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Linux extending life time for a damaged hard drive server tricks on a live server. Force fcsk on next reboot.Read-only file system error solutions

Friday, February 17th, 2023

linux-extending-life-time-for-a-damaged-hard-drive-server-tricks-can-not-read-superblock-linux-force-fsck-on-next-reboot

In our daily work as system administrators we have some very old Legacy systems running Clustered High Availability proxies using CRM (Cluster Resource Manager) and some legacy systems still using Heartbeat to manage the cluster instead of the newer and modern Corosync variant.

The HA cluster is only 2 nodes Linux machine and running the obscure already long time unsupported version of Redhat 5.11 (Ootpa) who was officially became stable distant year 1998 (yeath the years were good) and whose EOL (End of Life) has been reached long time ago and the OS is no longer supported, however for about 14 years the machines has been running perfectly fine until one of the Cluster nodes managed by ocf::heartbeat:IPAddr2 , that is  /etc/ha.d/resource.d/IPAddr2 shell script. Yeah for the newbies Heartbeat Application Cluster in Linux does work like that it uses a number of extendable pair of shell scripts written for different kind of Network / Web / Mail / SQL or whatever services HA management.

The first node configured however, started failing due to some errors like:
 

EXT3-fs error (device dm-1): ext3_journal_start_sb: Detected aborted journal
sd 0:2:0:0: rejecting I/O to offline device
Aborting journal on device sda1.
sd 0:2:0:0: rejecting I/O to offline device
printk: 159 messages suppressed.
Buffer I/O error on device sda1, logical block 526
lost page write due to I/O error on sda1
sd 0:2:0:0: rejecting I/O to offline device
sd 0:2:0:0: rejecting I/O to offline device
ext3_abort called.
EXT3-fs error (device sda1): ext3_journal_start_sb: Detected aborted journal
Remounting filesystem read-only
sd 0:2:0:0: rejecting I/O to offline device
sd 0:2:0:0: rejecting I/O to offline device
sd 0:2:0:0: rejecting I/O to offline device
sd 0:2:0:0: rejecting I/O to offline device
sd 0:2:0:0: rejecting I/O to offline device
megaraid_sas: FW was restarted successfully, initiating next stage…
megaraid_sas: HBA recovery state machine, state 2 starting…
megasas: Waiting for FW to come to ready state
megasas: FW in FAULT state!!
FW state [-268435456] hasn't changed in 180 secs
megaraid_sas: out: controller is not in ready state
megasas: waiting_for_outstanding: after issue OCR. 
megasas: waiting_for_outstanding: before issue OCR. FW state = f0000000
megaraid_sas: pending commands remain even after reset handling. megasas[0]: Dumping Frame Phys Address of all pending cmds in FW
megasas[0]: Total OS Pending cmds : 0 megasas[0]: 64 bit SGLs were sent to FW
megasas[0]: Pending OS cmds in FW :

The result out of that was a frequently the filesystem of the machine got re-mounted as Read Only and of course that is
quite bad if you have a running processess of haproxy that should be able to be living their and take up some Web traffic
for high availability and you run all the traffic only on the 2nd pair of machine.

This of course was a clear sign for a failing disks or some hit bad blocks regions or as the messages indicates, some
problem with system hardware or Raid SAS Array.

The physical raid on the system, just like rest of the hardware is very old stuff as well.

[root@haproxy_lb_node1 ~]# lspci |grep -i RAI
01:00.0 RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS 2108 [Liberator] (rev 05)

The produced errors not only made the machine to auto-mount its root / filesystem in Read-Only mode but besides has most
likely made the machine to automatically reboot every few days or few times every day in a raw.

The second Load Balancer node2 did operated perfectly, and we thought that we might just keep the broken machine in that half running
and inconsistent state for few weeks until we have built the new machines with Pre-Installed new haproxy cluster with modern
RedHat Linux 8.6 distribution, but since we have to follow SLAs (Service Line Agreements) with Customers and the end services behind the
High Availability (HA) Haproxy cluster were at danger … 

We as sysadmins had the task to make our best to try to stabilize the unstable node with disk errors for the system to servive
and be able to normally serve traffic (if node2 that is in a separate Data center fails due to a hardware or electricity issues etc.).

Here is few steps we took, that has hopefully improved the situation.

1. Make backups of most important files of high importance

Always before doing anything with a broken system, prepare backup of the most important files, if that is a cluster that should be a backup of the cluster configurations (if you don't have already ones) backup of /etc/hosts / backup of any important services configs /etc/haproxy/haproxy.cfg /etc/postfix/postfix.cfg (like it was my case), preferrably backup of whole /etc/  any important files from /root/ or /home/users* directories backup of at leasts latest logs from /var/log etc.
 

2. Clear up all unnecessery services scripts from the server

Any additional Softwares / Services and integrity checking tools (daemons) / scripts and cron jobs, were immediately stopped and wheter unused removed.

E.g. we had moved through /etc/cron* to check what's there,

# ls -ld /etc/cron.*
drwx—— 2 root root 4096 Feb  7 18:13 /etc/cron.d
drwxr-xr-x 2 root root 4096 Feb  7 17:59 /etc/cron.daily
-rw-r–r– 1 root root    0 Jul 20  2010 /etc/cron.deny
drwxr-xr-x 2 root root 4096 Jan  9  2013 /etc/cron.hourly
drwxr-xr-x 2 root root 4096 Jan  9  2013 /etc/cron.monthly
drwxr-xr-x 2 root root 4096 Aug 26  2015 /etc/cron.weekly

 

And like well professional butchers removed everything unnecessery that could trigger any extra unnecessery disk read / writes to HDD.

E.g. just create

# mkdir -p /root/etc_old/{/etc/cron.d,\
/etc/cron.daily,/etc/cron.hourly,/etc/cron.monthly\
,/etc/cron.weekly}

 

And moved all unnecessery cron job scripts like:

1. nmon (old school network / memory / hard disk console tool for monitoring and tuning server parameters)
2. clamscan / freshclam crons
3. mlocate (the script that is taking care for periodic run of updatedb command to keep the locate command to easily search
for files inside the DB to put less read operations on disk in case if you need to find file (e.g. prevent yourself to everytime
run cmd like: find / . -iname '*whatever_you_look_for*'
4. cups cron jobs
5. logwatch cron
6. rkhunter stuff
7. logrotate (yes we stopped even logrotation trigger job as we found the server was crashing sometimes at the same time when
the lograte job to rotate logs inside /var/log/* was running perhaps leading to a hit of the I/O read error (bad blocks).


Also inspected the Administrator user root cron job for any unwated scripts and stopped two report bash scripts that were part of the PCI tightened Security procedures.
Therein found script responsible to periodically report the list of installed packages and if they have not changed, as well a script to periodically report via email the list of
/etc/{passwd,/etc/shadow} created users, used to historically keep an eye on the list of users and easily see if someone
has created new users on the machine. Those were enabled via /var/spool/cron/root cron jobs, in other cases, on other machines if it happens for you
it is a good idea to check out all the existing user cron jobs and stop anything that might be putting Read / Write extra heat pressure on machine attached the Hard drives.

# ls -al /var/spool/cron/
total 20
drwx——  2 root root 4096 Nov 13  2015 .
drwxr-xr-x 12 root root 4096 May 11  2011 ..
-rw——-  1 root root  133 Nov 13  2015 root


3. Clear up old log files and any files unnecessery

Under /var/log and /home /var/tmp /var/spool/tmp immediately try to clear up the old log files.
From my past experience this has many times made the FS file inodes that are storing on a unbroken part (good blocks) of the hard drive and
ready to be reused by newly written rsyslog / syslogd services spitted files.

!!! Note that during the removal of some files you might hit a files stored on a bad blocks that might lead to a unexpected system reboot.

But that's okay, don't worry most likely after a hard reset by a technician in the Datacenter the machine will boot again and you can enjoy
removing remaining still files to send them to the heaven for old files.
 

4. Trigger an automatic system file system check with fsck on next boot

The standard way to force a Linux to aumatically recheck its Root filesystem is to simply create the /forcefsck to root partition or any other secondary disk partition you would like to check.

# touch /forcefsck

# reboot


However at some occasions you might be unable to do it because, the / (root fs) has been remounted in ReadOnly mode, yackes …

Luckily old Linux distibutions like this RHEL 5.1, has a way to force a filesystem check after reboot fsck and identify any
unknown bad-blocks and hopefully succceed in isolating them, so you don't hit into the same auto-reboots if the hard drive or Software / Hardware RAID
is not in terrible state, you can use an option built in in /sbin/shutdown command the '-F'

   -F     Force fsck on reboot.


Hence to make the machine reboot and trigger immediately fsck:

# shutdown -rF now


Just In case you wonder why to reboot before check the Filesystem. Well simply because you need to have them unmounted before you check.

In that specific case this produced so far a good result and the machine booted just fine and we crossed the fingers and prayed that the machine would work flawlessly in the coming few weeks, before we finalize the configuration of the substitute machines, where this old infrastructure will be migrated to a new built cluster with new Haproxy and Corosync / Pacemaker Cluster on a brand new RHEL.

NB! On newer machines this won't work however as shutdown command has been stripped off this option because no SystemV (SystemInit) or Upstart and not on SystemD newer services architecture.
 

5. Hints on checking the hard drives with fsck

If you happen to be able to have physical access to the remote Hardare machine via a TTY[1-9] Console, that's even better and is the standard way to do it but with this specific case we had no easy way to get access to the Physical server console.

It is even better to go there and via either via connected Monitor (Display) or KVM Switch (Those who hear KVM switch first time this is a great device in server rooms to connect multiple monitors to same Monitor Display), it is better to use a some of the multitude of options to choose from for USB Distro Linux recovery OS versions or a CDROM / DVD on older machines like this with the Redhat's recovery mode rolled on.
After mounting the partition simply check each of the disks
e.g. :

# fsck -y /dev/sdb
# fsck -y /dev/sdc

Or if you want to not waste time and look for each hard drive but directly check all the ones that are attached and known by Linux distro via /etc/fstab definition run:

# fsck -AR

If necessery and you have a mixture of filesystems for example EXT3 , EXT4 , REISERFS you can tell it to omit some filesystem, for example ext3, like that:

# fsck -AR -t noext3 -y


To skip fsck on mounted partitions with fsck:

# fsck -M /dev/sdb


One remark to make here on fsck is usually fsck to complete its job on various filesystem it uses other external component binaries usually stored in /sbin/fsck*

# ls -al /sbin/fsck*
-rwxr-xr-x 1 root root  55576 20 яну 2022 /sbin/fsck*
-rwxr-xr-x 1 root root  43272 20 яну 2022 /sbin/fsck.cramfs*
lrwxrwxrwx 1 root root      9  4 юли 2020 /sbin/fsck.exfat -> exfatfsck*
lrwxrwxrwx 1 root root      6  7 юни 2021 /sbin/fsck.ext2 -> e2fsck*
lrwxrwxrwx 1 root root      6  7 юни 2021 /sbin/fsck.ext3 -> e2fsck*
lrwxrwxrwx 1 root root      6  7 юни 2021 /sbin/fsck.ext4 -> e2fsck*
-rwxr-xr-x 1 root root  84208  8 фев 2021 /sbin/fsck.fat*
-rwxr-xr-x 2 root root 393040 30 ное 2009 /sbin/fsck.jfs*
-rwxr-xr-x 1 root root 125184 20 яну 2022 /sbin/fsck.minix*
lrwxrwxrwx 1 root root      8  8 фев 2021 /sbin/fsck.msdos -> fsck.fat*
-rwxr-xr-x 1 root root    333 16 дек 2021 /sbin/fsck.nfs*
lrwxrwxrwx 1 root root      8  8 фев 2021 /sbin/fsck.vfat -> fsck.fat*


6. Using tune2fs to  adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems (few examples)

a) To check whether really the filesystem was checked on boot time or check a random filesystem on the server for its last check up date with fsck:

#  tune2fs -l /dev/sda1 | grep checked
Last checked:             Wed Apr 17 11:04:44 2019

On some distributions like old Debian and Ubuntu, it is even possible to enable fsck to log its operations during check on reboot via changing the verbosity from NO to YES:

# sed -i "s/#VERBOSE=no/VERBOSE=yes/" /etc/default/rcS


If you're having the issues on old Debian Linuxes  and not on RHEL  it is possible to;

b) Enable all fsck repairs automatic on boot

by running via:
 

# sed -i "s/FSCKFIX=no/FSCKFIX=yes/" /etc/default/rcS


c) Forcing fcsk check on for server attached Hard Drive Partitions with tune2fs

# tune2fs -c 1 /dev/sdXY

Note that:
tune2fs can force a fsck on each reboot for EXT4, EXT3 and EXT2 filesystems only.

tune2fs can trigger a forced fsck on every reboot using the -c (max-mount-counts) option.
This option sets the number of mounts after which the filesystem will be checked, so setting it to 1 will run fsck each time the computer boots.
Setting it to -1 or 0 resets this (the number of times the filesystem is mounted will be disregarded by e2fsck and the kernel).


 For example you could:

d) Set fsck to run a filesystem check every 30 boots, by using -c 30 
 

# tune2fs -c 30 /dev/sdXY


e) Checking whether a Hard Drive has been really checked on the boot

 

#  tune2fs -l /dev/sda1 | grep checked
Last checked:             Wed Apr 17 11:04:44 2019


e) Check when was the last time the file system /dev/sdX was checked:
 

# tune2fs -l /dev/sdX | grep Last\ c
Last checked:             Thu Jan 12 20:28:34 2017


f) Check how many times our /dev/sdX filesystem was mounted

# tune2fs -l /dev/sdX | grep Mount
Mount count:              157

g) Check how many mounts are allowed to pass before filesystem check is forced
 

# tune2fs -l /dev/sdX | grep Max
Maximum mount count:      -1


7. Repairing disk / partitions via GRUB fsck.mode and fsck.repair kernel module options

It is also possible to force a fsck.repair on boot via GRUB, but that usually is not an option someone would like as the machine might fail too boot if it hards to repair hardly, however in difficult situations with failing disks temporary enabling it is good idea.

This can be done by including for grub initial config

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash fsck.mode=force fsck.repair=yes"

fsck.mode=force – will force a fsck each time a system boot and keeping that value enabled for a long time inside GRUB is stupid for servers as

sometimes booting could be severely prolonged because of the checks especially with servers with many or slow old hard drives.

fsck.repair=yes – will make the fsck try to repair if it finds bad blocks when checking (be absolutely sure you know, what you're doing if passing this options)

The options can be also set via editing the GRUB boot screen, if you have physical access to the server and don't want to reload the grub loader and possibly make the machine unbootable on next boot.
 

8. Few more details on how /etc/fstab disk fsck check parameters values for Systemd Linux machines works

The "proper" way on systemd (if we can talk about proper way on Linux) to runs fsck for each filesystem that has a fsck is to pass number greater than 0 set in
/etc/fstab (last column in /etc/fstab), so make sure you edit your /etc/fstab if that's not the case.

The root partition should be set to 1 (first to be checked), while other partitions you want to be checked should be set to 2.

Example /etc/fstab:
 

# /etc/fstab: static file system information.

/dev/sda1  /      ext4  errors=remount-ro  0  1
/dev/sda5  /home  ext4  defaults           0  2

The values you can put here as a second number meaning is as follows:
0 – disabled, that is do not check filesystem
1 – partition with this PASS value has a higher priority and is checked first. This value is usually set to the root / partition
2 – partitions with this PASS value will be checked last

a) Check the produced log out of fsck

Unfortunately on the older versions of Linux distros with SystemV fsck log output might be not generated except on the physical console so if you have a kind of duplicator device physical tty on the display port of the server, you might capture some bad block reports or fixed errors messages, but if you don't you might just cross the fingers and hope that anything found FS irregularities was recovered.

On systemd Linux machines the fsck log should be produced either in /run/initramfs/fsck.log or some other location depending on the Linux distro and you should be able to see something from fsck inside /var/log/* logs:

# grep -rli fsck /var/log/*


Close it up

Having a system with failing disk is a really one of the worst sysadmin nightmares to get. The good news is that most of the cases we're prepared with some working backup or some work around stuff like the few steps explained to mitigate the amount of Read / Writes to hard disks on the failing machine HDDs. If the failing disk is a primary Linux filesystem all becomes even worse as every next reboot, you have no guarantee, whether the kernel / initrd or some of the other system components required to run the Core Linux system won't break up the normal boot. Thus one side changes on the hard drives is a risky business on ther other side, if you're in a situation where you have a mirror system or the failing system is just a Linux server installed without a Cluster pair, then this is not a big deal as you can guarantee at least one of the nodes still up, unning and serving. Still doing too much of operations with HDD is always a danger so the steps described, though in most cases leading to improvement on how the system behaves, the system should be considered totally unreliable and closely monitored not only by some monitoring stuff like Zabbix / Prometheus whatever but regularly check the systems state via normal SSH logins. It is important if you have some important datas or logs on the system that are not synchronized to a system node to copy them before doing any of the described operations. After all minimal is backuped, proceed to clear up everything that might be cleared up and still the machine to continue providing most of its functionalities, trigger fsck automatic HDD check on next reboot, reboot, check what is going on and monitor the machine from there on.

Hopefully the few described steps, has helped some sysadmin. There is plenty of things which I've described that might go wrong, even following the described steps, might not help if the machines Storage Drives / SAS / SSD has too much of a damage. But as said in most cases following this few steps would improve the machine state.

Wish you the best of luck!

 

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Posted in Linux, Performance Tuning, Remote System Administration, System Administration, System Optimization, Various | No Comments »

How to check if network ethernet cards are active on Linux server / detect the physical connected state of a network cable / connector?

Tuesday, November 1st, 2022

linux-check-connectivity-interface-software-implementation-of-multi-queue-support-in-Linux-using-commodity-Ethernet-NICs

Lets say you are administrating some Linux server and need to upgrade a switch and temporary move out traffic for ethernet interfaces connected via a Gigabit network to a Gigabit Cisco / Junper EX Series / HPE Aruba or Arista Platform network switch to a newer version of a switch or software.

Usually if you don't have control over the Network switch (if you're employeed in a large corporation), that migration will be handled by a colleague from the Network team in a prescheduled time slot and usually in a coordinated meeting, once the cabling is being physically moved by someone a person in the Computer Room (in DC) in the respective data center.

Then once the correct commands are executed on the network switch to remap the new cable to point to the right location on the Linux server, where the old switch was and the setup has to be double verified by the network team mate.

Once this is done either by a colleague or if you're in a smaller company and you work as one man army sysadmin and you have done it yourself.
Next step is to verify that the Ethernet LAN cards on the Linux server lets say 6 or 8 LAN cards are still connected and active to the preset Active LAN / VLANs.

On Linux this is pretty simple and there is many ways to do it with external tools like ethtool, if you're lucky and your server doesn't have to have a paranoid security rules to follow or have to be a minimilastic machine with a 100% PCI High security standards compliancy.

To check connectivity for all your ethernet interfaces you can simply run a one liner shell script like so:

[root@linux-server ~]# for i in $(ip a s|grep -i :|grep -v link|awk '{ print $2 }'|sed -e 's#:##g'|grep -v lo); do ethtool $i; done
Settings for eth0:
        Link detected: yes
Settings for eth1:
        Link detected: yes
Settings for eth2:
        Link detected: yes

So far so good but what if your RHEL / CentOS / Debian server doesn't have ethtool installed and you're not allowed to install it then how can you check whether network cable connector is indicating a network activity to the connected Ethernet LAN cards?

[root@linux-server ~]# for f in $(ls -1 /sys/class/net/); do echo "Eth inface: $f"; cat /sys/class/net/$f/operstate; done
Eth inface: eth0
up
Eth inface: eth1
up
Eth inface: eth2
up
Eth inface: lo
unknown

If your operstate returns something different like state unknown, e.g.:

root@linux-server ~]# cd /sys/class/net/
[root@linux-server net]# grep "" eth2/operstate
unknown
[root@linux-server net]#

[root@linux-server net]# grep "" eth{0,1,2,3}/operstate  
eth0/operstate:unknown
eth1/operstate:unknown
eth2/operstate:unknown
eth3/operstate:unknown

Then you need to check the carrier file

[root@linux-server net]# grep "" eth{0,1,2,3}/carrier
eth0/carrier:1
eth1/carrier:1
eth2/carrier:1
eth3/carrier:1

It could return either 0 or 1

The number 1 in the above output means that the network cable is physically connected to your network card’s slot meaning your network switch migration is success.

Method 2: Next, we will test a second network interface eth1:

[root@linux-server net]# cat /sys/class/net/eth1/carrier
[root@linux-server net]# cat: /sys/class/net/eth1/carrier: Invalid argument

This command’s output most likely means the the eth1 network interface is in powered down state.

So what have learned?

We have learned how to monitor the state of the network cable connected to a Linux ethernet device via external switch that is migrated without the use of any external tools like ethtool.

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Posted in Linux, System Administration | No Comments »

Enable zabbix agent to work with SeLinux enabled on CentOS 7 Linux

Wednesday, October 19th, 2022

If you have the task to install and use zabbix-agent or zabbix-proxy to report to zabbix-server on CentOS 7 with enabled SeLinux services for security reasons and you have no mean to disable the selinux which is a common step to take under this circumstances, you will have to add the zabbix services to be exluded as permissive in selinux. In below article I'll show you how this is done in few easy steps.

zabbix-agent-service-selinux-linux-real-time-operating-sytems

 

1. Check the system sestatus

[root@linux zabbix]# sestatus
SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   enforcing
Mode from config file:          enforcing
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Max kernel policy version:      28


2. Enable zabbix to be permissive in selinux

To be able to set zabbix to be in permissive mode as well as for further troubleshooting if you have to enable other  linux services inside selinux you have to install below RPM packs.

[root@linux zabbix]# yum install setroubleshoot.x86_64 setools.x86_64 setools-console.x86_64 policycoreutils-python.x86_64

Set the zabbix permissive exclude rule in SeLINUX

[root@linux zabbix]# semanage permissive –add zabbix_t

Re-run the zabbix proxy (if you have a local zabbix-proxy running and the zabbix-agent)

[root@linux zabbix]# systemctl start zabbix-proxy.service

[root@linux zabbix]# systemctl start zabbix-agent.service

[root@linux zabbix]# systemctl status zabbix-agent
● zabbix-agent.service – Zabbix Agent
   Loaded: loaded (/usr/lib/systemd/system/zabbix-agent.service; enabled; vendor preset: disabled)
   Active: active (running) since Tue 2022-10-18 09:30:16 CEST; 1 day 7h ago
 Main PID: 962952 (zabbix_agentd)
    Tasks: 6 (limit: 100884)
   Memory: 5.1M
   CGroup: /system.slice/zabbix-agent.service
           ├─962952 /usr/sbin/zabbix_agentd -c /etc/zabbix/zabbix_agentd.conf
           ├─962955 /usr/sbin/zabbix_agentd: collector [idle 1 sec]
           ├─962956 /usr/sbin/zabbix_agentd: listener #1 [waiting for connection]
           ├─962957 /usr/sbin/zabbix_agentd: listener #2 [waiting for connection]
           ├─962958 /usr/sbin/zabbix_agentd: listener #3 [waiting for connection]
           └─962959 /usr/sbin/zabbix_agentd: active checks #1 [idle 1 sec]

Oct 18 09:30:16 linux systemd[1]: Starting Zabbix Agent…
Oct 18 09:30:16 linux systemd[1]: Started Zabbix Agent.

3. Check inside audit logs all is OK

To make sure zabbix is really enabled to be omitted by selinux rules check audit.log

[root@linux zabbix]# grep zabbix_proxy /var/log/audit/audit.log

That's all folks, Enjoy ! 🙂

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Posted in Migration, System Administration, Zabbix | No Comments »

How to install Viber client on Debian GNU / Linux / Ubuntu / Mint in 2022 and enable Bulgarian language cyrillic phonetic keyboard

Tuesday, October 4th, 2022

How to install Viber client on Debian GNU / Linux / Ubuntu / Mint in 2022 and enable Bulgarian language cyrillic phonetic keyboard

how-to-install-and-use-viber-on-gnu-linux-desktop-viber-logo-tux-for-audio-video-communication-with-nonfree-world

So far I've always used Viber on my mobile phone earlier on my Blu H1 HD and now after my dear friend Nomen give me his old iPhone X, i have switched to the iOS version which i find still a bit strangely looking.
Using Viber on the phone and stretching for the Phone all day long is really annoying especially if you work in the field of Information technology like me as System Administrator programmer. Thus having a copy of Viber on your Linux desktop that is next to you is a must.
Viber is proprietary software on M$ Windows its installation is a piece of cake, you install confirm that you want to use it on a secondary device by scanning the QR and opening the URL with your phone and you're ready to Chat and Viber Call with your friends or colleagues. 

As often on Linux, it is a bit more complicated as the developers of Viber, perhaps did not put too much effort to port it to Linux or did not have much knowledge of how Linux is organized or they simply did not have the time to put for enough testing, and hence installing the Viber on Linux does not straight supported the Bulgarian traditional cyrillic. I've done some small experimentation and installed Viber on Linux both as inidividual package from their official Linux .deb package as well as of a custom build flatpak. In this small article, i'll put it down how i completed that as well as how managed to workaround the language layout problems with a simple setxkbmap cmd.

How to install Viber client on Debian GNU / Linux / Ubuntu / Mint in 2022 and enable Bulgarian language cyrillic phonetic

1.Install and use Viber as a standard Desktop user Linux application

Download latest Debian AMD64 .deb binary from official Viber website inside some dir with Opera / Chrome / Firefox browser and store it in:

hipo@jericho: ~$ cd /usr/local/src

Alternatively you can run the above wget command, but this is not the recommended way since you might end up with Viber Linux version that is older.

hipo@jericho: ~$ sudo wget http://download.cdn.viber.com/cdn/desktop/Linux/viber.deb
hipo@jericho: ~$ su – root

1.2. Resolve the required Viber .deb package dependecies

To resolve the required dependencies of viber.deb package, easiest way is to use gdebi-core # apt-cache show gdebi-core|grep Description-en -A4 Description-en: simple tool to install deb files  gdebi lets you install local deb packages resolving and installing  its dependencies. apt does the same, but only for remote (http, ftp)  located packages. # apt-get install gdebi-core … # apt-get install -f ./viber …

1.3. Setting the default language for Viber to support non-latin languages like Cyrillic

I'm Bulgarian and I use the Phonetic Traidional BG keyboard that is UTF8 compatible but cyrillic and non latin. However Viber developers seems to not put much effort and resolve that the Bulgarian Phonetic Traditional keyboard added in my Mate Desktop Environment to work out of the box with Viber on Linux. So as usual in Linux you need a hack ! The hack consists of using setxkbmap to set supported keyboard layouts for Viber US,BG and Traditional Phonetic. This can be done with above command:

setxkbmap -layout 'us,bg' -variant ' ,phonetic' -option 'grp:lalt_lshift_toggle'

To run it everytime together with the Viber binary executable that is stored in location /opt/viber/Viber as prepared by the package developer by install and post-install scripts in the viber.deb, prepared also a 3 liner tine script:

# cat start_viber.sh
#!/bin/bash
cd /opt/viber; setxkbmap -layout 'us,bg' -variant ' ,phonetic' -option 'grp:lalt_lshift_toggle'
./Viber


viber-appearance-menu-screenshot-linux


2. Install Viber in separated isolated sandbox from wider system

Second way if you don't trust a priorietary third party binary of Viber (and don't want for Viber to be able to possibly read data of your login GNOME / KDE user, e.g. not be spied by KGB 🙂

For those curious why i'm saying that Viber is mostly used mainly in the ex Soviet Union and in the countries that used to be Soviet satellite ones for one or another reason and though being developed in Israel some of its development in the past was done in Belarus as far as I remember one of the main 3 members (Ukraine, Belarus and Russia) that took the decision to dissolve the USSR 🙂

Talking about privacy if you're really concerned about privacy the best practice is not to use neither WhatApp nor Viber at all on any OS, but this is hard as usually most people are already "educated" to use one of the two. 
For the enthusiasts however I do recommend just to use the Viber / WhatsApp free GPLed software alternative for Vital communication that you don't want to have been listened to by the China / USA / Russia etc. 
Such a good free software alternative is Jitsy and it has both a Web interface that can be used very easily straight inside a browser or you could install a desktop version for PC / iOS and Android and more.
An interesting and proud fact to mention about Jitsy is that its main development that led the project to the state it is now is being done by a buddy Bulgarian ! Good Job man ! 🙂

If you want to give jitsy a try in web with a friend just clik over my pc-freak home lab machine has installed usable version on meet.pc-freak.net

In the same way people in most countries with American and English free world use the WhatsApp which is a another free spy and self analysis software offered by America most likely collecting your chat data and info about you in the (US Central Intelligence Agency) CIA databases. But enough blant so to minimize a bit the security risks of having the binary run directly as a process you can use a containerization like docker to run it inside and isolate from the rest of your Linux desktop. flatpak is a tool developed exactly for that.

 

hipo@jeremiah:/opt/viber$ apt-cache show flatpak|grep -i Description-en -A 13

Description-en: Application deployment framework for desktop apps
 Flatpak installs, manages and runs sandboxed desktop application bundles.
 Application bundles run partially isolated from the wider system, using
 containerization techniques such as namespaces to prevent direct access
 to system resources. Resources from outside the sandbox can be accessed
 via "portal" services, which are responsible for access control; for
 example, the Documents portal displays an "Open" dialog outside the
 sandbox, then allows the application to access only the selected file.
 .
 Each application uses a specified "runtime", or set of libraries, which is
 available as /usr inside its sandbox. This can be used to run application
 bundles with multiple, potentially incompatible sets of dependencies within
 the same desktop environment.

Having Viber installed on Linux inside a container with flatpak is as simple as to adding, repository and installing the flatpak package
already bundled and stored inside flathub repository, e.g.:
 

2.1. Install flatpak 

# sudo apt install flatpak


flatpak-viber-installation-linux-screenshot
 

2.2. Add flathub install repository

flatpak is pretty much like dockerhub, it contains images of containered sandbox copies of software, the main advantage of flatpak is its portability, scalability and security.
Of course if you're a complete security freak you can prepare yourself an own set of Viber and add it to flathub and use instead of the original one 🙂
 

# sudo flatpak remote-add –if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

2.3. Install Flatpak-ed Viber 

#sudo flatpak install flathub com.viber.Viber

 

Reboot the PC and to test Viber will run containerized normally issue below flapak start command:

# /usr/bin/flatpak run –branch=stable –arch=x86_64 –command=viber com.viber.Viber

 

Viber-inside-flatpak-sandbox-on-debian-linux-screenshot-running

! NOTE !  The Linux version of Viber is missing Backups options, exclusively the Settings -> Account -> Viber backup menus is missing, but the good news is that if you're using the Viber client
as a secondary device message client, on first login you'll be offered to Synchronize your Viber data with your 1st Active device (usually your Smart Phone). Just click on it and allow the synchronization from your phone and in a while the Contacts and message history should be on the Linux Viber client.

That's it Enjoy your Viber Sound and Video on Linux ! 🙂

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Posted in Linux, Linux and FreeBSD Desktop, Linux Audio & Video, Video Streaming | No Comments »

Install Zabbix Agent client on CentOS 9 Stream Linux, Disable Selinux and Firewalld on CentOS9 to make zabbix-agentd send data to server

Thursday, April 14th, 2022

https://pc-freak.net/images/zabbix_agent_active_passive-zabbix-agent-centos-9-install-howto

Installing Zabbix is usually a trivial stuff, you either use the embedded distribution built packages if such are available this is for example defetch the right zabbix release repository  that configures the Zabbix official repo in the system, configure the Zabbix server or Proxy if such is used inside /etc/zabbix/zabbix_agentd.conf and start the client, i.e. I expected that it will be a simple and straight forward also on the freshly installed CentOS 9 Linux cause placing a zabbix-agent monitroing is a trivial stuff however installing came to error:

Key import failed (code 2). Failing package is: zabbix-agent-6.0.3-1.el8.x86_64

 

This is what I've done

1. Download and install zabbix-release-6.0-1.el8.noarch.rpm directly from zabbix

I've followed the official documentation from zabbix.com and ran:
 

[root@centos9 /root ]# rpm -Uvh https://repo.zabbix.com/zabbix/6.0/rhel/8/x86_64/zabbix-release-6.0-1.el8.noarch.rpm

…


2. Install  the zabbix-agent RPM package from the repositry

[root@centos9 rpm-gpg]# yum install zabbix-agent -y
Last metadata expiration check: 0:02:46 ago on Tue 12 Apr 2022 08:49:34 AM EDT.
Dependencies resolved.
=============================================
 Package                               Architecture                Version                              Repository                      Size
=============================================
Installing:
 zabbix-agent                          x86_64                      6.0.3-1.el8                          zabbix                         526 k
Installing dependencies:
 compat-openssl11                      x86_64                      1:1.1.1k-3.el9                       appstream                      1.5 M
 openldap-compat                       x86_64                      2.4.59-4.el9                         baseos                          14 k

Transaction Summary
==============================================
Install  3 PackagesTotal size: 2.0 M
Installed size: 6.1 M
Downloading Packages:
[SKIPPED] openldap-compat-2.4.59-4.el9.x86_64.rpm: Already downloaded
[SKIPPED] compat-openssl11-1.1.1k-3.el9.x86_64.rpm: Already downloaded
[SKIPPED] zabbix-agent-6.0.3-1.el8.x86_64.rpm: Already downloaded
Zabbix Official Repository – x86_64                                                                          1.6 MB/s | 1.7 kB     00:00
Importing GPG key 0xA14FE591:
 Userid     : "Zabbix LLC <packager@zabbix.com>"
 Fingerprint: A184 8F53 52D0 22B9 471D 83D0 082A B56B A14F E591
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-ZABBIX-A14FE591
Key import failed (code 2). Failing package is: zabbix-agent-6.0.3-1.el8.x86_64
 GPG Keys are configured as: file:///etc/pki/rpm-gpg/RPM-GPG-KEY-ZABBIX-A14FE591
The downloaded packages were saved in cache until the next successful transaction.
You can remove cached packages by e
xecuting 'yum clean packages'.
Error: GPG check FAILED


3. Work around to skip GPG to install zabbix-agent 6 on CentOS 9

With Linux everything becomes more and more of a hack …
The logical thing to was to first,  check and it assure that the missing RPM GPG key is at place

[root@centos9 rpm-gpg]# ls -al  /etc/pki/rpm-gpg/RPM-GPG-KEY-ZABBIX-A14FE591
-rw-r–r– 1 root root 1719 Feb 11 16:29 /etc/pki/rpm-gpg/RPM-GPG-KEY-ZABBIX-A14FE591

Strangely the key was in place.

Hence to have the key loaded I've tried to import the gpg key manually with gpg command:

[root@centos9 rpm-gpg]# gpg –import /etc/pki/rpm-gpg/RPM-GPG-KEY-ZABBIX-A14FE591


And attempted install again zabbix-agent once again:
 

[root@centos9 rpm-gpg]# yum install zabbix-agent -y
Last metadata expiration check: 0:02:46 ago on Tue 12 Apr 2022 08:49:34 AM EDT.
Dependencies resolved.
==============================================
 Package                               Architecture                Version                              Repository                      Size
==============================================
Installing:
 zabbix-agent                          x86_64                      6.0.3-1.el8                          zabbix                         526 k
Installing dependencies:
 compat-openssl11                      x86_64                      1:1.1.1k-3.el9                       appstream                      1.5 M
 openldap-compat                       x86_64                      2.4.59-4.el9                         baseos                          14 k

Transaction Summary
==============================================
Install  3 Packages

Total size: 2.0 M
Installed size: 6.1 M
Downloading Packages:
[SKIPPED] openldap-compat-2.4.59-4.el9.x86_64.rpm: Already downloaded
[SKIPPED] compat-openssl11-1.1.1k-3.el9.x86_64.rpm: Already downloaded
[SKIPPED] zabbix-agent-6.0.3-1.el8.x86_64.rpm: Already downloaded
Zabbix Official Repository – x86_64                                                                          1.6 MB/s | 1.7 kB     00:00
Importing GPG key 0xA14FE591:
 Userid     : "Zabbix LLC <packager@zabbix.com>"
 Fingerprint: A184 8F53 52D0 22B9 471D 83D0 082A B56B A14F E591
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-ZABBIX-A14FE591
Key import failed (code 2). Failing package is: zabbix-agent-6.0.3-1.el8.x86_64
 GPG Keys are configured as: file:///etc/pki/rpm-gpg/RPM-GPG-KEY-ZABBIX-A14FE591
The downloaded packages were saved in cache until the next successful transaction.
You can remove cached packages by executing 'yum clean packages'.
Error: GPG check FAILED


Unfortunately that was not a go, so totally pissed off I've disabled the gpgcheck for packages completely as a very raw bad and unrecommended work-around to eventually install the zabbix-agentd like that.

Usually the RPM gpg key failures check on RPM packages could be could be workaround with in dnf, so I've tried that one without success.

[root@centos9 rpm-gpg]# dnf update –nogpgcheck
Total                                                                                                        181 kB/s | 526 kB     00:02
Zabbix Official Repository – x86_64                                                                          1.6 MB/s | 1.7 kB     00:00
Importing GPG key 0xA14FE591:
 Userid     : "Zabbix LLC <packager@zabbix.com>"
 Fingerprint: A184 8F53 52D0 22B9 471D 83D0 082A B56B A14F E591
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-ZABBIX-A14FE591
Is this ok [y/N]: y
Key import failed (code 2). Failing package is: zabbix-agent-6.0.3-1.el8.x86_64
 GPG Keys are configured as: file:///etc/pki/rpm-gpg/RPM-GPG-KEY-ZABBIX-A14FE591
The downloaded packages were saved in cache until the next successful transaction.
You can remove cached packages by executing 'dnf clean packages'.
Error: GPG check FAILED

Further tried to use the –nogpgpcheck 
which according to its man page:


–nogpgpcheck 
Skip checking GPG signatures on packages (if RPM policy allows).


In yum the nogpgcheck option according to its man yum does exactly the same thing


[root@centos9 rpm-gpg]# yum install zabbix-agent –nogpgcheck -y
 

Dependencies resolved.
===============================================
 Package                             Architecture                  Version                               Repository                     Size
===============================================
Installing:
 zabbix-agent                        x86_64                        6.0.3-1.el8                           zabbix                        526 k

Transaction Summary
===============================================

Total size: 526 k
Installed size: 2.3 M
Is this ok [y/N]: y
Downloading Packages:
…
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                                                                     1/1
  Running scriptlet: zabbix-agent-6.0.3-1.el8.x86_64                                                                                     1/2
  Reinstalling     : zabbix-agent-6.0.3-1.el8.x86_64                                                                                     1/2
  Running scriptlet: zabbix-agent-6.0.3-1.el8.x86_64                                                                                     1/2
  Running scriptlet: zabbix-agent-6.0.3-1.el8.x86_64                                                                                     2/2
  Cleanup          : zabbix-agent-6.0.3-1.el8.x86_64                                                                                     2/2
  Running scriptlet: zabbix-agent-6.0.3-1.el8.x86_64                                                                                     2/2
  Verifying        : zabbix-agent-6.0.3-1.el8.x86_64                                                                                     1/2
  Verifying        : zabbix-agent-6.0.3-1.el8.x86_64                                                                                     2/2

Installed:
  zabbix-agent-6.0.3-1.el8.x86_64

Complete!
[root@centos9 ~]#

Voila! zabbix-agentd on CentOS 9 Install succeeded!

Yes I know disabling a GPG check is not really secure and seems to be an ugly solution but since I'm cut of time in the moment and it is just for experimental install of zabbix-agent on CentOS
plus we already trusted the zabbix package repository anyways, I guess it doesn't much matter.

4. Configure Zabbix-agent on the machine

Once you choose how the zabbix-agent should sent the data to the zabbix-server (e.g. Active or Passive) mode the The minimum set of configuration you should
have at place should be something like mine:

[root@centos9 ~]# grep -v '\#' /etc/zabbix/zabbix_agentd.conf | sed /^$/d
PidFile=/var/run/zabbix/zabbix_agentd.pid
LogFile=/var/log/zabbix/zabbix_agentd.log
LogFileSize=0
Server=192.168.1.70,127.0.0.1
ServerActive=192.168.1.70,127.0.0.1
Hostname=centos9
Include=/etc/zabbix/zabbix_agentd.d/*.conf

5. Start and Enable zabbix-agent client

To have it up and running

[root@centos9 ~]# systemct start zabbix-agent
[root@centos9 ~]# systemctl enable zabbix-agent

6. Disable SELinux to prevent it interfere with zabbix-agentd 

Other amazement was that even though I've now had configured Active check and a Server and correct configuration the Zabbix-Server could not reach the zabbix-agent for some weird reason.
I thought that it might be selinux and checked it and seems by default in the fresh installed CentOS 9 Linux selinux is already automatically set to enabled.

After stopping it i made sure, SeLinux would block for security reasons client connectivity to the zabbix-server until you either allow zabbix exception in SeLinux or until completely disable it.
 

[root@centos9 ~]# sestatus

SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   enforcing
Mode from config file:          enforcing
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Memory protection checking:     actual (secure)
Max kernel policy version:      31

To temporarily change the mode from its default targeted to permissive mode 

[root@centos9 ~]# setenforce 0

[root@centos9 ~]# sestatus

SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   permissive
Mode from config file:          permissive
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Memory protection checking:     actual (secure)
Max kernel policy version:      31


That would work for current session but won't take affect on next reboot, thus it is much better to disable selinux on next boot:

[root@centos9 ~]# cat /etc/selinux/config
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing – SELinux security policy is enforced.
#     permissive – SELinux prints warnings instead of enforcing.
#     disabled – No SELinux policy is loaded.
SELINUX=permissive
# SELINUXTYPE= can take one of these three values:
#     targeted – Targeted processes are protected,
#     minimum – Modification of targeted policy. Only selected processes are protected. 
#     mls – Multi Level Security protection.
SELINUXTYPE=targeted

 

To disable selinux change:

SELINUXTYPE=disabled

[root@centos9 ~]# grep -v \# /etc/selinux/config

SELINUX=disabled
SELINUXTYPE=targeted


To make the OS disable selinux and test it is disabled you will have to reboot 

[root@centos9 ~]# reboot


Check its status again, it should be:

[root@centos9 ~]# sestatus
SELinux status:                 disabled


7. Enable zabbix-agent through firewall or disable firewalld service completely

By default CentOS 9 has the firewalld also enabled and either you have to enable zabbix to communicate to the remote server host.

To enable access for from and to zabbix-agentd in both Active / Passive mode:

#firewall settings:
[root@centos9 rpm-gpg]# firewall-cmd –permanent –add-port=10050/tcp
[root@centos9 rpm-gpg]# firewall-cmd –permanent –add-port=10051/tcp
[root@centos9 rpm-gpg]# firewall-cmd –reload
[root@centos9 rpm-gpg]# systemctl restart firewalld
[root@centos9 rpm-gpg]# systemctl restart zabbix-agent


If the machine is in a local DMZ-ed network with tightly configured firewall router in front of it, you could completely disable firewalld.

[root@centos9 rpm-gpg]# systemctl stop firewalld
[root@centos9 rpm-gpg]# systemctl disable firewalld
Removed /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.

 

Next login to Zabbix-server web interface with administrator and from Configuration -> Hosts -> Create the centos9 hostname and add it a template of choice. The data from the added machine should shortly appear after another zabbix restart:

[root@centos9 rpm-gpg]#  systemctl restart zabbix-agentd


8. Tracking other oddities with the zabbix-agent through log

If anyways still zabbix have issues connectin to remote node, increase the debug log level section
 

[root@centos9 rpm-gpg]# vim /etc/zabbix/zabbix_agentd.conf
DebugLevel 5

### Option: DebugLevel
#       Specifies debug level:
#       0 – basic information about starting and stopping of Zabbix processes
#       1 – critical information
#       2 – error information
#       3 – warnings
#       4 – for debugging (produces lots of information)
#       5 – extended debugging (produces even more information)
#
# Mandatory: no
# Range: 0-5
# Default:
# DebugLevel=3

[root@centos9 rpm-gpg]# systemctl restart zabbix-agent

Keep in mind that debugging will be too verbose, so once you make the machine being seen in zabbix, don't forget to comment out the line and restart agent to turn it off.

9. Testing zabbix-agent, How to send an alert to specific item key

Usually when writting userparameter scripts, data collected from scripts is being sent to zabbix serveria via Item keys.
Thus one way to check the zabbix-agent -> zabbix server data send works fine is to send some simultaneous data via a key
Once zabbix-agent is configured on the machine 

In this case we will use something like ApplicationSupport-Item as an item.
 

[root@centos9 rpm-gpg]# /usr/bin/zabbix_sender -c "/etc/zabbix/zabbix_agentd.conf" -k "ApplicationSupport-Item" -o "here is the message"

Assuming you have created the newly prepared zabbix-agent host into Zabbix Server, you should be shortly able to see the data come in Latest data.

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Posted in CentOS, Linux, Monitoring, Zabbix | No Comments »

Create Linux High Availability Load Balancer Cluster with Keepalived and Haproxy on Linux

Tuesday, March 15th, 2022

keepalived-logo-linux

Configuring a Linux HA (High Availibiltiy) for an Application with Haproxy is already used across many Websites on the Internet and serious corporations that has a crucial infrastructure has long time
adopted and used keepalived to provide High Availability Application level Clustering.
Usually companies choose to use HA Clusters with Haproxy with Pacemaker and Corosync cluster tools.
However one common used alternative solution if you don't have the oportunity to bring up a High availability cluster with Pacemaker / Corosync / pcs (Pacemaker Configuration System) due to fact machines you need to configure the cluster on are not Physical but VMWare Virtual Machines which couldn't not have configured a separate Admin Lans and Heartbeat Lan as we usually do on a Pacemaker Cluster due to the fact the 5 Ethernet LAN Card Interfaces of the VMWare Hypervisor hosts are configured as a BOND (e.g. all the incoming traffic to the VMWare vSphere  HV is received on one Virtual Bond interface).

I assume you have 2 separate vSphere Hypervisor Physical Machines in separate Racks and separate switches hosting the two VMs.
For the article, I'll call the two brand new brought Virtual Machines with some installation automation software such as Terraform or Ansible – vm-server1 and vm-server2 which would have configured some recent version of Linux.

In that scenario to have a High Avaiability for the VMs on Application level and assure at least one of the two is available at a time if one gets broken due toe malfunction of the HV, a Network connectivity issue, or because the VM OS has crashed.
Then one relatively easily solution is to use keepalived and configurea single High Availability Virtual IP (VIP) Address, i.e. 10.10.10.1, which would float among two VMs using keepalived so at a time at least one of the two VMs would be reachable on the Network.

haproxy_keepalived-vip-ip-diagram-linux

Having a VIP IP is quite a common solution in corporate world, as it makes it pretty easy to add F5 Load Balancer in front of the keepalived cluster setup to have a 3 Level of security isolation, which usually consists of:

1. Physical (access to the hardware or Virtualization hosts)
2. System Access (The mechanism to access the system login credetials users / passes, proxies, entry servers leading to DMZ-ed network)
3. Application Level (access to different programs behind L2 and data based on the specific identity of the individual user,
special Secondary UserID,  Factor authentication, biometrics etc.)
 

1. Install keepalived and haproxy on machines

Depending on the type of Linux OS:

On both machines
 

[root@server1:~]# yum install -y keepalived haproxy
…

If you have to install keepalived / haproxy on Debian / Ubuntu and other Deb based Linux distros

[root@server1:~]# apt install keepalived haproxy –yes
…

2. Configure haproxy (haproxy.cfg) on both server1 and server2

 

Create some /etc/haproxy/haproxy.cfg configuration

 

[root@server1:~]# vim /etc/haproxy/haproxy.cfg

#———————————————————————
# Global settings
#———————————————————————
global
    log          127.0.0.1 local6 debug
    chroot       /var/lib/haproxy
    pidfile      /run/haproxy.pid
    stats socket /var/lib/haproxy/haproxy.sock mode 0600 level admin 
    maxconn      4000
    user         haproxy
    group        haproxy
    daemon
    #debug
    #quiet

#———————————————————————
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#———————————————————————
defaults
    mode        tcp
    log         global
#    option      dontlognull
#    option      httpclose
#    option      httplog
#    option      forwardfor
    option      redispatch
    option      log-health-checks
    timeout connect 10000 # default 10 second time out if a backend is not found
    timeout client 300000
    timeout server 300000
    maxconn     60000
    retries     3

#———————————————————————
# round robin balancing between the various backends
#———————————————————————

listen FRONTEND_APPNAME1
        bind 10.10.10.1:15000
        mode tcp
        option tcplog
#        #log global
        log-format [%t]\ %ci:%cp\ %bi:%bp\ %b/%s:%sp\ %Tw/%Tc/%Tt\ %B\ %ts\ %ac/%fc/%bc/%sc/%rc\ %sq/%bq
        balance roundrobin
        timeout client 350000
        timeout server 350000
        timeout connect 35000
        server app-server1 10.10.10.55:30000 weight 1 check port 68888
        server app-server2 10.10.10.55:30000 weight 2 check port 68888

listen FRONTEND_APPNAME2
        bind 10.10.10.1:15000
        mode tcp
        option tcplog
        #log global
        log-format [%t]\ %ci:%cp\ %bi:%bp\ %b/%s:%sp\ %Tw/%Tc/%Tt\ %B\ %ts\ %ac/%fc/%bc/%sc/%rc\ %sq/%bq
        balance roundrobin
        timeout client 350000
        timeout server 350000
        timeout connect 35000
        server app-server1 10.10.10.55:30000 weight 5
        server app-server2 10.10.10.55:30000 weight 5 

 

You can get a copy of above haproxy.cfg configuration here.
Once configured roll it on.

[root@server1:~]#  systemctl start haproxy
 [root@server1:~]# ps -ef|grep -i hapro
root      285047       1  0 Mar07 ?        00:00:00 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid
haproxy   285050  285047  0 Mar07 ?        00:00:26 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid

Bring up the haproxy also on server2 machine, by placing same configuration and starting up the proxy.
 

[root@server1:~]# vim /etc/haproxy/haproxy.cfg
…

…

 

3. Configure keepalived on both servers

We'll be configuring 2 nodes with keepalived even though if necessery this can be easily extended and you can add more nodes.
First we make a copy of the original or existing server configuration keepalived.conf (just in case we need it later on or if you already had something other configured manually by someone – that could be so on inherited servers by other sysadmin)
 

[root@server1:~]# mv /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.orig
[root@server2:~]# mv /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.orig

a. Configure keepalived to serve as a MASTER Node

 

[root@server1:~]# vim /etc/keepalived/keepalived.conf

Master Node
global_defs {
  router_id server1-fqdn # The hostname of this host.
  
  enable_script_security
  # Synchro of the state of the connections between the LBs on the eth0 interface
   lvs_sync_daemon eth0
 
notification_email {
        linuxadmin@notify-domain.com     # Email address for notifications 
    }
 notification_email_from keepalived@server1-fqdn        # The from address for the notifications
    smtp_server 127.0.0.1                       # SMTP server address
    smtp_connect_timeout 15
}

vrrp_script haproxy {
  script "killall -0 haproxy"
  interval 2
  weight 2
  user root
}

vrrp_instance LB_VIP_QA {
  virtual_router_id 50
  advert_int 1
  priority 51

  state MASTER
  interface eth0
  smtp_alert          # Enable Notifications Via Email
  
  authentication {
              auth_type PASS
              auth_pass testp141

    }
### Commented because running on VM on VMWare
##    unicast_src_ip 10.44.192.134 # Private IP address of master
##    unicast_peer {
##        10.44.192.135           # Private IP address of the backup haproxy
##   }

#        }
# master node with higher priority preferred node for Virtual IP if both keepalived up
###  priority 51
###  state MASTER
###  interface eth0
  virtual_ipaddress {
     10.10.10.1 dev eth0 # The virtual IP address that will be shared between MASTER and BACKUP
  }
  track_script {
      haproxy
  }
}
 

 To dowload a copy of the Master keepalived.conf configuration click here

Below are few interesting configuration variables, worthy to mention few words on, most of them are obvious by their names but for more clarity I'll also give a list here with short description of each:

 

  • vrrp_instance – defines an individual instance of the VRRP protocol running on an interface.
  • state – defines the initial state that the instance should start in (i.e. MASTER / SLAVE )state –
  • interface – defines the interface that VRRP runs on.
  • virtual_router_id – should be unique value per Keepalived Node (otherwise slave master won't function properly)
  • priority – the advertised priority, the higher the priority the more important the respective configured keepalived node is.
  • advert_int – specifies the frequency that advertisements are sent at (1 second, in this case).
  • authentication – specifies the information necessary for servers participating in VRRP to authenticate with each other. In this case, a simple password is defined.
    only the first eight (8) characters will be used as described in  to note is Important thing
    man keepalived.conf – keepalived.conf variables documentation !!! Nota Bene !!! – Password set on each node should match for nodes to be able to authenticate !
  • virtual_ipaddress – defines the IP addresses (there can be multiple) that VRRP is responsible for.
  • notification_email – the notification email to which Alerts will be send in case if keepalived on 1 node is stopped (e.g. the MASTER node switches from host 1 to 2)
  • notification_email_from – email address sender from where email will originte
    ! NB ! In order for notification_email to be working you need to have configured MTA or Mail Relay (set to local MTA) to another SMTP – e.g. have configured something like Postfix, Qmail or Postfix

b. Configure keepalived to serve as a SLAVE Node

[root@server1:~]# vim /etc/keepalived/keepalived.conf
 

#Slave keepalived
global_defs {
  router_id server2-fqdn # The hostname of this host!

  enable_script_security
  # Synchro of the state of the connections between the LBs on the eth0 interface
  lvs_sync_daemon eth0
 
notification_email {
        linuxadmin@notify-host.com     # Email address for notifications
    }
 notification_email_from keepalived@server2-fqdn        # The from address for the notifications
    smtp_server 127.0.0.1                       # SMTP server address
    smtp_connect_timeout 15
}

vrrp_script haproxy {
  script "killall -0 haproxy"
  interval 2
  weight 2
  user root
}

vrrp_instance LB_VIP_QA {
  virtual_router_id 50
  advert_int 1
  priority 50

  state BACKUP
  interface eth0
  smtp_alert          # Enable Notifications Via Email

authentication {
              auth_type PASS
              auth_pass testp141
}
### Commented because running on VM on VMWare    
##    unicast_src_ip 10.10.192.135 # Private IP address of master
##    unicast_peer {
##        10.10.192.134         # Private IP address of the backup haproxy
##   }

###  priority 50
###  state BACKUP
###  interface eth0
  virtual_ipaddress {
     10.10.10.1 dev eth0 # The virtual IP address that will be shared betwee MASTER and BACKUP.
  }
  track_script {
    haproxy
  }
}
 

Download the keepalived.conf slave config here

 

c. Set required sysctl parameters for haproxy to work as expected
 

[root@server1:~]# vim /etc/sysctl.conf
#Haproxy config
# haproxy
net.core.somaxconn=65535
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.ip_nonlocal_bind = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_max_syn_backlog = 10240
net.ipv4.tcp_max_tw_buckets = 400000
net.ipv4.tcp_max_orphans = 60000
net.ipv4.tcp_synack_retries = 3

4. Test Keepalived keepalived.conf configuration syntax is OK

 

[root@server1:~]# keepalived –config-test
(/etc/keepalived/keepalived.conf: Line 7) Unknown keyword 'lvs_sync_daemon_interface'
(/etc/keepalived/keepalived.conf: Line 21) Unable to set default user for vrrp script haproxy – removing
(/etc/keepalived/keepalived.conf: Line 31) (LB_VIP_QA) Specifying lvs_sync_daemon_interface against a vrrp is deprecated.
(/etc/keepalived/keepalived.conf: Line 31)              Please use global lvs_sync_daemon
(/etc/keepalived/keepalived.conf: Line 35) Truncating auth_pass to 8 characters
(/etc/keepalived/keepalived.conf: Line 50) (LB_VIP_QA) track script haproxy not found, ignoring…

I've experienced this error because first time I've configured keepalived, I did not mention the user with which the vrrp script haproxy should run,
in prior versions of keepalived, leaving the field empty did automatically assumed you have the user with which the vrrp script runs to be set to root
as of RHELs keepalived-2.1.5-6.el8.x86_64, i've been using however this is no longer so and thus in prior configuration as you can see I've
set the user in respective section to root.
The error Unknown keyword 'lvs_sync_daemon_interface' is also easily fixable by just substituting the lvs_sync_daemon_interface and lvs_sync_daemon and reloading
keepalived etc.

Once keepalived is started and you can see the process on both machines running in process list.

[root@server1:~]# ps -ef |grep -i keepalived
root     1190884       1  0 18:50 ?        00:00:00 /usr/sbin/keepalived -D
root     1190885 1190884  0 18:50 ?        00:00:00 /usr/sbin/keepalived -D

Next step is to check the keepalived statuses as well as /var/log/keepalived.log

If everything is configured as expected on both keepalived on first node you should see one is master and one is slave either in the status or the log

[root@server1:~]#systemctl restart keepalived

 

[root@server1:~]# systemctl status keepalived|grep -i state
Mar 14 18:59:02 server1-fqdn Keepalived_vrrp[1192003]: (LB_VIP_QA) Entering MASTER STATE

[root@server1:~]# systemctl status keepalived

● keepalived.service – LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; vendor preset: disabled)
   Active: inactive (dead) since Mon 2022-03-14 18:15:51 CET; 32min ago
  Process: 1187587 ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 1187589 (code=exited, status=0/SUCCESS)

Mar 14 18:15:04 server1lb-fqdn Keepalived_vrrp[1187590]: Sending gratuitous ARP on eth0 for 10.44.192.142
Mar 14 18:15:50 server1lb-fqdn systemd[1]: Stopping LVS and VRRP High Availability Monitor…
Mar 14 18:15:50 server1lb-fqdn Keepalived[1187589]: Stopping
Mar 14 18:15:50 server1lb-fqdn Keepalived_vrrp[1187590]: (LB_VIP_QA) sent 0 priority
Mar 14 18:15:50 server1lb-fqdn Keepalived_vrrp[1187590]: (LB_VIP_QA) removing VIPs.
Mar 14 18:15:51 server1lb-fqdn Keepalived_vrrp[1187590]: Stopped – used 0.002007 user time, 0.016303 system time
Mar 14 18:15:51 server1lb-fqdn Keepalived[1187589]: CPU usage (self/children) user: 0.000000/0.038715 system: 0.001061/0.166434
Mar 14 18:15:51 server1lb-fqdn Keepalived[1187589]: Stopped Keepalived v2.1.5 (07/13,2020)
Mar 14 18:15:51 server1lb-fqdn systemd[1]: keepalived.service: Succeeded.
Mar 14 18:15:51 server1lb-fqdn systemd[1]: Stopped LVS and VRRP High Availability Monitor

[root@server2:~]# systemctl status keepalived|grep -i state
Mar 14 18:59:02 server2-fqdn Keepalived_vrrp[297368]: (LB_VIP_QA) Entering BACKUP STATE

[root@server1:~]# grep -i state /var/log/keepalived.log
Mar 14 18:59:02 server1lb-fqdn Keepalived_vrrp[297368]: (LB_VIP_QA) Entering MASTER STATE
 

a. Fix Keepalived SECURITY VIOLATION – scripts are being executed but script_security not enabled.
 

When configurating keepalived for a first time we have faced the following strange error inside keepalived status inside keepalived.log 
 

Feb 23 14:28:41 server1 Keepalived_vrrp[945478]: SECURITY VIOLATION – scripts are being executed but script_security not enabled.

 

To fix keepalived SECURITY VIOLATION error:

Add to /etc/keepalived/keepalived.conf on the keepalived node hosts
inside 

global_defs {}

After chunk
 

enable_script_security

include

# Synchro of the state of the connections between the LBs on the eth0 interface
  lvs_sync_daemon_interface eth0

 

5. Prepare rsyslog configuration and Inlcude additional keepalived options
to force keepalived log into /var/log/keepalived.log

To force keepalived log into /var/log/keepalived.log on RHEL 8 / CentOS and other Redhat Package Manager (RPM) Linux distributions

[root@server1:~]# vim /etc/rsyslog.d/48_keepalived.conf

#2022/02/02: HAProxy logs to local6, save the messages
local7.*                                                /var/log/keepalived.log
if ($programname == 'Keepalived') then -/var/log/keepalived.log
if ($programname == 'Keepalived_vrrp') then -/var/log/keepalived.log
& stop

[root@server:~]# touch /var/log/keepalived.log

Reload rsyslog to load new config
 

[root@server:~]# systemctl restart rsyslog
[root@server:~]# systemctl status rsyslog
 

● rsyslog.service – System Logging Service
   Loaded: loaded (/usr/lib/systemd/system/rsyslog.service; enabled; vendor preset: enabled)
  Drop-In: /etc/systemd/system/rsyslog.service.d
           └─rsyslog-service.conf
   Active: active (running) since Mon 2022-03-07 13:34:38 CET; 1 weeks 0 days ago
     Docs: man:rsyslogd(8)
           https://www.rsyslog.com/doc/
 Main PID: 269574 (rsyslogd)
    Tasks: 6 (limit: 100914)
   Memory: 5.1M
   CGroup: /system.slice/rsyslog.service
           └─269574 /usr/sbin/rsyslogd -n

Mar 15 08:15:16 server1lb-fqdn rsyslogd[269574]: — MARK —
Mar 15 08:35:16 server1lb-fqdn rsyslogd[269574]: — MARK —
Mar 15 08:55:16 server1lb-fqdn rsyslogd[269574]: — MARK —

 

If once keepalived is loaded but you still have no log written inside /var/log/keepalived.log

[root@server1:~]# vim /etc/sysconfig/keepalived
 KEEPALIVED_OPTIONS="-D -S 7"

[root@server2:~]# vim /etc/sysconfig/keepalived
 KEEPALIVED_OPTIONS="-D -S 7"

[root@server1:~]# systemctl restart keepalived.service
[root@server1:~]#  systemctl status keepalived

● keepalived.service – LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; vendor preset: disabled)
   Active: active (running) since Thu 2022-02-24 12:12:20 CET; 2 weeks 4 days ago
 Main PID: 1030501 (keepalived)
    Tasks: 2 (limit: 100914)
   Memory: 1.8M
   CGroup: /system.slice/keepalived.service
           ├─1030501 /usr/sbin/keepalived -D
           └─1030502 /usr/sbin/keepalived -D

Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

[root@server2:~]# systemctl restart keepalived.service
[root@server2:~]# systemctl status keepalived
…

6. Monitoring VRRP traffic of the two keepaliveds with tcpdump
 

Once both keepalived are up and running a good thing is to check the VRRP protocol traffic keeps fluently on both machines.
Keepalived VRRP keeps communicating over the TCP / IP Port 112 thus you can simply snoop TCP tracffic on its protocol.
 

[root@server1:~]# tcpdump proto 112

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
11:08:07.356187 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:08.356297 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:09.356408 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:10.356511 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:11.356655 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20

[root@server2:~]# tcpdump proto 112

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
​listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
11:08:07.356187 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:08.356297 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:09.356408 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:10.356511 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:11.356655 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20

As you can see the VRRP traffic on the network is originating only from server1lb-fqdn, this is so because host server1lb-fqdn is the keepalived configured master node.

It is possible to spoof the password configured to authenticate between two nodes, thus if you're bringing up keepalived service cluster make sure your security is tight at best the machines should be in a special local LAN DMZ, do not configure DMZ on the internet !!! 🙂 Or if you eventually decide to configure keepalived in between remote hosts, make sure you somehow use encrypted VPN or SSH tunnels to tunnel the VRRP traffic.

[root@server1:~]# tcpdump proto 112 -vv
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
11:36:25.530772 IP (tos 0xc0, ttl 255, id 59838, offset 0, flags [none], proto VRRP (112), length 40)
    server1lb-fqdn > vrrp.mcast.net: vrrp server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20, addrs: VIPIP_QA auth "testp431"
11:36:26.530874 IP (tos 0xc0, ttl 255, id 59839, offset 0, flags [none], proto VRRP (112), length 40)
    server1lb-fqdn > vrrp.mcast.net: vrrp server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20, addrs: VIPIP_QA auth "testp431"

Lets also check what floating IP is configured on the machines:

[root@server1:~]# ip -brief address show
lo               UNKNOWN        127.0.0.1/8 
eth0             UP             10.10.10.5/26 10.10.10.1/32 

The 10.10.10.5 IP is the main IP set on LAN interface eth0, 10.10.10.1 is the floating IP which as you can see is currently set by keepalived to listen on first node.

[root@server2:~]# ip -brief address show |grep -i 10.10.10.1

An empty output is returned as floating IP is currently configured on server1

To double assure ourselves the IP is assigned on correct machine, lets ping it and check the IP assigned MAC  currently belongs to which machine.
 

[root@server2:~]# ping 10.10.10.1
PING 10.10.10.1 (10.10.10.1) 56(84) bytes of data.
64 bytes from 10.10.10.1: icmp_seq=1 ttl=64 time=0.526 ms
^C
— 10.10.10.1 ping statistics —
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.526/0.526/0.526/0.000 ms
[root@server2:~]# arp -an |grep -i 10.44.192.142
? (10.10.10.1) at 00:48:54:91:83:7d [ether] on eth0
[root@server2:~]# ip a s|grep -i 00:48:54:91:83:7d
[root@server2:~]# 

As you can see from below output MAC is not found in configured IPs on server2.
 

[root@server1-fqdn:~]# /sbin/ip a s|grep -i 00:48:54:91:83:7d -B1 -A1
 eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:48:54:91:83:7d brd ff:ff:ff:ff:ff:ff
inet 10.10.10.1/26 brd 10.10.1.191 scope global noprefixroute eth0

Pretty much expected MAC is on keepalived node server1.

 

7. Testing keepalived on server1 and server2 maachines VIP floating IP really works
 

To test the overall configuration just created, you should stop keeaplived on the Master node and in meantime keep an eye on Slave node (server2), whether it can figure out the Master node is gone and switch its
state BACKUP to save MASTER. By changing the secondary (Slave) keepalived to master the floating IP: 10.10.10.1 will be brought up by the scripts on server2.

Lets assume that something went wrong with server1 VM host, for example the machine crashed due to service overload, DDoS or simply a kernel bug or whatever reason.
To simulate that we simply have to stop keepalived, then the broadcasted information on VRRP TCP/IP proto port 112 will be no longer available and keepalived on node server2, once
unable to communicate to server1 should chnage itself to state MASTER.

[root@server1:~]# systemctl stop keepalived
[root@server1:~]# systemctl status keepalived
● keepalived.service – LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; vendor preset: disabled)
   Active: inactive (dead) since Tue 2022-03-15 12:11:33 CET; 3s ago
  Process: 1192001 ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 1192002 (code=exited, status=0/SUCCESS)

Mar 14 18:59:07 server1lb-fqdn Keepalived_vrrp[1192003]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:32 server1lb-fqdn systemd[1]: Stopping LVS and VRRP High Availability Monitor…
Mar 15 12:11:32 server1lb-fqdn Keepalived[1192002]: Stopping
Mar 15 12:11:32 server1lb-fqdn Keepalived_vrrp[1192003]: (LB_VIP_QA) sent 0 priority
Mar 15 12:11:32 server1lb-fqdn Keepalived_vrrp[1192003]: (LB_VIP_QA) removing VIPs.
Mar 15 12:11:33 server1lb-fqdn Keepalived_vrrp[1192003]: Stopped – used 2.145252 user time, 15.513454 system time
Mar 15 12:11:33 server1lb-fqdn Keepalived[1192002]: CPU usage (self/children) user: 0.000000/44.555362 system: 0.001151/170.118126
Mar 15 12:11:33 server1lb-fqdn Keepalived[1192002]: Stopped Keepalived v2.1.5 (07/13,2020)
Mar 15 12:11:33 server1lb-fqdn systemd[1]: keepalived.service: Succeeded.
Mar 15 12:11:33 server1lb-fqdn systemd[1]: Stopped LVS and VRRP High Availability Monitor.

 

On keepalived off, you will get also a notification Email on the Receipt Email configured from keepalived.conf from the working keepalived node with a simple message like:

=> VRRP Instance is no longer owning VRRP VIPs <=

Once keepalived is back up you will get another notification like:

=> VRRP Instance is now owning VRRP VIPs <=

[root@server2:~]# systemctl status keepalived
● keepalived.service – LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2022-03-14 18:13:52 CET; 17h ago
  Process: 297366 ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 297367 (keepalived)
    Tasks: 2 (limit: 100914)
   Memory: 2.1M
   CGroup: /system.slice/keepalived.service
           ├─297367 /usr/sbin/keepalived -D -S 7
           └─297368 /usr/sbin/keepalived -D -S 7

Mar 15 12:11:33 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:33 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:33 server2lb-fqdn Keepalived_vrrp[297368]: Remote SMTP server [127.0.0.1]:25 connected.
Mar 15 12:11:33 server2lb-fqdn Keepalived_vrrp[297368]: SMTP alert successfully sent.
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: (LB_VIP_QA) Sending/queueing gratuitous ARPs on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1

[root@server2:~]#  ip addr show|grep -i 10.10.10.1
    inet 10.10.10.1/32 scope global eth0
    

As you see the VIP is now set on server2, just like expected – that's OK, everything works as expected. If the IP did not move double check the keepalived.conf on both nodes for errors or misconfigurations.

To recover the initial order of things so server1 is MASTER and server2 SLAVE host, we just have to switch on the keepalived on server1 machine.

[root@server1:~]# systemctl start keepalived

The automatic change of server1 to MASTER node and respective move of the VIP IP is done because of the higher priority (of importance we previously configured on server1 in keepalived.conf).
 

What we learned?
 

So what we learned in  this article?
We have seen how to easily install and configure a High Availability Load balancer with Keepalived with single floating VIP IP address with 1 MASTER and 1 SLAVE host and a Haproxy example config with few frontends / App backends. We have seen how the config can be tested for potential errors and how we can monitor whether the VRRP2 network traffic flows between nodes and how to potentially debug it further if necessery.
Further on rawly explained some of the keepalived configurations but as keepalived can do pretty much more,for anyone seriously willing to deal with keepalived on a daily basis or just fine tune some already existing ones, you better read closely its manual page "man keepalived.conf" as well as the official Redhat Linux documentation page on setting up a Linux cluster with Keepalived (Be prepare for a small nightmare as the documentation of it seems to be a bit chaotic, and even I would say partly missing or opening questions on what does the developers did meant – not strange considering the havoc that is pretty much as everywhere these days.)

Finally once keepalived hosts are prepared, it was shown how to test the keepalived application cluster and Floating IP does move between nodes in case if one of the 2 keepalived nodes is inaccessible.

The same logic can be repeated multiple times and if necessery you can set multiple VIPs to expand the HA reachable IPs solution.

high-availability-with-two-vips-example-diagram

The presented idea is with haproxy forward Proxy server to proxy requests towards Application backend (servince machines), however if you need to set another set of server on the flow to  process HTML / XHTML / PHP / Perl / Python  programming code, with some common Webserver setup ( Nginx / Apache / Tomcat / JBOSS) and enable SSL Secure certificate with lets say Letsencrypt, this can be relatively easily done. If you want to implement letsencrypt and a webserver check this redundant SSL Load Balancing with haproxy & keepalived article.

That's all folks, hope you enjoyed.
If you need to configure keepalived Cluster or a consultancy write your query here 🙂

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Posted in Cloud services, Educational, Haproxy, Keepalived, System Administration | No Comments »

Configure own Media streaming minidlna Linux server to access data from your Smart TV

Friday, February 18th, 2022

dlna-media-minidlna-server-linux-logo

If you happen to buy or already own or just have to install a Smart TV to be connected with a LAN Network to a Linux based custom built NAS (Network Attached Storage) server. You might benefit of the smart TV to Share and Watching the Disk Storage Pictures, Music, Video files from the NAS  to the Smart TV using the Media Server protocol.

You have certainly already faced the Media Server at your life on many locations in stores and Mall Buildings, because virtually any reoccuring advertisements, movies projected on the TVs, Kids entertainment or Floor and Buildings Room location schedules or timeline promition schedules are streamed using the Media Server protocol, for many years now. Thus having a brief idea about Media Server proto existence is foundamental stuff to be aware of for sysadmins and programmers.

Shortly about DLNA UPnP Media Streaming Protocol

Assuming that your Smart TV has been already connected to your Wireless Router 2.4Ghz or 5Ghz Wifi, one would think that the easiest way to share the files with the SmartTV is via something like a simple SAMBA Linux server via smb:// cifs:// protocols or via the good old NFS Server, however most of Samsung Smart TV and many other in year 2022 does not have embedded support for Samba SMB / CIFS Protocol but instead have support for the DLNA (Digital Living Network Alliance) streaming support. DLNA is part of the UPnP (Universal Plug and Play) Protocols, UPnP is also known to those using and familiar with Windows Operating Systems realm simply as UPnP AV Media server or Windows Media server.
Windows Media server for those who never heard it or used it  allows you to build a Playlists with Media files Video and Audio data files, that can be then later played remotely via a Local LAN or even long distance over TCP / IP remote side connected Internet network.
 

1. Set up and Stream data via Media server on  Windows PC / notebook with integrated Windows Media server 

Windows Media server configuration on Windows 7, 10 and 11 is a relatively easy to configure via:

Network and Sharing Center -> Media Streaming Options -> Turn on Media Streaming 


Then you have to define the name of the Media Library, configure whether Media server should show
on the Local Netework for other conected devices and Allow or Block access from the other network present devices.


 2. Using a more advanced Media Server to get rid about the limitation of DLNA set of supported file codecs.
 

The Windows default embedded DLNA server is the easiest and fastest one to set up, but it’s not necessarily the best option.
Due to the way DLNA works, you can only stream certain types of media codecs supported by the server. If you have other types of media not defaultly supported and defined by DLNA win server, it just won’t work.

Thus thanksfully it was developed other DLNA servers improve this by offering real-time transcoding.
If you try to play an unsupported file, they’ll transcode it on-the-fly, streaming the video in a supported format to your DLNA device.
Just to name few of the DLNA Media Streaming servers that have supported for larger MPG Video, MP3 / MP4 and other Audio formats encodings,
you can try Plex or the Universal Media Server both of which are free to use under freeware license and have versions for Linux and Mac OS.


Universal_media_server-windows-screenshot-stream-media-data-on-network

 

3. Setting up a free as in freedom DLNA server MiniDLNA (ReadyMedia) on GNU / Linux


ReadyMedia (formerly known as MiniDLNA) is a simple media server software, with the aim of being fully compliant with DLNA/UPnP-AV clients. It was originally developed by a NETGEAR employee for the ReadyNAS product line.

MiniDNLA daemon serves media files (music, pictures, and video) to clients on a network. Linux Media servers clients you can use to test or scan your network for existent Media servers are multiple perhaps the most famous ones are applications such as totem (for QT users) and Kodi (for KDE).
The devices that can be used with minidlna are devices such as portable media players (iPod), Smartphones, Televisions, Tablets, and gaming systems (such as PS3 and Xbox 360) etc.
 

ReadyMedia is a simple, lightweight, the downside of it is It does not have a web interface for administration and must be configured by editing a text file. But for a simple Video streaming in most cases does a great job.


3.1 Install the minidlna software package 

Minidlna is available out of the box on most linux distributions (Fedora / CentOS / Debian / Ubuntu etc.) as of year 2022.

  • Install on Debian Linux (Deb based distro)

media-server:~# apt install minidlna –yes

  • Install on Fedora / CentOS (other RPM based distro)

media-server:~# yum install -y minidlna


3.2 Configure minidlna

– /etc/minidlna.conf – main config file
Open with text editor and set user= ,  media_dir= ,  port=, friendly_name= ,  network_interface= variables as minimum.
To be add minidlnad support symlinks to external file locations, set also wide_links=yes

media-server:~# vim /etc/minidlna.conf

#user=minidlna
user=root
media_dir=/var/www/owncloud/data
network_interface=eth0,eth1

# Port number for HTTP traffic (descriptions, SOAP, media transfer).
# This option is mandatory (or it must be specified on the command-line using
# "-p").
port=8200
# Name that the DLNA server presents to clients.
# Defaults to "hostname: username".
#friendly_name=
friendly_name=DLNAServer Linux
# set this to yes to allow symlinks that point outside user-defined media_dirs.
wide_links=yes
# Automatic discovery of new files in the media_dir directory.
#inotify=yes

Keep in mind that it is supported to provide separete media_dir and provide different USB / External Hard Drive or SD Card sources separated only by content be it Video, Audio or Pictures short named in config as (A,V,P).

media_dir=P,/media/usb/photos
media_dir=V,/media/external-disk/videos
media_dir=A,/media/sd-card/music

You might want to diasble / ineable the inotify depending on your liking, if you don't plan to place new files automated to the NAS and don't care to get indexed and streamed from the Media server you can disable it with inotify=no otherwise keep that on.

– /etc/default/minidlna – additional startup config to set minidlnad (daemon) options such as setup to run with admin superuser root:root 
(usually it is safe to leave it empty and set the user=root, whether needed straight from /etc/minidlna.conf
That's all now go on and launch the minidlna and enable it to automatically boot on Linux boot.

media-server:~# systemctl start minidlna
media-server:~# systemctl enable minidlna
media-server:~# systemctl status minidlna

 

3.3 Rebuilt minidlna database with data indexed files

If you need to re- generate minidlna's database.
To do so stop the minidlna server with the
 

media-server:~# systemctop stop minidlna


 command, then issue the following command (both commands should be run as root):

media-server:~# minidlna -R

Since this command might kept in the background and keep the minidlna server running with incorrect flags, after a minute or two kill minidlna process and relaunch the server via sysctl.

media-server:~#  killall -9 minidlna
media-server:~#  systemctl start minidlna

 

3.4 Permission Issues / Scanning issues

If you plan to place files in /home directory. You better have a seperate partition or folder *outside* your "home" directory devoted to your media. Default user with which minidlna runs is minidlna, this could prevent some files with root or other users being red. So either run minidlna daemon as root or as other user with whom all media files should be accessible.
If service runs as root:root, and still getting some scanning issues, check permissions on your files and remove special characters from file names.
 

media-server:~# tail -10 /var/log/minidlna/minidlna.log 
[2022/02/17 22:51:36] scanner.c:489: warn: Unsuccessful getting details for /var/www/owncloud/data/Videos/Family-Videos/FILE006.MPG
[2022/02/17 22:52:08] scanner.c:819: warn: Scanning /var/www/owncloud/data finished (10637 files)!
[2022/02/17 22:52:08] playlist.c:135: warn: Parsing playlists…
[2022/02/17 22:52:08] playlist.c:269: warn: Finished parsing playlists.
minidlna.c:1126: warn: Starting MiniDLNA version 1.3.0.
minidlna.c:1186: warn: HTTP listening on port 8200
scanner.c:489: warn: Unsuccessful getting details for /var/www/owncloud/data/admin/files/origin/External SD card/media/Viber Images/IMG-4477de7b1eee273d5e6ae25236c5c223-V.jpg
scanner.c:489: warn: Unsuccessful getting details for /var/www/owncloud/data/Videos/Family-Video/FILE006.MPG
playlist.c:135: warn: Parsing playlists…
playlist.c:269: warn: Finished parsing playlists.

 

3.5. Fix minidlna Inotify errors

In /etc/sysctl.conf 

Add:

fs.inotify.max_user_watches=65536

in a blank line at end of file and do 

media-server:~# sysctl -p

Debugging minidlna problems, index errors, warnings etc

minidlna does write by default to /var/log/minidlna/minidlna.log inspect the log closely and you should get most of the time what is wrong with it.
Note that some files might not get indexed because minidlna won't support the strange file codecs such as SWF encoding, if you have some important files to stream that are not indexed by minidlna, then install and try one of the more sophisticated free software Media Servers for Linux:

plex-media-streaming-server-screenshot

Note that most Linux users from my quick research shows, MediaTomb is the preferred advanced features Open Source Linux Media Server of choice for most of the guys.

mediatomb-linux-media-streaming-server-picture.jpg.webp
 

 

4. Test minidlna Linux servers works, getting information of other DLNA Servers on the network

media-server:~# lynx -dump  http://127.0.0.1:8200
MiniDLNA status

  Media library

   Audio files 0
   Video files 455
   Image files 10182

  Connected clients

   ID Type                   IP Address    HW Address        Connections
   0  Samsung Series [CDEFJ] 192.168.1.11  7C:0A:3D:88:A6:FA 0
   1  Generic DLNA 1.5       192.168.0.241 00:16:4E:1D:48:05 0
   2  Generic DLNA 1.5       192.168.1.18  00:16:3F:0D:45:05 0
   3  Unknown                127.0.0.1     FF:FF:FF:FF:FF:FF 0

   -1 connections currently open
 

Note that there is -1 connections (no active connections) currently to the server. 
The 2 Generic DLNA 1.5 IPs are another DLNA servers provided by a OpenXEN hosted Windows 7 Virtual machines, that are also broadcasting their existence in the network. The Samsung Series [CDEFJ] is the DLNA client on the Samsung TV found, used to detect and stream data from the just configured Linux dlna server.

The DLNA Protocol enabled devices on a network as you can see are quite easy to access, querying localhost on the 8200 server dumps, what minidlna knows, the rest of IPs connecting should not be able to receive this info. But anyways since the minidlna does not have a special layers of security to access it, but the only way to restrict is filtering the 8200 port, it is a very good idea to put a good iptables firewall on the machine to allow only the devices that should have access to the data.

Further more if you happen to need to access the Media files on Linux from GUI you might use some client as upmentioned totem, VLC or if you need something more feature rich Java eezUPnP .

eeZUPnP-screenshot-java-client-for-media-server

That's all folks !
Enjoy your media on the TV 🙂

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Posted in Entertainment, Linux, Video Streaming | No Comments »

How to filter dhcp traffic between two networks running separate DHCP servers to prevent IP assignment issues and MAC duplicate addresses

Tuesday, February 8th, 2022

how-to-filter-dhcp-traffic-2-networks-running-2-separate-dhcpd-servers-to-prevent-ip-assignment-conflicts-linux
Tracking the Problem of MAC duplicates on Linux routers
 

If you have two networks that see each other and they're not separated in VLANs but see each other sharing a common netmask lets say 255.255.254.0 or 255.255.252.0, it might happend that there are 2 dhcp servers for example (isc-dhcp-server running on 192.168.1.1 and dhcpd running on 192.168.0.1 can broadcast their services to both LANs 192.168.1.0.1/24 (netmask 255.255.255.0) and Local Net LAN 192.168.1.1/24. The result out of this is that some devices might pick up their IP address via DHCP from the wrong dhcp server.

Normally if you have a fully controlled little or middle class home or office network (10 – 15 electronic devices nodes) connecting to the LAN in a mixed moth some are connected via one of the Networks via connected Wifi to 192.168.1.0/22 others are LANned and using static IP adddresses and traffic is routed among two ISPs and each network can see the other network, there is always a possibility of things to go wrong. This is what happened to me so this is how this post was born.

The best practice from my experience so far is to define each and every computer / phone / laptop host joining the network and hence later easily monitor what is going on the network with something like iptraf-ng / nethogs  / iperf – described in prior  how to check internet spepeed from console and in check server internet connectivity speed with speedtest-cli) iftop / nload or for more complex stuff wireshark or even a simple tcpdump. No matter the tools network monitoring is only part on solving network issues. A very must have thing in a controlled network infrastructure is defining every machine part of it to easily monitor later with the monitoring tools. Defining each and every host on the Hybrid computer networks makes administering the network much easier task and  tracking irregularities on time is much more likely. 

Since I have such a hybrid network here hosting a couple of XEN virtual machines with Linux, Windows 7 and Windows 10, together with Mac OS X laptops as well as MacBook Air notebooks, I have followed this route and tried to define each and every host based on its MAC address to pick it up from the correct DHCP1 server  192.168.1.1 (that is distributing IPs for Internet Provider 1 (ISP 1), that is mostly few computers attached UTP LAN cables via LiteWave LS105G Gigabit Switch as well from DHCP2 – used only to assigns IPs to servers and a a single Wi-Fi Access point configured to route incoming clients via 192.168.0.1 Linux NAT gateway server.

To filter out the unwanted IPs from the DHCPD not to propagate I've so far used a little trick to  Deny DHCP MAC Address for unwanted clients and not send IP offer for them.

To give you more understanding,  I have to clear it up I don't want to have automatic IP assignments from DHCP2 / LAN2 to DHCP1 / LAN1 because (i don't want machines on DHCP1 to end up with IP like 192.168.0.50 or DHCP2 (to have 192.168.1.80), as such a wrong IP delegation could potentially lead to MAC duplicates IP conflicts. MAC Duplicate IP wrong assignments for those older or who have been part of administrating large ISP network infrastructures  makes the network communication unstable for no apparent reason and nodes partially unreachable at times or full time …

However it seems in the 21-st century which is the century of strangeness / computer madness in the 2022, technology advanced so much that it has massively started to break up some good old well known sysadmin standards well documented in the RFCs I know of my youth, such as that every electronic equipment manufactured Vendor should have a Vendor Assigned Hardware MAC Address binded to it that will never change (after all that was the idea of MAC addresses wasn't it !). 
Many mobile devices nowadays however, in the developers attempts to make more sophisticated software and Increase Anonimity on the Net and Security, use a technique called  MAC Address randomization (mostly used by hackers / script kiddies of the early days of computers) for their Wi-Fi Net Adapter OS / driver controlled interfaces for the sake of increased security (the so called Private WiFi Addresses). If a sysadmin 10-15 years ago has seen that he might probably resign his profession and turn to farming or agriculture plant growing, but in the age of digitalization and "cloud computing", this break up of common developed network standards starts to become the 'new normal' standard.

I did not suspected there might be a MAC address oddities, since I spare very little time on administering the the network. This was so till recently when I accidently checked the arp table with:

Hypervisor:~# arp -an
192.168.1.99     5c:89:b5:f2:e8:d8      (Unknown)
192.168.1.99    00:15:3e:d3:8f:76       (Unknown)

..


and consequently did a network MAC Address ARP Scan with arp-scan (if you never used this little nifty hacker tool I warmly recommend it !!!)
If you don't have it installed it is available in debian based linuces from default repos to install

Hypervisor:~# apt-get install –yes arp-scan
…


It is also available on CentOS / Fedora / Redhat and other RPM distros via:

Hypervisor:~# yum install -y arp-scan
…

 

 

Hypervisor:~# arp-scan –interface=eth1 192.168.1.0/24
…

192.168.1.19    00:16:3e:0f:48:05       Xensource, Inc.
192.168.1.22    00:16:3e:04:11:1c       Xensource, Inc.
192.168.1.31    00:15:3e:bb:45:45       Xensource, Inc.
192.168.1.38    00:15:3e:59:96:8e       Xensource, Inc.
192.168.1.34    00:15:3e:d3:8f:77       Xensource, Inc.
192.168.1.60    8c:89:b5:f2:e8:d8       Micro-Star INT'L CO., LTD
192.168.1.99     5c:89:b5:f2:e8:d8      (Unknown)
192.168.1.99    00:15:3e:d3:8f:76       (Unknown)
192.168.x.91     02:a0:xx:xx:d6:64        (Unknown)
192.168.x.91     02:a0:xx:xx:d6:64        (Unknown)  (DUP: 2)
…

N.B. !. I found it helpful to check all available interfaces on my Linux NAT router host.

As you see the scan revealed, a whole bunch of MAC address mess duplicated MAC hanging around, destroying my network topology every now and then 
So far so good, the MAC duplicates and strangely hanging around MAC addresses issue, was solved relatively easily with enabling below set of systctl kernel variables.
 

1. Fixing Linux ARP common well known Problems through disabling arp_announce / arp_ignore / send_redirects kernel variables disablement

 

Linux answers ARP requests on wrong and unassociated interfaces per default. This leads to the following two problems:

ARP requests for the loopback alias address are answered on the HW interfaces (even if NOARP on lo0:1 is set). Since loopback aliases are required for DSR (Direct Server Return) setups this problem is very common (but easy to fix fortunately).

If the machine is connected twice to the same switch (e.g. with eth0 and eth1) eth2 may answer ARP requests for the address on eth1 and vice versa in a race condition manner (confusing almost everything).

This can be prevented by specific arp kernel settings. Take a look here for additional information about the nature of the problem (and other solutions): ARP flux.

To fix that generally (and reboot safe) we  include the following lines into

 

Hypervisor:~# cp -rpf /etc/sysctl.conf /etc/sysctl.conf_bak_07-feb-2022
Hypervisor:~# cat >> /etc/sysctl.conf

# LVS tuning
net.ipv4.conf.lo.arp_ignore=1
net.ipv4.conf.lo.arp_announce=2
net.ipv4.conf.all.arp_ignore=1
net.ipv4.conf.all.arp_announce=2

net.ipv4.conf.all.send_redirects=0
net.ipv4.conf.eth0.send_redirects=0
net.ipv4.conf.eth1.send_redirects=0
net.ipv4.conf.default.send_redirects=0

Press CTRL + D simultaneusly to Write out up-pasted vars.


To read more on Load Balancer using direct routing and on LVS and the arp problem here


2. Digging further the IP conflict / dulicate MAC Problems

Even after this arp tunings (because I do have my Hypervisor 2 LAN interfaces connected to 1 switch) did not resolved the issues and still my Wireless Connected devices via network 192.168.1.1/24 (ISP2) were randomly assigned the wrong range IPs 192.168.0.XXX/24 as well as the wrong gateway 192.168.0.1 (ISP1).
After thinking thoroughfully for hours and checking the network status with various tools and thanks to the fact that my wife has a MacBook Air that was always complaining that the IP it tried to assign from the DHCP was already taken, i"ve realized, something is wrong with DHCP assignment.
Since she owns a IPhone 10 with iOS and this two devices are from the same vendor e.g. Apple Inc. And Apple's products have been having strange DHCP assignment issues from my experience for quite some time, I've thought initially problems are caused by software on Apple's devices.
I turned to be partially right after expecting the logs of DHCP server on the Linux host (ISP1) finding that the phone of my wife takes IP in 192.168.0.XXX, insetad of IP from 192.168.1.1 (which has is a combined Nokia Router with 2.4Ghz and 5Ghz Wi-Fi and LAN router provided by ISP2 in that case Vivacom). That was really puzzling since for me it was completely logical thta the iDevices must check for DHCP address directly on the Network of the router to whom, they're connecting. Guess my suprise when I realized that instead of that the iDevices does listen to the network on a wide network range scan for any DHCPs reachable baesd on the advertised (i assume via broadcast) address traffic and try to connect and take the IP to the IP of the DHCP which responds faster !!!! Of course the Vivacom Chineese produced Nokia router responded DHCP requests and advertised much slower, than my Linux NAT gateway on ISP1 and because of that the Iphone and iOS and even freshest versions of Android devices do take the IP from the DHCP that responds faster, even if that router is not on a C class network (that's invasive isn't it??). What was even more puzzling was the automatic MAC Randomization of Wifi devices trying to connect to my ISP1 configured DHCPD and this of course trespassed any static MAC addresses filtering, I already had established there.

Anyways there was also a good think out of tthat intermixed exercise 🙂 While playing around with the Gigabit network router of vivacom I found a cozy feature SCHEDULEDING TURNING OFF and ON the WIFI ACCESS POINT  – a very useful feature to adopt, to stop wasting extra energy and lower a bit of radiation is to set a swtich off WIFI AP from 12:30 – 06:30 which are the common sleeping hours or something like that.
 

3. What is MAC Randomization and where and how it is configured across different main operating systems as of year 2022?

Depending on the operating system of your device, MAC randomization will be available either by default on most modern mobile OSes or with possibility to have it switched on:

  • Android Q: Enabled by default 
  • Android P: Available as a developer option, disabled by default
  • iOS 14: Available as a user option, disabled by default
  • Windows 10: Available as an option in two ways – random for all networks or random for a specific network

Lately I don't have much time to play around with mobile devices, and I do not my own a luxury mobile phone so, the fact this ne Androids have this MAC randomization was unknown to me just until I ended a small mess, based on my poor configured networks due to my tight time constrains nowadays.

Finding out about the new security feature of MAC Randomization, on all Android based phones (my mother's Nokia smartphone and my dad's phone, disabled the feature ASAP:


4. Disable MAC Wi-Fi Ethernet device Randomization on Android

MAC Randomization creates a random MAC address when joining a Wi-Fi network for the first time or after “forgetting” and rejoining a Wi-Fi network. It Generates a new random MAC address after 24 hours of last connection.

Disabling MAC Randomization on your devices. It is done on a per SSID basis so you can turn off the randomization, but allow it to function for hotspots outside of your home.

  1. Open the Settings app
  2. Select Network and Internet
  3. Select WiFi
  4. Connect to your home wireless network
  5. Tap the gear icon next to the current WiFi connection
  6. Select Advanced
  7. Select Privacy
  8. Select "Use device MAC"
     

5. Disabling MAC Randomization on MAC iOS, iPhone, iPad, iPod

To Disable MAC Randomization on iOS Devices:

Open the Settings on your iPhone, iPad, or iPod, then tap Wi-Fi or WLAN

 

  1. Tap the information button next to your network
  2. Turn off Private Address
  3. Re-join the network


Of course next I've collected their phone Wi-Fi adapters and made sure the included dhcp MAC deny rules in /etc/dhcp/dhcpd.conf are at place.

The effect of the MAC Randomization for my Network was terrible constant and strange issues with my routings and networks, which I always thought are caused by the openxen hypervisor Virtualization VM bugs etc.

That continued for some months now, and the weird thing was the issues always started when I tried to update my Operating system to the latest packetset, do a reboot to load up the new piece of software / libraries etc. and plus it happened very occasionally and their was no obvious reason for it.

 

6. How to completely filter dhcp traffic between two network router hosts
IP 192.168.0.1 / 192.168.1.1 to stop 2 or more configured DHCP servers
on separate networks see each other

To prevent IP mess at DHCP2 server side (which btw is ISC DHCP server, taking care for IP assignment only for the Servers on the network running on Debian 11 Linux), further on I had to filter out any DHCP UDP traffic with iptables completely.
To prevent incorrect route assignments assuming that you have 2 networks and 2 routers that are configurred to do Network Address Translation (NAT)-ing Router 1: 192.168.0.1, Router 2: 192.168.1.1.

You have to filter out UDP Protocol data on Port 67 and 68 from the respective source and destination addresses.

In firewall rules configuration files on your Linux you need to have some rules as:

# filter outgoing dhcp traffic from 192.168.1.1 to 192.168.0.1
-A INPUT -p udp -m udp –dport 67:68 -s 192.168.1.1 -d 192.168.0.1 -j DROP
-A OUTPUT -p udp -m udp –dport 67:68 -s 192.168.1.1 -d 192.168.0.1 -j DROP
-A FORWARD -p udp -m udp –dport 67:68 -s 192.168.1.1 -d 192.168.0.1 -j DROP

-A INPUT -p udp -m udp –dport 67:68 -s 192.168.0.1 -d 192.168.1.1 -j DROP
-A OUTPUT -p udp -m udp –dport 67:68 -s 192.168.0.1 -d 192.168.1.1 -j DROP
-A FORWARD -p udp -m udp –dport 67:68 -s 192.168.0.1 -d 192.168.1.1 -j DROP

-A INPUT -p udp -m udp –sport 67:68 -s 192.168.1.1 -d 192.168.0.1 -j DROP
-A OUTPUT -p udp -m udp –sport 67:68 -s 192.168.1.1 -d 192.168.0.1 -j DROP
-A FORWARD -p udp -m udp –sport 67:68 -s 192.168.1.1 -d 192.168.0.1 -j DROP


You can download also filter_dhcp_traffic.sh with above rules from here


Applying this rules, any traffic of DHCP between 2 routers is prohibited and devices from Net: 192.168.1.1-255 will no longer wrongly get assinged IP addresses from Network range: 192.168.0.1-255 as it happened to me.


7. Filter out DHCP traffic based on MAC completely on Linux with arptables

If even after disabling MAC randomization on all devices on the network, and you know physically all the connecting devices on the Network, if you still see some weird MAC addresses, originating from a wrongly configured ISP traffic router host or whatever, then it is time to just filter them out with arptables.

## drop traffic prevent mac duplicates due to vivacom and bergon placed in same network – 255.255.255.252
dchp1-server:~# arptables -A INPUT –source-mac 70:e2:83:12:44:11 -j DROP


To list arptables configured on Linux host

dchp1-server:~# arptables –list -n


If you want to be paranoid sysadmin you can implement a MAC address protection with arptables by only allowing a single set of MAC Addr / IPs and dropping the rest.

dchp1-server:~# arptables -A INPUT –source-mac 70:e2:84:13:45:11 -j ACCEPT
dchp1-server:~# arptables -A INPUT  –source-mac 70:e2:84:13:45:12 -j ACCEPT


dchp1-server:~# arptables -L –line-numbers
Chain INPUT (policy ACCEPT)
1 -j DROP –src-mac 70:e2:84:13:45:11
2 -j DROP –src-mac 70:e2:84:13:45:12
3 

Once MACs you like are accepted you can set the INPUT chain policy to DROP as so:

dchp1-server:~# arptables -P INPUT DROP


If you later need to temporary, clean up the rules inside arptables on any filtered hosts flush all rules inside INPUT chain, like that
 

dchp1-server:~#  arptables -t INPUT -F

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