@example.com
From:youraccount@gmail.com
Subject: Test Email
This is a test mail.

linux:~$ sendmail -t < test-mail.txt

Sending encoded atacchments with uuencode is also possible but you will need sharutils Deb / RPM package installed.

To attach lets say 2 simple text files uuencoded:

linux:~$ uuencode file.txt myfile.txt | sendmail user@example.com

echo "

To: username@domain.com From: username@gmail.com Subject: A test Hello there." > test.mail

linux:~$ cat test.mail | msmtp -a default <username>@domain.com


That's all folks, hope you learned something, if you know of some better stuff like ssmtp please shar e it.

Automatic network restart and reboot Linux server script if ping timeout to gateway is not responding as a way to reduce connectivity downtimes

Monday, December 10th, 2018

automatic-server-network-restart-and-reboot-script-if-connection-to-server-gateway-inavailable-tux-penguing-ascii-art-bin-bash

Inability of server to come back online server automaticallyafter electricity / network outage

These days my home server  is experiencing a lot of issues due to Electricity Power Outages, a construction dig operations to fix / change waterpipe tubes near my home are in action and perhaps the power cables got ruptered by the digger machine.
The effect of all this was that my server networking accessability was affected and as I didn't have network I couldn't access it remotely anymore at a certain point the electricity was restored (and the UPS charge could keep the server up), however the server accessibility did not due restore until I asked a relative to restart it or under a more complicated cases where Tech aquanted guy has to help – Alexander (Alex) a close friend from school years check his old site here – alex.www.pc-freak.net helps a lot.to restart the machine physically either run a quick restoration commands on root TTY terminal or generally do check whether default router is reachable.

This kind of Pc-Freak.net downtime issues over the last month become too frequent (the machine was down about 5 times for 2 to 5 hours and this was too much (and weirdly enough it was not accessible from the internet even after electricity network was restored and the only solution to that was a physical server restart (from the Power Button).

To decrease the number of cases in which known relatives or friends has to  physically go to the server and restart it, each time after network or electricity outage I wrote a small script to check accessibility towards Default defined Network Gateway for my server with few ICMP packages sent with good old PING command
and trigger a network restart and system reboot
(in case if the network restart does fail) in a row.

1. Create reboot-if-nwork-is-downsh script under /usr/sbin or other dir

Here is the script itself:

 

#!/bin/sh
# Script checks with ping 5 ICMP pings 10 times to DEF GW and if so
# triggers networking restart /etc/inid.d/networking restart
# Then does another 5 x 10 PINGS and if ping command returns errors,
# Reboots machine
# This script is useful if you run home router with Linux and you have
# electricity outages and machine doesn't go up if not rebooted in that case

GATEWAY_HOST='192.168.0.1';

run_ping () {
for i in $(seq 1 10); do
    ping -c 5 $GATEWAY_HOST
done

}

reboot_f () {
if [ $? -eq 0 ]; then
        echo "$(date "+%Y-%m-%d %H:%M:%S") Ping to $GATEWAY_HOST OK" >> /var/log/reboot.log
    else
    /etc/init.d/networking restart
        echo "$(date "+%Y-%m-%d %H:%M:%S") Restarted Network Interfaces:" >> /tmp/rebooted.txt
    for i in $(seq 1 10); do ping -c 5 $GATEWAY_HOST; done
    if [ $? -eq 0 ] && [ $(cat /tmp/rebooted.txt) -lt ‘5’ ]; then
         echo "$(date "+%Y-%m-%d %H:%M:%S") Ping to $GATEWAY_HOST FAILED !!! REBOOTING." >> /var/log/reboot.log
        /sbin/reboot

    # increment 5 times until stop
    [[ -f /tmp/rebooted.txt ]] || echo 0 > /tmp/rebooted.txt
    n=$(< /tmp/rebooted.txt)
        echo $(( n + 1 )) > /tmp/rebooted.txt
    fi
    # if 5 times rebooted sleep 30 mins and reset counter
    if [ $(cat /tmprebooted.txt) -eq ‘5’ ]; then
    sleep 1800
        cat /dev/null > /tmp/rebooted.txt
    fi
fi

}
run_ping;
reboot_f;

You can download a copy of reboot-if-nwork-is-down.sh script here.

As you see in script successful runs  as well as its failures are logged on server in /var/log/reboot.log with respective timestamp.
Also a counter to 5 is kept in /tmp/rebooted.txt, incremented on each and every script run (rebooting) if, the 5 times increment is matched

a sleep is executed for 30 minutes and the counter is being restarted.
The counter check to 5 guarantees the server will not get restarted if access to Gateway is not continuing for a long time to prevent the system is not being restarted like crazy all time.
 

2. Create a cron job to run reboot-if-nwork-is-down.sh every 15 minutes or so 

I've set the script to re-run in a scheduled (root user) cron job every 15 minutes with following  job:

To add the script to the existing cron rules without rewriting my old cron jobs and without tempering to use cronta -u root -e (e.g. do the cron job add in a non-interactive mode with a single bash script one liner had to run following command:

 

{ crontab -l; echo "*/15 * * * * /usr/sbin/reboot-if-nwork-is-down.sh 2>&1 >/dev/null; } | crontab –


I know restarting a server to restore accessibility is a stupid practice but for home-use or small client servers with unguaranteed networks with a cheap Uninterruptable Power Supply (UPS) devices it is useful.

Summary

Time will show how efficient such a  "self-healing script practice is.
Even though I'm pretty sure that even in a Corporate businesses and large Public / Private Hybrid Clouds where access to remote mounted NFS / XFS / ZFS filesystems are failing a modifications of the script could save you a lot of nerves and troubles and unhappy customers / managers screaming at you on the phone 🙂


I'll be interested to hear from others who have a better  ideas to restore ( resurrect ) access to inessible Linux server after an outage.?
 

Optimize PNG images by compressing on GNU / Linux, FreeBSD server to Improve Website overall Performance

Monday, November 27th, 2017

how-to-optimize-your-png-pictures-to-reduce-size-and-save-speed-bandwidth-optipng-compression-tests-results

If you own a website with some few hundreds of .PNG images like 10 000 / 15 000 png images and the website shows to perform slow in Google PageSpeed Insights and is slow to open when Google Searched or Shared on Facebook / Twitter etc. then one recommended step to boost up the website opening speed is to compress (optimize) the .PNG pictures without loosing the images quality to both save space and account bandwidth you could use optipng even though this is not the only tool available to help you optimize and reduce the size of your images, some few other tools you might like to check out if you have more time are:

 a.)  pngcrush – optimizes PNG (Portable Network Graphics) files.
 b.)  pngnq – tool for optimizing PNG (Portable Network Graphics) images. It is a tool for quantizing PNG images in RGBA format.
 c.)  pngquant – PNG (Portable Network Graphics) image optimising utility. It is a command-line utility for converting 24/32-bit PNG images to paletted (8-bit) PNGs.
 

1. Install and Compress / optimize PNG / GIF / PNM / TIFF file format with optipng
 

OPTIPING tool recompresses the .PNG images to a smaller size without loosing any quality information, besides PNG file format it also supports (BMP, GIF, PNM and TIFF) image format.

If you don't have optipng installed on your server you can;

a.) install it on Redhat RPM based Linux distributions lets say CentOS Linux use:

 

[root@centos: ~]# yum install epel-release
[root@centos: ~]# yum install optipng

Note that, You will need to  first enable epel repo on centos 7

 

b.) If instead you're on a Debian GNU / Linux

debian:~# apt-get install optipng


c.) FreeBSD users can install it from FreeBSD ports with:

 

freebsd# cd /usr/ports/graphics/optipng
freebsd# make install clean

optipng syntax is quite self explanatory
optipng [options] what-ever-file.png


You can get a full list of possible command options with -? command, here is a list:

 

debian:~# optipng -?
Synopsis:
    optipng [options] files …
Files:
    Image files of type: PNG, BMP, GIF, PNM or TIFF
Basic options:
    -?, -h, -help    show this help
    -o <level>        optimization level (0-7)        [default: 2]
    -v            run in verbose mode / show copyright and version info
General options:
    -backup, -keep    keep a backup of the modified files
    -clobber        overwrite existing files
    -fix        enable error recovery
    -force        enforce writing of a new output file
    -preserve        preserve file attributes if possible
    -quiet, -silent    run in quiet mode
    -simulate        run in simulation mode
    -out <file>        write output file to <file>
    -dir <directory>    write output file(s) to <directory>
    -log <file>        log messages to <file>
    —            stop option switch parsing
Optimization options:
    -f <filters>    PNG delta filters (0-5)            [default: 0,5]
    -i <type>        PNG interlace type (0-1)
    -zc <levels>    zlib compression levels (1-9)        [default: 9]
    -zm <levels>    zlib memory levels (1-9)        [default: 8]
    -zs <strategies>    zlib compression strategies (0-3)    [default: 0-3]
    -zw <size>        zlib window size (256,512,1k,2k,4k,8k,16k,32k)
    -full        produce a full report on IDAT (might reduce speed)
    -nb            no bit depth reduction
    -nc            no color type reduction
    -np            no palette reduction
    -nx            no reductions
    -nz            no IDAT recoding
Editing options:
    -snip        cut one image out of multi-image or animation files
    -strip <objects>    strip metadata objects (e.g. "all")
Optimization levels:
    -o0        <=>    -o1 -nx -nz                (0 or 1 trials)
    -o1        <=>    -zc9 -zm8 -zs0 -f0            (1 trial)
            (or…)    -zc9 -zm8 -zs1 -f5            (1 trial)
    -o2        <=>    -zc9 -zm8 -zs0-3 -f0,5            (8 trials)
    -o3        <=>    -zc9 -zm8-9 -zs0-3 -f0,5        (16 trials)
    -o4        <=>    -zc9 -zm8 -zs0-3 -f0-5            (24 trials)
    -o5        <=>    -zc9 -zm8-9 -zs0-3 -f0-5        (48 trials)
    -o6        <=>    -zc1-9 -zm8 -zs0-3 -f0-5        (120 trials)
    -o7        <=>    -zc1-9 -zm8-9 -zs0-3 -f0-5        (240 trials)
    -o7 -zm1-9    <=>    -zc1-9 -zm1-9 -zs0-3 -f0-5        (1080 trials)
Notes:
    The combination for -o1 is chosen heuristically.
    Exhaustive combinations such as "-o7 -zm1-9" are not generally recommended.
Examples:
    optipng file.png                        (default speed)
    optipng -o5 file.png                    (slow)
    optipng -o7 file.png                    (very slow)

Just running it with, lets say -o7 arguments is enough for optipng to compress your image and reduce some 15 to 30% of picture size

optipng -o7 what-ever-image-you-have.png

optipng-example-on-reducing-image-screenshot-24.9-png-image-compression

2. Compress images without loosing quality recursively inside directory and subdirectories with optiping

a.) To optimize all pictures inside a single directory (without sub-directories) on remote server you can run, below command:
 

cd whatever-dir/
for i in *.png; do optipng -o6 -quiet -keep -preserve -dir optimized -log optipng-compress.log "$i"; done


As you can see a log is being written on what the command has done and the originals of the optimized images is going to be preserved, the optimize level is 6 is the PNG encoding level.

 

cd /var/www/your-site/images/
find . -type f -iname "*.png" -print0 | xargs -I {} -0 optipng -o6 -keep -preserve -log optipng-compress.log "{}"


This command is pretty handy to run on own dedicated server, if you don't have one just do it on your Linux computer at home or if you don't own a PC with Linux install any Deb / RPM based Linux inside VirtualBox or VMWare Virtual Machine and do it there, then upload to your Hosting Provider / Amazon EC2 etc and Enjoy the increased website performance 🙂

 

Add gzip compression to optimize web server served files in Apache, Nginx and LiteSpeed

Wednesday, November 15th, 2017

Enable-Gzip-Compression-quick-howto-on-apache-nginx-litespeed

What is GZIP Compression and why you need it?

no-gzip-support-illustration

  • What is gzip? – In Linux / Unix gzip of files is used to compress files so they can take less space when they're transferred from server to server via network in order to speed up file transfer.
  • Usually gzipped files are named as filename.gz
  • Why GZIp compression is important to be enabled on servers, well because that reduces the transferred (served) file by webserver to client browser
  • The effect of this is the faster file transfer of the file and increased overall web user performance


how-gzip-works-with-nginx-illustrated

Most webservers / websites online currently use gzipping of a sort, those who still did not use it has websites which are up to 40% slower than those of competitor websites

How to enable GZIP Compression on Apache Webserver

The easiest way for most people out there who run there websites on a shared hosting is to add the following Apache directives to dynamic loadable .htaccess file:
 

<ifModule mod_gzip.c>
mod_gzip_on Yes
mod_gzip_dechunk Yes
mod_gzip_item_include file .(html?|txt|css|js|php|pl)$
mod_gzip_item_include handler ^cgi-script$
mod_gzip_item_include mime ^text/.*
mod_gzip_item_include mime ^application/x-javascript.*
mod_gzip_item_exclude mime ^image/.*
mod_gzip_item_exclude rspheader ^Content-Encoding:.*gzip.*
</ifModule>

 

You can put a number of other useful things in .htaccess the file should already be existing in most webhostings with Cpanel or Kloxo kind of administration management interface.

Once the code is included to .htaccess you can reflush site cache.
To test whether the just added HTTP gzip compression works for the Webserver you can use The Online HTTP Compression test

If for some reason after adding this code you don't rip the benefits of gzipped content served by webserver you can try to add altenatively to .htaccess

 

AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE application/x-javascript

 


Howto Enable GZIP HTTP file compression on NGINX Webserver?

Open NGINX configuration file and add to it the following command parameters:

 

gzip on;
gzip_comp_level 2;
gzip_http_version 1.0;
gzip_proxied any;
gzip_min_length 1100;
gzip_buffers 16 8k;
gzip_types text/plain text/html text/css application/x-javascript text/xml application/xml application/xml+rss text/javascript;

 

# Disable for IE < 6 because there are some known problems
gzip_disable "MSIE [1-6].(?!.*SV1)";

# Add a vary header for downstream proxies to avoid sending cached gzipped files to IE6
gzip_vary on;

Enable HTTP file Compression on LiteSpeed webserver

In configuration under TUNING section check whether "enable compression" is enabled, if it is not choose "Edit"
and turn it on.

litespeed-how-to-enable-gzip-compressible_type-illustrated

What is the speed benefits of using HTTP gzip compression?

By using HTTP gzip compression you can save your network and clients abot 50 to 70% (e.g. transferred data) of the original file size.
This would mean less time for loading pages and fetched files and decrease in used bandwidth.

effect-of-gzip-compression-diagram-illustrated

A very handy tool to test whether HTTP Compression is enabled as well as how much is optimized for Speed your Website is Google PageSpeed Insights
as well as GTMetrix.com

Where are Apache log files on my server – Apache log file locations on Debian / Ubuntu / CentOS / Fedora and FreeBSD ?

Tuesday, November 7th, 2017

apache-where-are-httpd-access-log-files

Where are Apache log files on my server?

1. Finding Linux / FreeBSD operating system distribtion and version

Before finding location of Apache log files it is useful to check what is the remote / local Linux operating system version, hence

First thing to do when you login to your remote Linux server is to check what kind of GNU / Linux you're dealing with:

cat /etc/issue
cat /etc/issue.net


In most GNU / Linux distributions should give you enough information about the exact Linux distribution and version remote server is running.

You will get outputs like

# cat /etc/issue
SUSE LINUX Enterprise Server 10.2 Kernel \r (\m), \l

or

# cat /etc/issue
Debian GNU/Linux 8 \n \l

If remote Linux is Fedora look for fedora-release file:

cat /etc/fedora-release Fedora release 7 (Moonshine)

The proposed freedesktop.org standard with the introduction of systemd across all Linux distributions is

/etc/os-release

 

# cat /etc/os-release
PRETTY_NAME="Debian GNU/Linux 8 (jessie)"
NAME="Debian GNU/Linux"
VERSION_ID="8"
VERSION="8 (jessie)"
ID=debian
HOME_URL="http://www.debian.org/"
SUPPORT_URL="http://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"


Once we know what kind of Linux distribution we're dealing with, we can proceed with looking up for standard location of Apache config:

2. Apache config file location for Fedora / CentOS / RHEL and other RPM based distributions

RHEL / Red Hat / CentOS / Fedora Linux Apache access file location
 

/var/log/httpd/access_log


3. Apache config file location for Debian / Ubuntu and other deb based Linux distributions

Debian / Ubuntu Linux Apache access log file location

/var/log/apache2/access.log


4. Apache config file location for FreeBSD

FreeBSD Apache access log file location –

/var/log/httpd-access.log


5. Finding custom Apache access log locations
 

If for some reason the system administrator on the remote server changed default path for each of distributions, you can find custom configured log files through:

a) On Debian / Ubuntu / deb distros:

debian:~# grep CustomLog /etc/apache2/apache2.conf


b) On CentOS / RHEL / Fedora Linux RPM based ones:

[root@centos:  ~]# grep CustomLog /etc/httpd/conf/httpd.conf


c) On FreeBSD OS

 

freebsd# grep CustomLog /etc/httpd/conf/httpd.conf
 # a CustomLog directive (see below).
    #CustomLog "/var/log/httpd-access.log" common
    CustomLog "/var/log/httpd-access.log" combined