How to set up Notify by email expiring local UNIX user accounts on Linux / BSD with a bash script

August 24th, 2023


If you have already configured Linux Local User Accounts Password Security policies Hardening – Set Password expiry, password quality, limit repatead access attempts, add directionary check, increase logged history command size and you want your configured local user accounts on a Linux / UNIX / BSD system to not expire before the user is reminded that it will be of his benefit to change his password on time, not to completely loose account to his account, then you might use a small script that is just checking the upcoming expiry for a predefined users and emails in an array with lslogins command like you will learn in this article.

The script below is written by a colleague Lachezar Pramatarov (Credit for the script goes to him) in order to solve this annoying expire problem, that we had all the time as me and colleagues often ended up with expired accounts and had to bother to ask for the password reset and even sometimes clearance of account locks. Hopefully this little script will help some other unix legacy admin systems to get rid of the account expire problem.

For the script to work you will need to have a properly configured SMTP (Mail server) with or without a relay to be able to send to the script predefined email addresses that will get notified. 

Here is example of a user whose account is about to expire in a couple of days and who will benefit of getting the Alert that he should hurry up to change his password until it is too late 🙂

[root@linux ~]# date
Thu Aug 24 17:28:18 CEST 2023

[root@server~]# chage -l lachezar
Last password change                                    : May 30, 2023
Password expires                                        : Aug 28, 2023
Password inactive                                       : never
Account expires                                         : never
Minimum number of days between password change          : 0
Maximum number of days between password change          : 90
Number of days of warning before password expires       : 14

Here is the that will report the user

# vim  /usr/local/bin/


# This script will send warning emails for password expiration 
# on the participants in the following list:
# 20, 15, 10 and 0-7 days before expiration
# ! Script sends expiry Alert only if day is Wednesday – if (( $(date +%u)==3 )); !

# email to send if expiring
# the users that are admins added to belong to this group
notify_email_header_customer_name='Customer Name';

declare -A mails=(
# list below accounts which will receive account expiry emails

# syntax to define uid / email
# [“account_name_from_etc_passwd”]="real_email_addr@fqdn";

#    [“abc”]=""
#    [“cba”]=""
#    [“acct7”]=""
#    [“acct8”]=""
#    [“acct9”]=""

declare -A days

while IFS="=" read -r person day ; do
done < <(lslogins –noheadings -o USER,GROUP,PWD-CHANGE,PWD-WARN,PWD-MIN,PWD-MAX,PWD-EXPIR,LAST-LOGIN,FAILED-LOGIN  –time-format=iso | awk '{print "echo "$1" "$2" "$3" $(((($(date +%s -d \""$3"+90 days\")-$(date +%s)))/86400)) "$5}' | /bin/bash | grep -E " $admin_group " | awk '{print $1 "=" $4}')

#echo ${days[laprext]}
for person in "${!mails[@]}"; do
     echo "$person ${days[$person]}";

#     echo $tmp
# each person will receive mails only if 20th days / 15th days / 10th days remaining till expiry or if less than 7 days receive alert mail every day

     if  (( (${tmp}==20) || (${tmp}==15) || (${tmp}==10) || ((${tmp}>=0) && (${tmp}<=7)) )); 
         echo "Hello, your password for $(hostname -s) will expire after ${days[$person]} days.” | mail -s “$notify_email_header_customer_name $(hostname -s) server password expiration”  -r passwd_expire ${mails[$person]};
     elif ((${tmp}<0));
#          echo "The password for $person on $(hostname -s) has EXPIRED before{days[$person]} days. Please take an action ASAP.” | mail -s “EXPIRED password of  $person on $(hostname -s)”  -r EXPIRED ${mails[$person]};

# ==3 meaning day is Wednesday the day on which OnCall Person changes

        if (( $(date +%u)==3 ));
             echo "The password for $person on $(hostname -s) has EXPIRED. Please take an action." | mail -s "EXPIRED password of  $person on $(hostname -s)"  -r EXPIRED $alert_email;


To make the script notify about expiring user accounts, place the script under some directory lets say /usr/local/bin/ and make it executable and configure a cron job that will schedule it to run every now and then.

# cat /etc/cron.d/passwd_expire_cron

# /etc/cron.d/pwd_expire
# Check password expiration for users
# 2023-01-16 LPR
02 06 * * * root /usr/local/bin/ >/dev/null

Script will execute every day morning 06:02 by the cron job and if the day is wednesday (3rd day of week) it will send warning emails for password expiration if 20, 15, 10 days are left before account expires if only 7 days are left until the password of user acct expires, the script will start sending the Alarm every single day for 7th, 6th … 0 day until pwd expires.

If you don't have an expiring accounts and you want to force a specific account to have a expire date you can do it with:

# chage -E 2023-08-30 someuser

Or set it for new created system users with:

# useradd -e 2023-08-30 username

That's it the script will notify you on User PWD expiry.

If you need to for example set a single account to expire 90 days from now (3 months) that is a kind of standard password expiry policy admins use, do it with:

# date -d "90 days" +"%Y-%m-%d"

Ideas for script improvement

The downside of the script if you have too many local user accounts is you have to hardcode into it the username and user email_address attached to and that would be tedios task if you have 100+ accounts. 

However it is pretty easy if you already have a multitude of accounts in /etc/passwd that are from UID range to loop over them in a small shell loop and build new array from it. Of course for a solution like this to work you will have to have defined as user data as GECOS with command like chfn.

[georgi@server ~]$ chfn
Changing finger information for test.
Name [test]: 
Office []:
Office Phone []: 
Home Phone []: 


[root@server test]# finger georgi
Login: georgi                       Name: georgi
Directory: /home/georgi                   Shell: /bin/bash
On since чт авг 24 17:41 (EEST) on :0 from :0 (messages off)
On since чт авг 24 17:43 (EEST) on pts/0 from :0
   2 seconds idle
On since чт авг 24 17:44 (EEST) on pts/1 from :0
   49 minutes 30 seconds idle
On since чт авг 24 18:04 (EEST) on pts/2 from :0
   32 minutes 42 seconds idle
New mail received пт окт 30 17:24 2020 (EET)
     Unread since пт окт 30 17:13 2020 (EET)
No Plan.

Then it should be relatively easy to add the GECOS for multilpe accounts if you have them predefined in a text file for each existing local user account.

Hope this script will help some sysadmin out there, many thanks to Lachezar for allowing me to share the script here.
Enjoy ! 🙂

Fix ruby: /usr/lib/ version `XCRYPT_2.0′ not found in apt upgrade on Debian Linux 10

August 5th, 2023

I've an old legacy Thinkpad Laptop that is for simplicty running Window Maker Wmaker which was laying on my home desk for almost an year and I remembered since i'm for few days in my parents home in Dobrich that it will be a good idea to update its software to the latest Debian packages to patch security issues with it. Thus if you're like me and  you tried to update your Debian 10 Linux to the latest Stable release debian packages  and you end up into a critical error that is preventing apt to to resolve conflicts (fix it with) cmds like:

# apt-get update –fix-missing

# apt –fix-broken install

As usual I looked into Google to see about solution and found few articles, claiming to have scripts that fix it but at the end nothing worked.
And the shitty error occured during the standard:

# apt-get update && apt-get upgrade

ruby: /usr/lib/ version `XCRYPT_2.0' not found

Hence the cause and work around seemed to be very unexpected.
For some reason debian makes a link

root@noah:/lib# ls -al /lib/
lrwxrwxrwx 1 root root 19 Aug  3 16:53 /lib/ ->

root@noah:/lib# ls -al /lib/
lrwxrwxrwx 1 root root 16 Jun 15  2017 /lib/ ->

Thus to resolve it and force the .deb upgrade package to continue it is up to simply deleting the strange simlink and re-run the

# apt-get update && apt-get upgrade

Setting up libc6:i386 (2.31-13+deb11u6) …
/usr/bin/perl: /lib/ version `XCRYPT_2.0' not found (required by /usr/bin/perl)
dpkg: error processing package libc6:i386 (–configure):
 installed libc6:i386 package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:

Few more times. If you get some critical apt failures still, each time make sure to rerun the command after doing a simple removal of the strange simbolic link with cmd:

# rm -f /lib/

That's all folks after a short while your Debian will be updated to latest Enoy folks ! 🙂

Saint Emilianos (Emilian) of Dorostorum (Silistra) ancient saint venerated in Bulgarian Orthodox Church

August 5th, 2023


Saint Emilian / Emilianos Dorostolski is a martyr revered with a feast day by the Bulgarian Orthodox Church.

According to his biography, he was born in Durostorum (now Silistra Bulgaria), where he spent his life as a servant (or slave) to the mayor.
He lived in the time of Emperor Julian (the apostate).

Emperor Julian sent a new governor to Dorostol charged with the task of eradicating Christianity from the city.

Frightened by his fame as a very cruel ruler, the local inhabitants hide from him that there are Christians among them and declare that they all worship the pagan gods.
Satisfied, he gives a feast to the citizens, but for the zealous Christian Aemilianus (Emilianos), the boasting of the pagan governor is unbearable, and during the feast he smashes the statues of the pagan gods in the sanctuary with a hammer.

An innocent person is accused of the crime, but knowing this, Emilian appears before the governor and confesses his guilt.

The city was fined for harboring Christians, and Aemilianus himself, after torture, was burned at the stake by the Danube[1] (river) on July 18, 362; this date is today the day of his veneration by the church[2].

It is assumed that the life of Saint Emilian was written immediately after the saint's death – the end of the 4th and the beginning of the 5th century. Its earliest variants are generally two.

The first is based on the so-called Codex Vaticanus 866 (published by Boschius in 1868), and the second is based on the so-called Codex Parisiensis of the 9th century (published by François Halkin). Although the Codex Parisiensis largely repeats the Codex Vaticanus, there is a difference between the two lives in both the date of Aemilian's martyrdom and the location of his obituary. According to the first, Emilian was burned at the stake on September 3 in Gedina (localized near the present-day village of Golesh), and according to the second, it happened on July 18 in Gezedina, right next to Durostorum (fortress).

Information about Saint Emilian can also be found in blessed Jerome, and saint Ambrose (Ambrosius) of Milan, Theophanes the Confessor and Nicephorus Callistus.
In the Church-Slavic hagiography, the life enters mainly from its later copies in the Paschal Chronicle (Chronicon Paschalae), the Synaxarium (Church book with the service text dedicated to the sant) of the Constantinople Patriarchate (Synaxarium Constantinopolitanum) and the Monthly Message of Emperor Basil II (Menologium Basilii (Basilius) II).

A major difference between the early lives and their later editions is Aemilian's social status.

According to the late Church Slavonic redactions, he was a slave / servant of the mayor of Durostorum (today city of Silistra Bulgaria), while according to the earlier ones he himself was of noble birth – his father Sevastian was the governor of the city – and was a soldier (presumably from the XI Claudius Legion)[3].



 1. Georgi Atanasov, 345 early Christian saints-martyrs from the Bulgarian lands I – IV centuries / Publisher: Unicart ISBN: 9789542953012 / page 11
  2. Lives of the Saints. Synodal publishing house. Sofia, 1991. pp. 337-338.
  3. St. Emilian Dorostolski: My name is Christian

Other Research sources

  • Constantinesco, R. Les martyrs de Durostorum. – Revue des Etudes Sud-Est Europeennes, 5, 1967, No. 1 – 2, 14 – 19.
  • G. Atanasov. St. Emilian Dorostolsky († 362) – the last early Christian martyr in Mysia. – In: Civitas divino-humana in honor of Professor Georgi Bakalov. S. 2004, 203 – 218.
  • Ivanova, R., G. Atanasov, P. Donevski. History of Silistra. T. 1. The ancient Durostorum. Silistra-S., 2006.
  • Atanasov, G. The Christian Durostorum-Druster. Varna, 2007.

Generate and Add UUID for every existing Redhat / CentOS / RHEL network interface to configuration if missing howto

August 5th, 2023


If you manage old Linux machines it might be after the update either due to update mess or because of old system administrators which manually included the UUID to the config forgot to include it in the present network configuration in /etc/sysconfig/networking-scripts/ifcfg-* Universally Unique IDentifier (UUID)128-bit label I used a small one liner after listing all the existing configured LAN interfaces reported from iproute2 network stack with ip command. As this might be useful to someone out there here is the simple command that returns a number of commands to later just copy paste to console once verified there are no duplicates of the UUID already in the present server configuration with grep.

In overall to correct the configs and reload the network with the proper UUIDs here is what I had to do:

# grep -rli UUID /etc/sysconfig/network-scripts/ifcfg-*

No output from the recursive grep means UUIDs are not present on any existing interface, so we can step further check all the existing machines network ifaces and generate the missing UUIDs with uuidgen command

# ip a s |grep -Ei ': <'|sed -e 's#:##g' |grep -v '\.' |awk '{ print $2 }'


I've stumbled on that case on some legacy Linux inherited from other people sysadmins and in order to place the correct 

# for i in $(ip a s |grep -Ei ': <'|sed -e 's#:##g' |grep -v '\.' |awk '{ print $2 }'); do echo "echo UUID=$(uuidgen $i)"" >> ifcfg-$i"; done|grep -v '\-lo' 
echo UUID=26819d24-9452-4431-a9ca-176d87492b75 >> ifcfg-venet0
echo UUID=3c7e8848-0232-436f-a52a-46db9a03eb33 >> ifcfg-eth0
echo UUID=1fc0454d-bf23-417d-b960-571fc04754d2 >> ifcfg-eth1
echo UUID=5793c1e5-4481-4f09-967e-2cceda85c35f >> ifcfg-eth2
echo UUID=65fdcaf6-d271-4845-a8f1-0ec478c375d1 >> ifcfg-eth3

As you can see I exclude the loopback interface -lo from the ouput as it is not necessery to have UUID for it.
That's all folks problem solved. Enjoy

How to monitor Postfix Mail server work correct with simple one liner Zabbix user parameter script / Simple way to capture and report SMTP machine issues Zabbix template

June 22nd, 2023


In this article, I'm going to show you how to setup a very simple monitoring if a local running SMTP (Postfix / Qmail / Exim) is responding correctly on basic commands. The check would helpfully keep you in track to know whether your configured Linux server local MTA (Mail Transport Agent) is responding on requests on TCP / IP protocol Port 25, as well as a check for process existence of master (that is the main postfix) proccess, as well as the usual postfix spawned sub-processes qmgr (the postfix queue manager), tsl mgr (TLS session cache and PRNG manager), pickup (Postfix local mail pickup) – or email receiving process.


Normally a properly configured postfix installation on a Linux whatever you like distribution would look something like below:

#  ps -ef|grep -Ei 'master|postfix'|grep -v grep
root        1959       1  0 Jun21 ?        00:00:00 /usr/libexec/postfix/master -w
postfix     1961    1959  0 Jun21 ?        00:00:00 qmgr -l -t unix -u
postfix     4542    1959  0 Jun21 ?        00:00:00 tlsmgr -l -t unix -u
postfix  2910288    1959  0 11:28 ?        00:00:00 pickup -l -t unix -u

At times, during mail server restarts the amount of processes that are sub spawned by postfix, may very and if you a do a postfix restart

# systemctl restart postfix

The amout of spawned processes running as postfix username might decrease, and only qmgr might be available for second thus in the consequential shown Template the zabbix processes check to make sure the Postfix is properly operational on the Linux machine is made to check for the absolute minumum of 

1. master (postfix process) that runs with uid root
2. and one (postfix) username binded proccess 

If the amount of processes on the host is less than this minimum number and the netcat is unable to simulate a "half-mail" sent, the configured Postfix alarm Action (media and Email) will take place, and you will get immediately notified, that the monitored Mail server has issue!

The idea is to use a small one liner connection with netcat and half simulate a normal SMTP transaction just like you would normally do:


root@pcfrxen:/root # telnet localhost 25
Connected to localhost.
Escape character is '^]'.
220 This is Mail2 Pc-Freak.NET ESMTP
HELO localhost
250 This is Mail2 Pc-Freak.NET
250 ok


and then disconnect the connection.

1. Create new zabbix userparameter_smtp_check.conf file

The simple userparameter one liner script to do the task looks like this:

# vi /etc/zabbix/zabbix_agent.d/userparameter_smtp_check.conf

UserParameter=smtp.check,(if [[ $(echo -e “HELO localhost\n MAIL FROM: root@$HOSTNAME\n RCPT TO:\n  QUIT\n” | /usr/bin/nc localhost 25 -w 5 2>&1 | grep -Ei ‘220\s.*\sESMTP\sPostfix|250\s\.*|250\s\.*\sOk|250\s\.*\sOk|221\.*\s\w’|wc -l) == ‘5’ ]]; then echo "SMTP OK 1"; else echo "SMTP NOK 0"; fi)

Set the proper permissions so either file is owned by zabbix:zabbix or it is been able to be read from all system users.

# chmod a+r /etc/zabbix/zabbix_agent.d/userparameter_smtp_check.conf

2. Create a new Template for the Mail server monitoring


Just like any other template name it with what fits you as you see, I've call it PROD SMTP Monitoring, as the template is prepared to specifically monitor In Production Linux machines, and a separate template is used to monitor the Quality Assurance (QAs) as well as PreProd (Pre Productions).

3. Create the followng Items and Depedent Item to process zabbix-agent received data from the Userparam script

Above is the list of basic Items and Dependent Item you will need to configure inside the SMTP Check zabbix Template.

The Items should have the following content and configurations:


*Name: postfix_main_proc.service
Type: Zabbix agent(active)
*Key: proc.num[master,root]
Type of Information: Numeric (unassigned)
*Update interval: 30s
Custom Intervals: Flexible
*History storage period: 90d
*Trend storage period: 365d
Show Value: as is
Applications: Postfix Checks
Populated host inventory field: -None-
Description: The item counts master daemon process that runs Postfix daemons on demand

Where the arguments pased to proc.num[] function are:
  master is the process that is being looked up for and root is the username with which the the postfix master daemon is running. If you need to adapt it for qmail or exim that shouldn't be a big deal you only have to in advance check the exact processes that are normally running on the machine
and configure a similar process check for it.

*Name: postfix_sub_procs.service_cnt
Type: Zabbix agent(active)
*Key: proc.num[,postfix]
Type of information: Numeric (unassigned)
Update Interval: 30s
*History Storage period: Storage Period 90d
*Trend storage period: Storage Period 365d
Description: The item counts master daemon processes that runs postfix daemons on demand.

Here the idea with this Item is to check the number of processes that are running with user / groupid that is postfix. Again for other SMPT different from postfix, just set it to whatever user / group 
you would like zabbix to look up for in Linux the process list. As you can see here the check for existing postfix mta process is done every 30 seconds (for more critical environments you can put it to less).

For simple zabbix use this Dependent Item is not necessery required. But as we would like to process more closely the output of the userparameter smtp script, you have to set it up.
If you want to write graphical representation by sending data to Grafana.

*Name: postfix availability check
Key: postfix_boolean_check[boolean]
Master Item: PROD SMTP Monitoring: postfix availability check
Type of Information: Numeric unassigned
*History storage period: Storage period 90d
*Trend storage period: 365d

Applications: Postfix Checks

Description: It returns boolean value of SMTP check
1 – True (SMTP is OK)
0 – False (SMTP does not responds)

Enabled: Tick

*Name: postfix availability check
*Key: smtp.check
Custom intervals: Flexible
*Update interval: 30 m
History sotrage period: Storage Period 90d
Applications: Postfix Checks
Populates host inventory field: -None-
Description: This check is testing if the SMTP relay is reachable, without actual sending an email
Enabled: Tick

4. Configure following Zabbix Triggers


Note: The severity levels you should have previosly set in Zabbix up to your desired ones.

Name: postfix master root process is not running
*Problem Expression: {PROD SMTP Monitoring:proc.num[master,root].last()}<1

OK event generation: Recovery expression
*Recovery Expression: {PROD SMTP Monitoring:proc.num[master,root].last()}>=1
Allow manual close: Tick

Description: The item counts master daemon process that runs Postfix daemon on demand.
Enabed: Tick

I would like to have an AUTO RESOLVE for any detected mail issues, if an issue gets resolved. That is useful especially if you don't have the time to put the Zabbix monitoring in Maintainance Mode during Operating system planned updates / system reboots or unexpected system reboots due to electricity power loss to the server colocated – Data Center / Rack . 

*Name: postfix master sub processes are not running
*Problem Expression: {P09 PROD SMTP Monitoring:proc.num[,postfix].last()}<1
PROBLEM event generation mode: Single
OK event closes: All problems

*Recovery Expression: {P09 PROD SMTP Monitoring:proc.num[,postfix].last()}>=1
Problem event generation mode: Single
OK event closes: All problems
Allow manual close: Tick
Enabled: Tick

Name: SMTP connectivity check
Severity: WARNING
*Expression: {PROD SMTP Monitoring:postfix_boolen_check[boolean].last()}=0
OK event generation: Expression
PROBLEM even generation mode: SIngle
OK event closes: All problems

Allow manual close: Tick
Enabled: Tick

5. Configure respective Zabbix Action



As the service is tagged with 'pci service' tag we define the respective conditions and according to your preferences, add as many conditions as you need for the Zabbix Action to take place.

Assuming that communication chain beween Zabbix Server -> Zabbix Proxy (if zabbix proxy is used) -> Zabbix Agent works correctly you should start receiving that from the userparameter script in Zabbix with the configured smtp.check userparam key every 30 minutes.

Note that this simple nc check will keep a trail records inside your /var/log/maillog for each netcat connection, so keep in mind that in /var/log/maillog on each host which has configured the SMTP Check zabbix template, you will have some records  similar to:

# tail -n 50 /var/log/maillog
2023-06-22T09:32:18.164128+02:00 lpgblu01f postfix/smtpd[2690485]: improper command pipelining after HELO from localhost[]:  MAIL FROM:\n RCPT TO:\n  QUIT\n
2023-06-22T09:32:18.208888+02:00 lpgblu01f postfix/smtpd[2690485]: 32EB02005B: client=localhost[]
2023-06-22T09:32:18.209142+02:00 lpgblu01f postfix/smtpd[2690485]: disconnect from localhost[] helo=1 mail=1 rcpt=1 quit=1 commands=4
2023-06-22T10:02:18.889440+02:00 lpgblu01f postfix/smtpd[2747269]: connect from localhost[]
2023-06-22T10:02:18.889553+02:00 lpgblu01f postfix/smtpd[2747269]: improper command pipelining after HELO from localhost[]:  MAIL FROM:\n RCPT TO:\n  QUIT\n
2023-06-22T10:02:18.933933+02:00 lpgblu01f postfix/smtpd[2747269]: E3ED42005B: client=localhost[]
2023-06-22T10:02:18.934227+02:00 lpgblu01f postfix/smtpd[2747269]: disconnect from localhost[] helo=1 mail=1 rcpt=1 quit=1 commands=4
2023-06-22T10:32:26.143282+02:00 lpgblu01f postfix/smtpd[2804195]: connect from localhost[]
2023-06-22T10:32:26.143439+02:00 lpgblu01f postfix/smtpd[2804195]: improper command pipelining after HELO from localhost[]:  MAIL FROM:\n RCPT TO:\n  QUIT\n
2023-06-22T10:32:26.186681+02:00 lpgblu01f postfix/smtpd[2804195]: 2D7F72005B: client=localhost[]
2023-06-22T10:32:26.186958+02:00 lpgblu01f postfix/smtpd[2804195]: disconnect from localhost[] helo=1 mail=1 rcpt=1 quit=1 commands=4
2023-06-22T11:02:26.924039+02:00 lpgblu01f postfix/smtpd[2860398]: connect from localhost[]
2023-06-22T11:02:26.924160+02:00 lpgblu01f postfix/smtpd[2860398]: improper command pipelining after HELO from localhost[]:  MAIL FROM:\n RCPT TO:\n  QUIT\n
2023-06-22T11:02:26.963014+02:00 lpgblu01f postfix/smtpd[2860398]: EB08C2005B: client=localhost[]
2023-06-22T11:02:26.963257+02:00 lpgblu01f postfix/smtpd[2860398]: disconnect from localhost[] helo=1 mail=1 rcpt=1 quit=1 commands=4
2023-06-22T11:32:29.145553+02:00 lpgblu01f postfix/smtpd[2916905]: connect from localhost[]
2023-06-22T11:32:29.145664+02:00 lpgblu01f postfix/smtpd[2916905]: improper command pipelining after HELO from localhost[]:  MAIL FROM:\n RCPT TO:\n  QUIT\n
2023-06-22T11:32:29.184539+02:00 lpgblu01f postfix/smtpd[2916905]: 2CF7D2005B: client=localhost[]
2023-06-22T11:32:29.184729+02:00 lpgblu01f postfix/smtpd[2916905]: disconnect from localhost[] helo=1 mail=1 rcpt=1 quit=1 commands=4



That's all folks use the :
Configuration -> Host (menu)

and assign the new SMTP check template to as many of the Linux hosts where you have setup the Userparameter script and Enjoy the new mail server monitoring at hand.

Unfreeze stucked “freezed” messages from Exim Mail server queue

June 16th, 2023


Messages are frozen when the mail server has determined it cannot do anything to deliver the message. (they can also be manually frozen).

Exim has option to set how long frozen messages are kept on the system.

On a Debian/Ubuntu based install the /etc/exim4/conf.d/main/02_exim4-config_options file has the option timeout_frozen_after = 7d. Which means messages frozen for 7 days will get expunged.

Frozen messages really shouldn't be a problem on most systems. They are often just spam messages that can't get properly delivered.

If you have to deal with freezed mails from the exim mail server, unlike postfix, where there is no "freeze" scheme but the messages just stuck in the queue and you might want to simply ask the mail server to resend failed to deliver messages once again through a simple:

# postqueue -f

With exim to ask the server to resend the freeze-d states messages there is another aproach:

It is for this reason that I am writing this post to share how you can ask the exim to resend the "frozen" messages, as on exim there is no so much straight forward way.

To find out what letters are stored in the exim queue run

# exim -bp

To unfreeze the messages a simple while loop can be written, which lists all frozen state messages and unfreezes these letters one by one in a cycle:

# exim -bp | grep -i frozen | awk '{print $3}' | while read LINE; do exim -Mt $LINE; done

Another approach to unfreeze the frozen multitude of messages which should be a bit quicker if you have to do it for a very large amount of frozen states mails is to use xargs command:

# mailq | grep frozen | awk '{print $3}' | xargs exim -v -M

Since we on exim topic in this article, for starters with Exim, here is few other useful exim queue commands, that might be beneficial if you have to deal with EXIM SMTP.

Attempting to send a mail with a specified ID

# /usr/sbin/exim -M email-id

Forcefully run another queue to execute

# /usr/sbin/exim -qf

We see the logs related to letter

# /usr/sbin/exim -Mvl messageID

To see the body of the letter

# /usr/sbin/exim -Mvb messageID

To see the beginning (header) of the letter only

# /usr/sbin/exim -Mvh messageID

Deletes the mail without sending any error messages

# /usr/sbin/exim -Mrm messageID

Shows the number of letters in the queue

# /usr/sbin/exim -bpr | grep "<" | wc -l

Shows the number of frozen mails in the queue

# /usr/sbin/exim -bpr | grep frozen | wc -l

Deletes all frozen letters

# /usr/sbin/exim -bpr | grep frozen | awk {'print $3'} | xargs exim -Mrm

To remove a message from the Exim queue

# exim -Mrm {message-id}

Remove all messages from the Exim queue

# exim -bp | awk '/^ *[0-9]+[mhd]/{print "exim -Mrm " $3}' | bash

Another way to do it:

# exim -bp | exiqgrep -i | xargs exim -Mrm

Fastest solution to delete all emails in exim queue (for less than 5 seconds) is

# cd /var/spool
# mv exim exim.old
# mkdir -p exim/input
# mkdir -p exim/msglog
# mkdir -p exim/db
# chown -R mail:mail exim
# /sbin/service exim restart

or if you have AV / AntiSpam integrated to mail server:

# cd /var/spool
# mv exim exim.old
# mkdir -p exim/db
# mkdir -p exim/input
# mkdir -p exim/msglog
# mkdir -p exim/scan
# chown -R mail:mail exim
# /sbin/service exim restart

Deletes the entire exim queue

# /usr/sbin/exim -qff

Install specific zabbix-agent version / Downgrade Zabbix Agent client to exact preferred old RPM version on CentOS / Fedora / RHEL Linux from repo

June 7th, 2023



In below article, I'll give you the short Update zabbix procedure to specific version release, if you need to have it running in tandem with rest of zabbix infra, as well as expain shortly how to downgrade zabbix version to a specific release number
to match your central zabbix-serveror central zabbix proxies.

The article is based on personal experience how to install / downgrade the specific zabbuix-agent  release on RPM based distros.
I know this is pretty trivial stuff but still, hope this might be useful to some sysadmin out there thus I decided to quickly blog it.


1. Prepare backup of zabbix_agentd.conf

cp -rpf /etc/zabbix/zabbix_agentd.conf /home/your-user/zabbix_agentd.conf.bak.$(date +"%b-%d-%Y")


2. Create zabbix repo source file in yum.repos.d directory

cd /etc/yum.repos.d/
vim zabbix.repo 



name=Zabbix 5.0 repo





3. Update zabbix-agent to a specific defined version

yum search zabbix-agent –enablerepo zabbix-5.0

To update zabbix-agent for RHEL 7.*

# yum install zabbix-agent-5.0.34-1.el7.x86_64

For RHEL 8.*

# yum install zabbix-agent-5.0.34-1.el8.x86_64

4. Restart zabbix-agentd and check its status to make sure it works correctly

systemctl status zabbix-agentd
systemctl restart zabbix-agentd
# systemctl status zabbix-agentd

Go to zabbix-server WEB GUI interface and check that data is delivered as normally in Latest Data for the host fom recent time, to make sure host monitoring is continuing flawlessly as before change.

NB !: If yum use something like versionlock is enabled remove the versionlock for package and update then, otherwise it will (weirldly look) look like the package is missing.
I'm saying that because I've hit this issue and was wondering why i cannot install the zabbix-agent even though the version is listed, available and downloadable from the repository.

5. Downgrade agent-client to specific version (Install old version of Zabbix from Repo)

Sometimes by mistake you might have raised the Zabbix-agent version to be higher release than the zabbix-server's version and thus breach out the Zabbix documentation official recommendation to keep
up the zabbix-proxy, zabbix-server and zabbix-agent at the exactly same version major and minor version releases. 

If so, then you would want to decrease / downgrade the version, to match your Zabbix overall infrastructure exact version for each of Zabbix server -> Zabbix Proxy server -> Agent clients.

To downgrade the version, I prefer to create some backups, just in case for all /etc/zabbix/ configurations and userparameter scripts (from experience this is useful as sometimes some RPM binary update packages might cause /etc/zabbix/zabbix_agentd.conf file to get overwritten. To prevent from restoring zabbix_agentd.conf from your most recent backup hence, I prefer to just crease the zabbix config backups manually.

# cd /root

# mkdir -p /root/backup/zabbix-agent 

# tar -czvf zabbix_agent.tar.gz /etc/zabbix/

# tar -xzvf zabbix_agent.tar.gz 

Then list the available installable zabbix-agent versions

[root@sysadminshelp:~]# yum –showduplicates list zabbix-agent
Заредени плъгини: fastestmirror
Determining fastest mirrors
 * base:
 * epel:
 * extras:
 * remi:
 * remi-php74:
 * remi-safe:
 * updates:
Инсталирани пакети
zabbix-agent.x86_64                                                     5.0.30-1.el7                                                     @zabbix
Налични пакети
zabbix-agent.x86_64                                                     5.0.0-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.1-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.2-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.3-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.4-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.5-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.6-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.7-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.8-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.9-1.el7                                                      zabbix
zabbix-agent.x86_64                                                     5.0.10-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.11-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.12-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.13-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.14-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.15-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.16-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.17-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.18-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.19-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.20-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.21-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.22-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.23-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.24-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.25-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.26-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.27-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.28-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.29-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.30-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.31-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.32-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.33-1.el7                                                     zabbix
zabbix-agent.x86_64                                                     5.0.34-1.el7                                                     zabbix


Next lets install the most recent zabbix-versoin from the CentOS repo, which for me as of time of writting this article is 5.0.34.

# yum downgrade -y zabbix-agent-5.0.34-1.el7

# cp -rpf /root/backup/zabbix-agent/etc/zabbix/zabbix_agentd.conf /etc/zabbix/

# systemctl start zabbix-agent.service

# systemctl enable  zabbix-agent.service

# zabbix_agentd -V
zabbix_agentd (daemon) (Zabbix) 5.0.30
Revision 2c96c38fb4b 28 November 2022, compilation time: Nov 28 2022 11:27:43

Copyright (C) 2022 Zabbix SIA
License GPLv2+: GNU GPL version 2 or later <>.
This is free software: you are free to change and redistribute it according to
the license. There is NO WARRANTY, to the extent permitted by law.

This product includes software developed by the OpenSSL Project
for use in the OpenSSL Toolkit (

Compiled with OpenSSL 1.0.1e-fips 11 Feb 2013
Running with OpenSSL 1.0.1e-fips 11 Feb 2013


That's all folks you should be at your custom selected preferred version of zabbix-agent.
Enjoy ! 🙂

IPFilter firewall basics use for Adding / Removing and Cloning firewall rules

June 1st, 2023


Linux users have most definitely used Netfilter (the older from us might remember and have used ipchains) and rest
should know well or at least partially tried iptables or if you have digged into Linux firewalls more professionally, might have tried nftables
and the newer firewalld (firewall-cmd) that is the standard nowadays in CentOS / Fedora and RHEL (again an abstraction over iptables.).
On Debian firewall is organized around custom shell scripts that deal with iptables chains, or if on Ubuntu perhaps you have tried UFW (The Uncomplicated Firewall)
frontend program for managing firewalls again with iptables. For the lazy ones UFW even has another GUI frontend called Gufw (intended to be easy, intuitive,
graphical user interface for managing Uncomlicated firewall.

Different Linux distributions do use a different set of firewall mechanisms preconfigure but there are other firewall solutions on other Unixes such as ipfilter.
That historically were heavily used that is worthy mentioning and if you happen to pop-up working as a network guy inside some large corporations you might face it.

IPFilter (commonly referred to as ipf) is an open-source software package that provides firewall services and network address translation (NAT) for many Unix-like operating systems.
The author and software maintainer is Darren Reed. IPFilter supports both IPv4 and IPv6 protocols, and is a stateful firewall.
IPFilter is delivered with FreeBSD, NetBSD, Solaris 10 & 11, illumos, OpenIndiana and HP-UX.
It used to be a part of OpenBSD, but it was removed by Theo de Raadt in May 2001 due to problems with its license.
It was subsequently replaced in OpenBSD by PF, which was developed by OpenBSD's own developers.
DragonFly BSD removed its support for IPFilter in May 2011.

IPFilter can be installed as a runtime-loadable kernel module or directly incorporated into the operating system kernel, depending on the specifics of each kernel and user preferences.
The software's documentation recommends the module approach, if possible.

Here are some commands for displaying, changing and distributing IP filters with ipfilter.
It will be mostly useful, if you happen to have some obsolete OS infrastructure or OpenBSD.

The commands given below are to add / remove and activate rules on machine with ipfilter:

# ipfilter –clone
# ipfilter –save
# ipfilter –activate
# ipfilter -addrule
# ipfilter -delrule
# help ipfilter

1. Check ipfilter current config

# ipfilter –show
Name: default_ipv4, Type: ipv4, State: active
Rule    Source IP                               Protocol   Dest Port   Action
1     any                                            tcp       22     permit
2     any                                            tcp       23     permit
3     any                                            tcp       80     permit
4     any                                            tcp      443     permit
5     any                                            udp      161     permit
6     any                                            udp      123     permit
7     any                                            tcp      600 – 1023     permit
8     any                                            udp      600 – 1023     permit
Name: default_ipv6, Type: ipv6, State: active
Rule    Source IP                               Protocol   Dest Port   Action
1     any                                            tcp       22     permit
2     any                                            tcp       23     permit
3     any                                            tcp       80     permit
4     any                                            tcp      443     permit
5     any                                            udp      161     permit
6     any                                            udp      123     permit
7     any                                            tcp      600 – 1023     permit
8     any                                            udp      600 – 1023     permit
Name: default_ipv4_new, Type: ipv4, State: defined
Rule    Source IP                               Protocol   Dest Port   Action
1     any                                            tcp       22     permit
2     any                                            tcp       23     permit
3     any                                            tcp       80     permit
4     any                                            tcp      443     permit
5     any                                            udp      161     permit
6     any                                            udp      123     permit
7     any                                            tcp      600 – 1023     permit
8     any                                            udp      600 – 1023     permit

2. Clone and activate ipfilter configuration

# ipfilter –clone default_ipv4_new -from default_ipv4
# ipfilter –activate default_ipv4_new
# ipfilter –show
Name: default_ipv4, Type: ipv4, State: defined
Rule    Source IP                               Protocol   Dest Port   Action
1     any                                            tcp       22     permit
2     any                                            tcp       23     permit
3     any                                            tcp       80     permit
4     any                                            tcp      443     permit
5     any                                            udp      161     permit
6     any                                            udp      123     permit
7     any                                            tcp      600 – 1023     permit
8     any                                            udp      600 – 1023     permit
Name: default_ipv6, Type: ipv6, State: active
Rule    Source IP                               Protocol   Dest Port   Action
1     any                                            tcp       22     permit
2     any                                            tcp       23     permit
3     any                                            tcp       80     permit
4     any                                            tcp      443     permit
5     any                                            udp      161     permit
6     any                                            udp      123     permit
7     any                                            tcp      600 – 1023     permit
8     any                                            udp      600 – 1023     permit
Name: default_ipv4_neu, Type: ipv4, State: active
Rule    Source IP                               Protocol   Dest Port   Action
1     any                                            tcp       22     permit
2     any                                            tcp       23     permit
3     any                                            tcp       80     permit
4     any                                            tcp      443     permit
5     any                                            udp      161     permit
6     any                                            udp      123     permit
7     any                                            tcp      600 – 1023     permit
8     any                                            udp      600 – 1023     permit

3. Modify cloned configuration

Lets say we would like to delete the telnet port accept traffic rule  (port 23)

# ipfilter –delrule default_ipv4_new -rule 2

To permit the rule agian

# ipfilter –addrule default_ipv4_new -rule 2 -sip any -dp 23 -proto tcp -act permit

To save the rule

# ipfilter –save default_ipv4_new                          

Install btop on Debian Linux, btop an advanced htop like monitoring for Linux to beautify your console life

May 30th, 2023


I've accidently stubmled on btop a colorful and interactive ncurses like command line utility to provide you a bunch of information about CPU / memory / disks and processes with nice console graphic in the style of Cubic Player 🙂
Those who love htop and like their consoles to be full of shiny colors, will really appreciate those nice Linux monitoring tool.
To install btop on latest current stable Debian bullseyes, you will have to install it via backports, as the regular Debian repositories does not have the tool available out of the box.

To Add backports packages support for your Debian 11:

1. Edit /etc/apt/sources.list and include following repositories


# vim /etc/apt/sources.list

deb bullseye-backports main contrib non-free
deb-src bullseye-backports main contrib non-free

2. Update the known repos list to include it


# apt update

3. Install the btop deb package from backports


# apt-cache show btop|grep -A 20 -i descrip
Description-en: Modern and colorful command line resource monitor that shows usage and stats
 btop is a modern and colorful command line resource monitor that shows
 usage and stats for processor, memory, disks, network and processes.
 btop features:
  – Easy to use, with a game inspired menu system.
  – Full mouse support, all buttons with a highlighted key is clickable
  and mouse scroll works in process list and menu boxes.
  – Fast and responsive UI with UP, DOWN keys process selection.
  – Function for showing detailed stats for selected process.
  – Ability to filter processes.
  – Easy switching between sorting options.
  – Tree view of processes.
  – Send any signal to selected process.
  – UI menu for changing all config file options.
  – Auto scaling graph for network usage.
  – Shows IO activity and speeds for disks
  – Battery meter
  – Selectable symbols for the graphs
  – Custom presets
  – And more…
  btop is written in C++ and is continuation of bashtop and bpytop.
Description-md5: 73df6c70fe01f5bf05cca0e3031c1fe2
Multi-Arch: foreign
Section: utils
Priority: optional
Filename: pool/main/b/btop/btop_1.2.7-1~bpo11+1_amd64.deb
Size: 431500
SHA256: d79e35c420a2ac5dd88ee96305e1ea7997166d365bd2f30e14ef57b556aecb36


# apt install -t bullsye-backports btop –yes

Once I installed it, I can straight use it except on some of my Linux machines, which were having a strange encoding $LANG defined, those ones spitted some errors like:

root@freak:~# btop
ERROR: No UTF-8 locale detected!
Use –utf-force argument to force start if you're sure your terminal can handle it.


To work around it simply redefine LANG variable and rerun it

# export LANG=en_US.UTF8

# btop




How to log multiple haproxy / apache / mysql instance via haproxy log-tagging / Segregating log management for multiple HAProxy instances using rsyslog

May 23rd, 2023




This article provides a guide on refining haproxy  logging mechanism by leveraging the `programname` property in rsyslog, coupled with the `log-tag` directive in haproxy.
This approach will create a granular logging setup, separating logs according to their originating services and specific custom tags, enhancing overall log readability.

Though the article is written concretely for logging multiple log streams from haproxy this can be successfully applied
for any other Linux service to log as many concrete log-tagged data streams as you prefer.


The guide focuses on tailoring the logging mechanisms for two haproxy  instances named `haproxy` and `haproxyssl`, utilizing the `programname` property in rsyslog and the `log-tag` directive in haproxy for precise log management.

The haproxy and haproxyssl instances are two separate systemd config file prepared instances.
haproxy instance is simple haproxy proxying tcp traffic in non-encrypted form, whether haproxyssl is a special instance
prepared to tunnel the incoming http traffic in ssl form. Both instances of haproxy runs as a separate processes on the server.

Here is the systemd configuration of haproxy systemd service file:

# cat /usr/lib/systemd/system/haproxy.service
Description=HAProxy Load Balancer

Environment="CONFIG=/etc/haproxy/haproxy.cfg" "PIDFILE=/run/"
ExecStartPre=/usr/sbin/haproxy -f $CONFIG -c -q $OPTIONS
ExecStart=/usr/sbin/haproxy -Ws -f $CONFIG -p $PIDFILE $OPTIONS
ExecReload=/usr/sbin/haproxy -f $CONFIG -c -q $OPTIONS
ExecReload=/bin/kill -USR2 $MAINPID


As well as the systemd service configuration for haproxyssl:

# cat /usr/lib/systemd/system/haproxyssl.service
Description=HAProxy Load Balancer

Environment="CONFIG=/etc/haproxy/haproxy_ssl_prod.cfg" "PIDFILE=/run/"
ExecStartPre=/usr/sbin/haproxyssl -f $CONFIG -c -q $OPTIONS
ExecStart=/usr/sbin/haproxyssl -Ws -f $CONFIG -p $PIDFILE $OPTIONS
ExecReload=/usr/sbin/haproxyssl -f $CONFIG -c -q $OPTIONS
ExecReload=/bin/kill -USR2 $MAINPID



Step 1: Configuring HAProxy instances with `log-tag`

To distinguish between logs from two HAProxy instances, `log-tag` directive is used to add tags to logs. This tag is used to filter these logs in rsyslog.
Modify the HAProxy configuration file in `/etc/haproxy/haproxy.*.cfg`

HAProxy Instance 1 (haproxy)

# Global settings
      log local6 debug
      log-tag      haproxy

HAProxy Instance 2 (haproxyssl)

# Global settings
    log local5 debug
    log-tag      haproxyssl


Step 2: Implementing rsyslog configuration for haproxy logs

Next, create a new rsyslog configuration file, stored in /etc/rsyslog.d/. Ensure the new configuration file ends in `.conf`

HAProxy Instance 1 (haproxy)

Now add rsyslog rules to filters logs based on the `programname` and the custom log tag:

# vi /etc/rsyslog.d/55_haproxy.conf
if $programname == 'haproxy' then /var/log/haproxy.log

HAProxy Instance 2 (haproxyssl)
# vi /etc/rsyslog.d/51_haproxy_ssl.conf
if $programname == 'haproxy_ssl' then /var/log/haproxy_ssl.log

These rules filter logs that originate from haproxy  and contain the respective string haproxy   or haproxy_ssl , directing them to their respective log files. The `& stop` directive ensures that rsyslog stops processing the log once a match is found, preventing dublication.

Finally, restart both the haproxy and rsyslog services for the changes to take effect:

# systemctl restart haproxy
# systemctl restart haproxyssl
# systemctl restart rsyslog

Reading References

haproxy:   log-tag directive

rsyslog:    rsyslogd documentation

This is a guest article originally written by: Dimitar Paskalev, guest blogging with good interesting articles is always mostly welcome