Posts Tagged ‘bin’

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Play Audio Music CDs in Linux console / terminal in the 21 Century mission hard but possible

Tuesday, July 30th, 2024


Compact discs (CD's) ain't dead yet but there easy straigh use on free operating systems Linux / FreeBSD / OpenBSD is starting to deteriorate. That is quite normal I guess, as CDs are no longer officially produced or sold for few years in America and there is no Audio CD bookstores, neither in europe and perhaps there are just few in europe, perhaps CD are used somewhere in Africa and Asia, but most modern world has officially buried them.

However as I love old stuff and I had the opportunity, I bought an old Audio CD (fake copy one 🙂 of Judas Priest Screaming for Vengence and the famous Jimi Hendrix  (Best Complilation) Experience an improvised shelf-book store selling books by a half deaf aging guy who sells books for years in Dobrich in the center.
And to remember the young years of Rock Roll wanted to play it on my very old but still kicking Lenovo Thinkpad R61 notebook (that is now 16 years old but thanksfully it still works and kicks ass with a Debian GNU / Linux 10 Buster.)

The task is very easy and as I have a Window Maker (Wmaker) on it in order to save myself an extra loading of this a kind of "archaic machine" and tried to play my CDs with everything at hand thus I tried first to play the CD in console with the good old but gold cdplay with which I have played a dozens of Audio CDs back in the days … 

# cdplay

just to find out the CD got red and started to roll but I get no sound via the Sound Card 🙁

Next thing, i assumed was the problem might be the pulseaudio process blocking the sound card to be used, preventing cdplay to be able to properly channel the sound to the sound card, that used to be quite of classical problem, if you remember, thus I tried to run the cdplay via the aoss (Wrapper script to facilitate use of alsa oss compatibility library.)

Before using oss of course i've loaded the snd-pcm-oss kernel module, to make the sound blaster be able to use the old obsolete Open Sound System.

# modprobe snd-pcm-oss

# aoss cdplay

Though that aoss trick worked for some programs that used old Open Sound System scheme to output sound, it doesn't unfortunately, at that case.
 

Strange enough my sound card is properly identified by the Debian Linux and I can play MP3 songs, as well browse videos in youtube and other Internet resources in Firefox and even the pulseaudio process that is running in the background is spitting sounds out of the Notebook Speakers.

The laptop doesn't seem to have any sound driver or Sound Card issues, as I can normally play my old .XM and .MOD  sound extension files with the good old mikmod

 

# mikmod

as well as I can even normally play MIDI audio files by using the timidity tool as well as with playmidi

# timidity HitTheLights.mid

# playmidi HitTheLights.mid


Just to proove the MIDIs can be played normally via the Sound Blaster (for a more on the topic check my previous article talking in depth about Linux and MIDI – Play Midis on Linux / Make Linux MIDI Ready for the Future – Enable embedded MIDI music to play in a Browser, Play MIDIs with VLC and howto enjoy Midis in Text Console.

Next logically to make sure, something is not wrong with audio drivers, I tried to play some music normally with, the standard console players I have played with for years on Linux mpg123 / mpg321 for reference check my Listening music in text mode in Linux console but this was no luck again …

I tried even to install the opencubicplayer ( Linux port) music player and tried to open the CD, but even though the CD can be heard to be rolling in the CD drive no sound was outputed out of the laptop speakers.

 

open-cubic-player-screenshot-on-linux

Thus to resolve tried everything at power starting from increasing any missing volumes via the aumix command, as often in the past I remember the problem in such situations is the sound volume is decreased to zero percentage or completely muted.

# aumix


aumix-with-linux-htop-screenshot-animated-gif

as well as with 

# alsamixer


Alsamixer-control-sound-volume-linux-screenshot

Nevertheless, every possible volume up volume was raised and everything looked cool as I could play normally music on machine or in a browser, the AUDIO CD Music refused to play out of the Speakers.
 

Playing the Audio CD via success with mplayer

The work around to make it play was up to a one liner with mplayer

# mplayer -cdrom-device /dev/cdrom cdda://

To easify the play of CDs I've created for my self a tiny one liner script to run it.

 

#!/bin/bash
mplayer -cdrom-device /dev/cdrom cdda://

I've called the script playcd.sh, made it executable and placed it under /usr/local/bin

# vim /usr/local/bin/playcd.sh
#!/bin/bash
mplayer -cdrom-device /dev/cdrom cdda://


# chmod +x /usr/local/bin/playcd.sh

 

Playing Audio CDs with VLC (VideoLAN Media Player)

I've vlc client installed on my Linux box, if you don't have it, do:

# apt install –yes vlc

Then roll on the CD with vlc with passing it the location to the CD, usually one of the down two pointers should work:

# vlc vcd:///dev/sr0

# vlc vcd:///dev/cdrom

If you want to loop the Tracks to play forever

# vlc –loop vcd:///dev/cdrom

By the way vlc can do much more than you think as you can even play youtube with it, for example you can try it with the Axel Folly classics Mod file, by running it like this.

# vlc https://www.youtube.com/watch?v=SlyK_elUmIw


Cheers and Enjoy CD audio on Linux  ! 🙂

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

DNS Monitoring: Check and Alert if DNS nameserver resolver of Linux machine is not properly resolving shell script. Monitor if /etc/resolv.conf DNS runs Okay

Thursday, March 14th, 2024

linux-monitor-check-dns-is-resolving-fine

If you happen to have issues occasionally with DNS resolvers and you want to keep up an eye on it and alert if DNS is not properly resolving Domains, because sometimes you seem to have issues due to network disconnects, disturbances (modifications), whatever and you want to have another mean to see whether a DNS was reachable or unreachable for a time, here is a little bash shell script that does the "trick".

Script work mechacnism is pretty straight forward as you can see we check what are the configured nameservers if they properly resolve and if they're properly resolving we write to log everything is okay, otherwise we write to the log DNS is not properly resolvable and send an ALERT email to preconfigured Email address.

Below is the check_dns_resolver.sh script:

 

#!/bin/bash
# Simple script to Monitor DNS set resolvers hosts for availability and trigger alarm  via preset email if any of the nameservers on the host cannot resolve
# Use a configured RESOLVE_HOST to try to resolve it via available configured nameservers in /etc/resolv.conf
# if machines are not reachable send notification email to a preconfigured email
# script returns OK 1 if working correctly or 0 if there is issue with resolving $RESOLVE_HOST on $SELF_HOSTNAME and mail on $ALERT_EMAIL
# output of script is to be kept inside DNS_status.log

ALERT_EMAIL='your.email.address@email-fqdn.com';
log=/var/log/dns_status.log;
TIMEOUT=3; DNS=($(grep -R nameserver /etc/resolv.conf | cut -d ' ' -f2));  

SELF_HOSTNAME=$(hostname –fqdn);
RESOLVE_HOST=$(hostname –fqdn);

for i in ${DNS[@]}; do dns_status=$(timeout $TIMEOUT nslookup $RESOLVE_HOST  $i); 

if [[ “$?” == ‘0’ ]]; then echo "$(date "+%y.%m.%d %T") $RESOLVE_HOST $i on host $SELF_HOST OK 1" | tee -a $log; 
else 
echo "$(date "+%y.%m.%d %T")$RESOLVE_HOST $i on host $SELF_HOST NOT_OK 0" | tee -a $log; 

echo "$(date "+%y.%m.%d %T") $RESOLVE_HOST $i DNS on host $SELF_HOST resolve ERROR" | mail -s "$RESOLVE_HOST /etc/resolv.conf $i DNS on host $SELF_HOST resolve ERROR";

fi

 done

Download check_dns_resolver.sh here set the script to run via a cron job every lets say 5 minutes, for example you can set a cronjob like this:
 

# crontab -u root -e
*/5 * * * *  check_dns_resolver.sh 2>&1 >/dev/null

 

Then Voila, check the log /var/log/dns_status.log if you happen to run inside a service downtime and check its output with the rest of infrastructure componets, network switch equipment, other connected services etc, that should keep you in-line to proof during eventual RCA (Root Cause Analysis) if complete high availability system gets down to proof your managed Linux servers was not the reason for the occuring service unavailability.

A simplified variant of the check_dns_resolver.sh can be easily integrated to do Monitoring with Zabbix userparameter script and DNS Check Template containing few Triggers, Items and Action if I have time some time in the future perhaps, I'll blog a short article on how to configure such DNS zabbix monitoring, the script zabbix variant of the DNS monitor script is like this:

[root@linux-server bin]# cat check_dns_resolver.sh 
#!/bin/bash
TIMEOUT=3; DNS=($(grep -R nameserver /etc/resolv.conf | cut -d ' ' -f2));  for i in ${DNS[@]}; do dns_status=$(timeout $TIMEOUT nslookup $(hostname –fqdn) $i); if [[ “$?” == ‘0’ ]]; then echo "$i OK 1"; else echo "$i NOT OK 0"; fi; done
[root@linux-server bin]#


Hope this article, will help someone to improve his Unix server Infrastucture monitoring.

Enjoy and Cheers !

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Posted in Bash Scripting, DNS, Linux, Monitoring, System Administration | No Comments »

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

Thursday, February 8th, 2024

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

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

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

Finder > Applications > Utilities and open Boot Camp Assistant.

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

2. Preparing Bootable Windows installer on Linux host machine

On DEBIAN / UBUNTU and other Deb based Linuxes

# apt install gddrescue 

On CENTOS / FEDORA :

# dnf install ddrescue

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

# fdisk -l
 

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

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

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

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

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

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

On Ubuntu Linux:

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

On Fedora Linux:

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

Launch the WoeUSB-ng program :

 

$ python3 /usr/local/bin/woeusbgui

 

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

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

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


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

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

Enjoy your new personal Spy OS ! 🙂

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Posted in Curious Facts, Educational, Mac OS X, System Administration, Windows | No Comments »

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

Tuesday, January 30th, 2024

Zabbix_arp-network-incomplete-check-logo.svg

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

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

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

1. Create  userparamater_arp_gw_check.conf Zabbix script
 

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

 

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

 

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

You can download the check_gw_arp.sh here.

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

3. Create New Zabbix Template for ARP incomplete monitoring
 

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

Create Application 

*Name
Default Gateway ARP state

4. Create Item and Dependent Item 
 

Create Zabbix Item and Dependent Item like this

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

 

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

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


5. Create Trigger to trigger WARNING or whatever you like
 

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


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

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


6. Create Zabbix Action to notify via Email etc.
 

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

 

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

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

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Posted in Linux, Monitoring, System Administration, Zabbix | No Comments »

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

Thursday, August 24th, 2023

password-expiry-linux-tux-logo-script-picture-how-to-notify-if-password-expires-on-unix

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 user_passwd_expire.sh that will report the user

# vim  /usr/local/bin/user_passwd_expire.sh

#!/bin/bash

# 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
alert_email='alerts@pc-freak.net';
# the users that are admins added to belong to this group
admin_group="admins";
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”]="abc@fqdn.com"
#    [“cba”]="bca@fqdn.com"
    [“lachezar”]="lachezar.user@gmail.com"
    [“georgi”]="georgi@fqdn-mail.com"
    [“acct3”]="acct3@fqdn-mail.com"
    [“acct4”]="acct4@fqdn-mail.com"
    [“acct5”]="acct5@fqdn-mail.com"
    [“acct6”]="acct6@fqdn-mail.com"
#    [“acct7”]="acct7@fqdn-mail.com"
#    [“acct8”]="acct8@fqdn-mail.com"
#    [“acct9”]="acct9@fqdn-mail.com"
)

declare -A days

while IFS="=" read -r person day ; do
  days[“$person”]="$day"
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]}";
     tmp=${days[$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)) )); 
     then
         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));
     then
#          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 ));
        then
             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;
        fi
     fi  
done
 


To make the script notify about expiring user accounts, place the script under some directory lets say /usr/local/bin/user_passwd_expire.sh 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/user_passwd_expire.sh >/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"
2023-11-22


Ideas for user_passwd_expire.sh 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 []: georgi@fqdn-mail.com
Office Phone []: 
Home Phone []: 

Password: 

[root@server test]# finger georgi
Login: georgi                       Name: georgi
Directory: /home/georgi                   Shell: /bin/bash
Office: georgi@fqdn-mail.com
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 ! 🙂

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Posted in Bash Scripting, Educational, Linux, Linux and FreeBSD Desktop, Security, System Administration | 3 Comments »

Zabbix: Monitor Linux rsyslog configured central log server is rechable with check_log_server_status.sh userparameter script

Wednesday, June 8th, 2022

zabbix-monitor-central-log-server-is-reachable-from-host-with-a-userparamater-script-zabbix-logo

On modern Linux OS servers on Redhat / CentOS / Fedora and Debian based distros log server service is usually running on the system  such as rsyslog (rsyslogd) to make sure the logging from services is properly logged in separate logs under /var/log.

A very common practice on critical server machines in terms of data security, where logs produced by rsyslog daermon needs to be copied over network via TCP or UDP protocol immediately is to copy over the /var/log produced logs to another configured central logging server. Then later every piece of bit generated by rsyslogd could be  overseen by a third party auditor person and useful for any investigation in case of logs integrity is required or at worse case if there is a suspicion that system in question is hacked by a malicious hax0r and logs have been "cleaned" up from any traces leading to the intruder (things usually done locally by hackers) or by any automated script exploit tools since yesr.

This doubled logging of system events to external log server  ipmentioned is very common practice by companies to protect their log data and quite useful for logs to be recovered easily later on from the central logging server machine that could be also setup for example to use rsyslogd to receive logs from other Linux machines in circumstances where some log disappears just like that (things i've seen happen) for any strange reason or gets destroyed by the admins mistake locally on machine / or by any other mean such as filesystem gets damaged. a very common practice by companies to protect their log data.  

Monitor remote logging server is reachable with userparameter script

Assuming that you already have setup a logging from the server hostname A towards the Central logging server log storepool and everything works as expected the next logical step is to have at least some basic way to monitor remote logging server configured is still reachable all the time and respectively rsyslog /var/log/*.* logs gets properly produced on remote side for example with something like a simple TCP remote server port check and reported in case of troubles in zabbix.

To solve that simple task for company where I'm employed, I've developed below check_log_server_status.sh:
 

#!/bin/bash
# @@ for TCP @ for UDP
# check_log_server_status.sh Script to check if configured TCP / UDP logging server in /etc/rsyslog.conf is rechable
# report to zabbix
DELIMITER='@@';
GREP_PORT='5145';
CONNECT_TIMEOUT=5;

PORT=$(grep -Ei "*.* $DELIMITER.*:$GREP_PORT" /etc/rsyslog.conf|awk -F : '{ print $2 }'|sort -rn |uniq);

#for i in $(grep -Ei "*.* $DELIMITER.*:$GREP_PORT" /etc/rsyslog.conf |grep -v '\#'|awk -F"$DELIMITER" '{ print $2 }' | awk -F ':' '{ print $1 }'|sort -rn); do
HOST=$(grep -Ei "*.* $DELIMITER.*:$GREP_PORT" /etc/rsyslog.conf |grep -v '\#'|awk -F"$DELIMITER" '{ print $2 }' | awk -F ':' '{ print $1 }'|sort -rn)

# echo $PORT

if [[ ! -z $PORT ]] && [[ ! -z $HOST ]]; then
SSH_RETURN=$(/bin/ssh $HOST -p $PORT -o ConnectTimeout=$CONNECT_TIMEOUT 2>&1);
else
echo "PROBLEM Port $GREP_PORT not defined in /etc/rsyslog.conf";
fi

##echo SSH_RETURN $SSH_RETURN;
#exit 1;
if [[ $(echo $SSH_RETURN |grep -i ‘Connection timed out during banner exchange’ | wc -l) -eq ‘1’ ]]; then
echo "rsyslogd $HOST:$PORT OK";
fi

if [[ $(echo $SSH_RETURN |grep -i ‘Connection refused’ | wc -l) -eq ‘1’ ]]; then
echo "rsyslogd $HOST:$PORT PROBLEM";
fi

#sleep 2;
#done


You can download a copy of the script check_log_server_status.sh here

Depending on the port the remote rsyslogd central logging server is using configure it in the script with respective port through the DELIMITER='@@', GREP_PORT='5145', CONNECT_TIMEOUT=5 values.

The delimiter is setup as usually in /etc/rsyslog.conf this the remote logging server for TCP IP is configured with @@ prefix to indicated TCP mode should be used.

Below is example from /etc/rsyslog.conf of how the rsyslogd server is configured:

[root@Server-hostA /root]# grep -i @@ /etc/rsyslogd.conf
# central remote Log server IP / port
*.* @@10.10.10.1:5145

To use the script on a machine, where you have a properly configured zabbix-agentd service host connected and reporting data to a zabbix-server monitoring server.

1. Set up the script under /usr/local/bin/check_log_server_status.sh

[root@Server-hostA /root ]# vim /usr/local/bin/check_log_server_status.sh
…

[root@Server-hostA /root ]# chmod +x /usr/local/bin/check_log_server_status.sh

2. Prepare userparameter_check_log_server.conf with log_server.check Item key

[root@Server-hostA zabbix_agentd.d]# cat userparameter_check_log_server.conf 
UserParameter=log_server.check, /usr/local/bin/check_log_server_status.sh

3. Set in Zabbix some Item such as on below screenshot

 

check-log-server-status-screenshot-linux-item-zabbix.png4. Create a Zabbix trigger 

check-log-server-status-trigger-logserver-is-unreachable-zabbix


The redded hided field in Expression field should be substituted with your actual hostname on which the monitor script will run.

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Posted in Monitoring, System Administration, Various, Zabbix | No Comments »

Get dmesg command kernel log report with human date / time timestamp on older Linux distributions

Friday, June 18th, 2021

how-to-get-dmesg-human-readable-timestamp-kernel-log-command-linux-logo

If you're a sysadmin you surely love to take a look at dmesg kernel log output. Usually on many Linux distributions there is a setup that dmesg keeps logging to log files /var/log/dmesg or /var/log/kern.log. But if you get some inherited old Linux servers it is quite possible that the previous machine maintainer did not enable the output of syslog to get logged in /var/log/{dmesg,kern.log,kernel.log}  or even have disabled the kernel log for some reason. Even though that in dmesg output you might find some interesting events reporting issues with Hard drives on its way to get broken / a bad / reads system processes crashing or whatever of other interesting information that could help you prevent severe servers downtimes or problems earlier but due to an old version of Linux distribution lets say Redhat 5 / Debian 6 or old CentOS / Fedora, the version of dmesg command shipped does not support the '-T' option that is present in util-linux package shipped with newer versions of  Redhat 7.X  / 8.X / SuSEs etc.  

 -T, –ctime
              Print human readable timestamps.  The timestamp could be inaccurate!

To illustrate better what I mean, here is an example from the non-human readable timestamp provided by older dmesg command

root@web-server~:# dmesg |tail -n 5
[4505913.361095] hid-generic 0003:1C4F:0002.000E: input,hidraw1: USB HID v1.10 Device [SIGMACHIP USB Keyboard] on usb-0000:00:1d.0-1.3/input1
[4558251.034024] Process accounting resumed
[4615396.191090] r8169 0000:03:00.0 eth1: Link is Down
[4615397.856950] r8169 0000:03:00.0 eth1: Link is Up – 100Mbps/Full – flow control rx/tx
[4644650.095723] Process accounting resumed

Thanksfully using below few lines of shell or perl scripts the dmesg -T  functionality could be added to the system , so you can easily get the proper timestamp out of the obscure default generated timestamp in the same manner as on newer distros.

Here is how to do with it with bash script:

#!/bin/sh paste in .bashrc and use dmesgt to get human readable timestamp
dmesg_with_human_timestamps () {
    FORMAT="%a %b %d %H:%M:%S %Y"

 

    now=$(date +%s)
    cputime_line=$(grep -m1 "\.clock" /proc/sched_debug)

    if [[ $cputime_line =~ [^0-9]*([0-9]*).* ]]; then
        cputime=$((BASH_REMATCH[1] / 1000))
    fi

    dmesg | while IFS= read -r line; do
        if [[ $line =~ ^\[\ *([0-9]+)\.[0-9]+\]\ (.*) ]]; then
            stamp=$((now-cputime+BASH_REMATCH[1]))
            echo "[$(date +”${FORMAT}” –date=@${stamp})] ${BASH_REMATCH[2]}"
        else
            echo "$line"
        fi
    done
}

Copy the script somewhere under lets say /usr/local/bin or wherever you like on the server and add into your HOME ~/.bashrc some alias like:
 

alias dmesgt=dmesg_with_timestamp.sh


You can get a copy dmesg_with_timestamp.sh of the script from here

Or you can use below few lines perl script to get the proper dmeg kernel date / time

 

#!/bin/perl
# on old Linux distros CentOS 6.0 etc. with dmesg (part of util-linux-ng-2.17.2-12.28.el6_9.2.x86_64) etc. dmesg -T not available
# workaround is little pl script below
dmesg_with_human_timestamps () {
    $(type -P dmesg) "$@" | perl -w -e 'use strict;
        my ($uptime) = do { local @ARGV="/proc/uptime";<>}; ($uptime) = ($uptime =~ /^(\d+)\./);
        foreach my $line (<>) {
            printf( ($line=~/^\[\s*(\d+)\.\d+\](.+)/) ? ( “[%s]%s\n", scalar localtime(time – $uptime + $1), $2 ) : $line )
        }'
}


Again to make use of the script put it under /usr/local/bin/check_dmesg_timestamp.pl

alias dmesgt=dmesg_with_human_timestamps

root@web-server:~# dmesgt | tail -n 20

[Sun Jun 13 15:51:49 2021] usb 2-1.3: USB disconnect, device number 9
[Sun Jun 13 15:51:50 2021] usb 2-1.3: new low-speed USB device number 10 using ehci-pci
[Sun Jun 13 15:51:50 2021] usb 2-1.3: New USB device found, idVendor=1c4f, idProduct=0002, bcdDevice= 1.10
[Sun Jun 13 15:51:50 2021] usb 2-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[Sun Jun 13 15:51:50 2021] usb 2-1.3: Product: USB Keyboard
[Sun Jun 13 15:51:50 2021] usb 2-1.3: Manufacturer: SIGMACHIP
[Sun Jun 13 15:51:50 2021] input: SIGMACHIP USB Keyboard as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.0/0003:1C4F:0002.000D/input/input25
[Sun Jun 13 15:51:50 2021] hid-generic 0003:1C4F:0002.000D: input,hidraw0: USB HID v1.10 Keyboard [SIGMACHIP USB Keyboard] on usb-0000:00:1d.0-1.3/input0
[Sun Jun 13 15:51:50 2021] input: SIGMACHIP USB Keyboard Consumer Control as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.1/0003:1C4F:0002.000E/input/input26
[Sun Jun 13 15:51:50 2021] input: SIGMACHIP USB Keyboard System Control as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.3/2-1.3:1.1/0003:1C4F:0002.000E/input/input27
[Sun Jun 13 15:51:50 2021] hid-generic 0003:1C4F:0002.000E: input,hidraw1: USB HID v1.10 Device [SIGMACHIP USB Keyboard] on usb-0000:00:1d.0-1.3/input1
[Mon Jun 14 06:24:08 2021] Process accounting resumed
[Mon Jun 14 22:16:33 2021] r8169 0000:03:00.0 eth1: Link is Down
[Mon Jun 14 22:16:34 2021] r8169 0000:03:00.0 eth1: Link is Up – 100Mbps/Full – flow control rx/tx

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Posted in Bash Scripting, Linux, System Administration | No Comments »

How to calculate connections from IP address with shell script and log to Zabbix graphic

Thursday, March 11th, 2021

We had to test the number of connections incoming IP sorted by its TCP / IP connection state.

For example:

TIME_WAIT, ESTABLISHED, LISTEN etc.


The reason behind is sometimes the IP address '192.168.0.1' does create more than 200 connections, a Cisco firewall gets triggered and the connection for that IP is filtered out. To be able to know in advance that this problem is upcoming. a Small userparameter script is set on the Linux servers, that does print out all connections from IP by its STATES sorted out.

 

The script is calc_total_ip_match_zabbix.sh is below:

#!/bin/bash
#  check ESTIMATED / FIN_WAIT etc. netstat output for IPs and calculate total
# UserParameter=count.connections,(/usr/local/bin/calc_total_ip_match_zabbix.sh)
CHECK_IP='192.168.0.1';
f=0; 

 

for i in $(netstat -nat | grep "$CHECK_IP" | awk '{print $6}' | sort | uniq -c | sort -n); do

echo -n "$i ";
f=$((f+i));
done;
echo
echo "Total: $f"

 

root@pcfreak:/bashscripts# ./calc_total_ip_match_zabbix.sh 
1 TIME_WAIT 2 ESTABLISHED 3 LISTEN 

Total: 6

 

root@pcfreak:/bashscripts# ./calc_total_ip_match_zabbix.sh 
2 ESTABLISHED 3 LISTEN 
Total: 5


images/zabbix-webgui-connection-check1

To make process with Zabbix it is necessery to have an Item created and a Depedent Item.

 

webguiconnection-check1

webguiconnection-check1
 

webgui-connection-check2-item

images/webguiconnection-check1

Finally create a trigger to trigger alarm if you have more than or eqaul to 100 Total overall connections.


images/zabbix-webgui-connection-check-trigger

The Zabbix userparameter script should be as this:

[root@host: ~]# cat /etc/zabbix/zabbix_agentd.d/userparameter_webgui_conn.conf
UserParameter=count.connections,(/usr/local/bin/webgui_conn_track.sh)

 

Some collleagues suggested more efficient shell script solution for suming the overall number of connections, below is less time consuming version of script, that can be used for the calculation.
 

#!/bin/bash -x
# show FIN_WAIT2 / ESTIMATED etc. and calcuate total
count=$(netstat -n | grep "192.168.0.1" | awk ' { print $6 } ' | sort -n | uniq -c | sort -nr)
total=$((${count// /+}))
echo "$count"
echo "Total:" "$total"

      2 ESTABLISHED
      1 TIME_WAIT
Total: 3

 


Below is the graph built with Zabbix showing all the fluctuations from connections from monitored IP. ebgui-check_ip_graph

 

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Posted in Linux, Various, Web and CMS, Zabbix | 2 Comments »

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