Archive for November, 2020

How to add colorful random ASCII art picture and a bible verse on each SSH server login, joyout sysadmins life with cowsay, fortune, caca-utils and others

Tuesday, November 24th, 2020

Jesus-Christ-loves-the-world-ascii-art

There are pleny of console ASCII stuff out there that can make your console sysadmin boring life a little bit more funny and cherish some memories from the old times of 8 bit computers :).

One of this as I blogged earlier is cowsay and cowthink to generate a ascii picture with a cow with your custom message.
I've earlier blogged about that in my previous article Create ASCII Art Text bannners in Linux console / terminal with figlet and toilet

One of this cool things I'm using daily on my servers  is a cowsay console goodie together with a bash shell script that does visualize a random ASCII picture from a preset of pictures on each and every ssh login to my server.
The script I use is cowrand below is code:

#!/bin/bash
# cowsay pix randomizer by hip0
# it shows random ascii from the cowsay prog during logging. :]
a=0
b=1
cowrand='/etc/cowrand';
dir='/usr/share/cowsay/cows';
var=`ls -1 $dir | wc -l | awk '{ print $1}'`
#RANGE=$var
number=$RANDOM
let "number %= $var"
var1=`ls -1 $dir | head -n $number | tail -n 1 | head -n 1`
if [ -z “$var1” ]; then
$cowrand;
else
/usr/bin/cowsay -f $var1 Welc0m3 t0 pC-fREAK … Enj0y.
fi

 

The script is set as executable under /etc/cowrand

hipo@pcfreak:~$ ls -al /etc/cowrand
-rwxr-xr-x 1 hipo hipo 432 Nov 24 19:21 /etc/cowrand*

I've set this script to my /etc/profile to auto start on every login on my Debian Linux systems right after the comments like so:

hipo@pcfreak:~$ grep -i cowrand -A 2 -B 3 /etc/profile
# /etc/profile: system-wide .profile file for the Bourne shell (sh(1))
# and Bourne compatible shells (bash(1), ksh(1), ash(1), …).
echo '';
/etc/cowrand | lolcat
echo '';
#/usr/bin/verse

As you can see to make my life even more funnier, I've installed another fun command lolcat

lolcat-screenshot

hipo@pcfreak:~$ apt-cache show lolcat |grep -i desc -A 3
Description-en: colorful `cat`
 lolcat concatenates files like the UNIX `cat` program, but colors it for the
 lulz in a rainbow animation. Terminals with 256 colors and animations are
 supported.

Description-md5: 86f992d66ac74197cda39e0bbfcb549d
Homepage: https://github.com/busyloop/lolcat
Ruby-Versions: all
Section: games


You can think of lolcat as a standard cat command that has been made to print in colors, this gives a funny results.

cowrand-script-lolcat-os-release-how-to-make-your-linux-login-prompt-funnier

To add some spice to everything nice as a recipee for thethe creation of powerpuff girls, I've come up with a way to use fortune
console tool that uses to print quotes out of a database to use as a source a big database containing the Holy Bible books of Old and New Testament Books. The fortune prints me out a quote extract from the bible on each and every remote SSH login to my machine. The content of this bible database for fortune bible_quotes_fortune.tar.gz can be downloaded and used from here.

The command used to print out a verse from the holy bible is:
 

 

hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
For if thou refuse to let them go, and wilt hold them still,
        — Exodus 9:2
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And when the queen of Sheba heard of the fame of Solomon concerning
the name of the LORD, she came to prove him with hard questions.
        — 1 Kings 10:1
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And Shelemiah, and Nathan, and Adaiah,
        — Ezra 10:39
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
For by thee I have run through a troop: by my God have I leaped
over a wall.
        — 2 Samuel 22:30
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
Unto the place of the altar, which he had make there at the first:
and there Abram called on the name of the LORD.
        — Genesis 13:4
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And there shall dwell in Judah itself, and in all the cities thereof
together, husbandmen, and they that go forth with flocks.
        — Jeremiah 31:24
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And he hath put a new song in my mouth, even praise unto our God:
many shall see it, and fear, and shall trust in the LORD.
        — Psalms 40:3
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And Jehoshaphat made peace with the king of Israel.
        — 1 Kings 22:44
 

 

The fortune is really awesome as it reminds me often of a verses from Holy Bible I often forget, the database is using the all famous King James Bible famous as (KJB) / (KJV) from 1611 this bible version that is like a protestant standard nowadays takes its name after James VI and I (James Charles Stuart; 19 June 1566 – 27 March 1625 – King of Scotland and Ireland) who was the sponsor of KJV collection and print.

Finally after adding the /usr/games/fortune -s /usr/local/fortune/ to the beginning of /etc/profile together with cowsay and cowrand I got this beautiful and educational result that combines fun with wisdom, below is example of what you will get after you  do a remote ssh login;

 

ssh your-machine.com

cowrand-script-lolcat-os-release-how-to-make-your-linux-login-prompt-funnier_1

cowrand-script-lolcat-os-release-how-to-make-your-linux-login-prompt-funnier_2

cowrand-script-lolcat-os-release-how-to-make-your-linux-login-prompt-funnier_3

Those who have a Linux Graphical Environment desktop might also enjoy xcowsay

Another must I recommend to the text geeks is the caca-utils package which contains cool things such as aafire (cacafire)

cacaview-fire-screenshot-ascii-art

Or (Image to text converter) img2txt / cacaview (a text console picture viewer) that could give you a raw idea on how a png / jpg picture looks like (or at least the picture shapes) without a need for a GUI picture viewer such as Eye of the Gnome.

bear-for-you-picture-rose

Here is a original bear

cacaview-a-bear-for-you-picture-in-plain-text-ascii

And here is the one you'll see in cacaview 🙂
To read more about cacaview I have and its uses, check my previous article Viewing JPEG,GIF and PNG in ASCII with cacaview in Linux.
If you want to show off even more as a '1337 h4x0r' you might also show your sysadm 1337 5K!11Z to colleagues by showng them how you check weather via console (i've a separate article for how to ASCII art check colorful weather forecast via console / terminal ).

If you're too bored in your daily sys admin job, you might make some fun and take some useless effort to install ASCII Art Aquarium ASCIIQUARIUM

asciiquarium1

asciiquarium2

asciiquarium3

If you're crazy enough and want to torture your other sysadmin colleagues and a get a nice prank, you might install and set asciiquarium to auto run for their specific account on each and every login to some server until they control C or if you're a bit evil you can even set a small auto load on account login via ~/.bashrc shell script to 'Disable CTRL + C' combination 🙂
 

Of course there is plenty of other cool ASCII games and stuff. I've collected some of them by launching the Play Cool Ascii games service on my machine for ASCII art geeks to test out some ASCII games here.

 

How to fix rkhunter checking dev for suspisiocus files, solve rkhunter checking if SSH root access is allowed warning

Friday, November 20th, 2020

rkhunter-logo

On a server if you have a rkhunter running and you suddenly you get some weird Warnings for suspicious files under dev, like show in in the screenshot and you're puzzled how comes this happened as so far it was not reported before the regular package patching update conducted …

root@haproxy-server ~]# rkhunter –check

rkhunter-warn-screenshot

To investigate further I've checked rkhunter produced log /var/log/rkhunter.log for a verobose message and found more specifics there on what is the exact files which rkhunter finds suspicious.
To further investigate what exactly are this suspicious files for or where, they're used for something on the system or in reality it is a hacker who hacked our supposibly PCI compliant system,
I've used the good old fuser command which is capable to show which system process is actively using a file. To have fuser report for each file from /var/log/rkhunter.log with below shell loop:

[root@haproxy-server ~]#  for i in $(tail -n 50 /var/log/rkhunter/rkhunter.log|grep -i /dev/shm|awk '{ print $2 }'|sed -e 's#:##g'); do fuser -v $i; done
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1851-27-f1sTlC/qb-request-cpg-header:
                     root       1783 ….m corosync
                     hacluster   1851 ….m attrd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-26-Znk1UM/qb-event-quorum-data:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-26-Znk1UM/qb-event-quorum-header:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-26-Znk1UM/qb-response-quorum-data:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-26-Znk1UM/qb-response-quorum-header:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-26-Znk1UM/qb-request-quorum-data:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-26-Znk1UM/qb-request-quorum-header:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-25-oCdaKX/qb-event-cpg-data:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-25-oCdaKX/qb-event-cpg-header:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-25-oCdaKX/qb-response-cpg-data:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-25-oCdaKX/qb-response-cpg-header:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-25-oCdaKX/qb-request-cpg-data:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-25-oCdaKX/qb-request-cpg-header:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-24-GKyj3l/qb-event-cfg-data:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-24-GKyj3l/qb-event-cfg-header:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-24-GKyj3l/qb-response-cfg-data:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-24-GKyj3l/qb-response-cfg-header:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-24-GKyj3l/qb-request-cfg-data:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd
                     BEN.        PID ZUGR.  BEFEHL
/dev/shm/qb-1783-1844-24-GKyj3l/qb-request-cfg-header:
                     root       1783 ….m corosync
                     root       1844 ….m pacemakerd


As you see from the output all the /dev/shm/qb/ files in question are currently opened by the corosync / pacemaker and necessery for proper work of the haproxy cluster processes running on the machines.
 

How to solve the /dev/ suspcisios files rkhunter warning?

To solve we need to tell rkhunter not check against this files this is done via  /etc/rkhunter.conf first I thought this is done by EXISTWHITELIST= but then it seems there is  a special option for rkhunter whitelisting /dev type of files only ALLOWDEVFILE.

Hence to resolve the warning for the upcoming planned early PCI audit and save us troubles we had to add on running OS which is CentOS Linux release 7.8.2003 (Core) in /etc/rkhunter.conf

ALLOWDEVFILE=/dev/shm/qb-*/qb-*

Re-run

# rkhunter –check

and Voila, the warning should be no more.

rkhunter-check-output

Another thing is on another machine the warnings produced by rkhunter were a bit different as rkhunter has mistakenly detected the root login is enabled where in reality PermitRootLogin was set to no in /etc/ssh/sshd_config

rkhunter-warning

As the problem was experienced on some machines and on others it was not.
I've done the standard boringconfig comparison we sysadmins do to tell
why stuff differs.
The result was on first machine where we had everything working as expected and
PermitRootLogin no was recognized the correct configuration was:

— SNAP —
#ALLOW_SSH_ROOT_USER=no
ALLOW_SSH_ROOT_USER=unset
— END —

On the second server where the problem was experienced the values was:

— SNAP —
#ALLOW_SSH_ROOT_USER=unset
ALLOW_SSH_ROOT_USER=no
— END —

Note that, the warning produced regarding the rsyslog remote logging is allowed is perfectly fine as, we had enabled remote logging to a central log server on the machines, this is done with:

This is done with config options under /etc/rsyslog.conf

# Configure Remote rsyslog logging server
*.* @remote-logging-server.com:514
*.* @remote-logging-server.com:514

How to backup Outlook Mailbox / Export Exchange Mail backup to .pst

Tuesday, November 17th, 2020

pst-outlook-exchange-windows-logo

In the corporate world most of us are forced to use as a desktop environment some kind of Windows version 7 / 8 / 10  version with Outlook configured to use Microsoft Exchange MailServer mailbox set to use POP3 or IMAP account.
Sometimes for new employees for Knowledge transfer purposes having a backup copy of some employee who was laid off or as most of the times has left the company for a better position or simply due to boredom.

Even just for backup purposes in case if by mistake you have deleted some mails out of your mailbox it is useful thing to create a Mailbox backup of whole mail address data especially as with time the amount of Emails grows to many, many thousand of emails year by year and under some circumstances where you have a Mailbox data Limit to up to lets say 4 Gigabytes per mailbox it is useful to periodically clean up old mails, but for the historical reference to create a backup of old email.

Even at some times it is useful to create a whole backup of mailbox every year and then delete the content of Mail data for this year from Outlook.

Export of mail data in Outlook configured email is exported to .PST file format – [ MS-PST ]: Outlook Personal Folders.

Each Personal Folders File (.PST) represents a Message store that contains an arbitrary hierarchy of Folder objects, which contains Message objects, which can contain Attachment objects. Information about Folder objects, Message objects, and Attachment objects are stored in properties, which collectively contain all of the information about the particular item.

If you want to back up the message folders locally to work PC (in addition to keeping them on the Exchange server), you can automatically move or delete older items with AutoArchive (feature of Outlook) or export the items to .pst file that you can restore later as needed and use by importing.

So how to backup / export your Email correspondence to .PTS?

1. Select File -> Open & Export -> Import/Export

outlook-backup-emails-to-pst-file-howto-1

2. Select Export to a file, and then select Next.

outlook-backup-emails-to-pst-file-howto-2

3. Select Outlook Data File (.pst), and select Next.

outlook-backup-emails-to-pst-file-howto-3

4. Select the mail folder you want to back up and select Next.

outlook-backup-emails-to-pst-file-howto-4

5. Choose a location and name for your backup file, and then select Finish.

outlook-backup-emails-to-pst-file-howto-7

To ensure no one has access to your .pst files, after finish you'll be prompted to enter and confirm a password (or if you don't want pass leave pass field as empty), and then select OK.

The produced .pst file will be stored by default under C:\Users\Username\Documents\Outlook Files.

The messages that you keep in a .pst file are no different from other standard messages in outlook. You can forward, reply, or search through the stored messages as you do with other messages.
 

How to install and use memcached on Debian GNU / Linux to share php sessions between DNS round robined Apache webservers

Monday, November 9th, 2020

apache-load-balancing-keep-persistent-php-sessions-memcached-logo

Recently I had to come up with a solution to make A bunch of websites hosted on a machine to be high available. For the task haproxy is one of logical options to use. However as I didn't wanted to set new IP addresses and play around to build a cluster. I decided the much more simplistic approach to use 2 separate Machines each running Up-to-date same version of Apache Webserver as front end and using a shared data running on Master-to-Master MySQL replication database as a backend. For the load balancing itself I've used a simple 2 multiple DNS 'A' Active records, configured via the Bind DNS name server an Round Robin DNS load balancing for each of the domains, to make them point to the the 2 Internet IP addresses (XXX.XXX.XXX.4 and YYY.YYY.YYY.5) each configured on the 2 Linux servers eth0.

So far so good, this setup worked but immediately, I've run another issue as I found out the WordPress and Joomla based websites's PHP sessions are lost, as the connectivity by the remote client browser reaches one time on XXX…4 and one time on YYY…4 configured listerner on TCP port 80 and TCP p. 443. In other words if request comes up to Front end Apache worker webserver 1 with opened channel data is sent back to Client Browser and the next request is sent due to the other IP resolved by the DNS server to come to Apache worker webserver 2 of course webserver 2 has no idea about this previous session data and it gets confused and returns soemething like a 404 or 500 or any other error … not exciting really huh …

I've thought about work around and as I didn't wanted to involve thirty party stuff as Privoxy / Squid  / Varnish / Polipo etc. just as that would add extra complexity as if I choose to use haproxy from the beginning, after short investigation came to a reason to use memcached as a central PHP sessions storage.

php-memcached-apache-workers-webbrowser-keep-sessions-diagram
 

Why I choose memcached ?


Well it is relatively easy to configure, it doesn't come with mambo-jambo unreadable over-complicated configuration and the time to configure everything is really little as well as the configuration is much straight forward, plus I don't need to occupy more IP addresses and I don't need to do any changes to the already running 2 WebServers on 2 separate Linux hosts configured to be reachable from the Internet.
Of course using memcached is not a rock solid and not the best solution out there, as there is risk that if a memcached dies out for some reason all sessions stored in are lost as they're stored only in volatile memory, as well as there is a drawback that if a communication was done via one of the 2 webservers and one of them goes down sessions that were known by one of Apache's workers disappears.

So let me proceed and explain you the steps to take to configure memcached as a central session storage system.
 

1. Install memcached and php-memcached packages


To enable support for memcached besides installing memcached daemon, you need to have the php-memcached which will provide the memcached.so used by Apache loaded php script interpretter module.

On a Debian / Ubuntu and other deb based GNU / Linux it should be:

webserver1:~# apt-get install memcached php-memcached

TO use php-memcached I assume Apache and its support for PHP is already installed with lets say:
 

webserver1:~# apt-get install php libapache2-mod-php php-mcrypt


On CentOS / RHEL / Fedora Linux it is a little bit more complicated as you'll need to install php-pear and compile the module with pecl

 

[root@centos ~]# yum install php-pear

[root@centos ~]# yum install php-pecl-memcache


Compile memcache

[root@centos ~]# pecl install memcache

 

2. Test if memcached is properly loaded in PHP


Once installed lets check if memcached service is running and memcached support is loaded as module into PHP core.

 

webserver1:~# ps -efa  | egrep memcached
nobody   14443     1  0 Oct23 ?        00:04:34 /usr/bin/memcached -v -m 64 -p 11211 -u nobody -l 127.0.0.1 -l 192.168.0.1

root@webserver1:/# php -m | egrep memcache
memcached


To get a bit more verbose information on memcache version and few of memcached variable settings:

root@webserver1:/# php -i |grep -i memcache
/etc/php/7.4/cli/conf.d/25-memcached.ini
memcached
memcached support => enabled
libmemcached version => 1.0.18
memcached.compression_factor => 1.3 => 1.3
memcached.compression_threshold => 2000 => 2000
memcached.compression_type => fastlz => fastlz
memcached.default_binary_protocol => Off => Off
memcached.default_connect_timeout => 0 => 0
memcached.default_consistent_hash => Off => Off
memcached.serializer => php => php
memcached.sess_binary_protocol => On => On
memcached.sess_connect_timeout => 0 => 0
memcached.sess_consistent_hash => On => On
memcached.sess_consistent_hash_type => ketama => ketama
memcached.sess_lock_expire => 0 => 0
memcached.sess_lock_max_wait => not set => not set
memcached.sess_lock_retries => 5 => 5
memcached.sess_lock_wait => not set => not set
memcached.sess_lock_wait_max => 150 => 150
memcached.sess_lock_wait_min => 150 => 150
memcached.sess_locking => On => On
memcached.sess_number_of_replicas => 0 => 0
memcached.sess_persistent => Off => Off
memcached.sess_prefix => memc.sess.key. => memc.sess.key.
memcached.sess_randomize_replica_read => Off => Off
memcached.sess_remove_failed_servers => Off => Off
memcached.sess_sasl_password => no value => no value
memcached.sess_sasl_username => no value => no value
memcached.sess_server_failure_limit => 0 => 0
memcached.store_retry_count => 2 => 2
Registered save handlers => files user memcached


Make sure /etc/default/memcached (on Debian is enabled) on CentOS / RHELs this should be /etc/sysconfig/memcached

webserver1:~# cat default/memcached 
# Set this to no to disable memcached.
ENABLE_MEMCACHED=yes

As assured on server1 memcached + php is ready to be used, next login to Linux server 2 and repeat the same steps install memcached and the module and check it is showing as loaded.

Next place under some of your webservers hosted websites under check_memcached.php below PHP code
 

<?php
if (class_exists('Memcache')) {
    $server = 'localhost';
    if (!empty($_REQUEST[‘server’])) {
        $server = $_REQUEST[‘server’];
    }
    $memcache = new Memcache;
    $isMemcacheAvailable = @$memcache->connect($server);

    if ($isMemcacheAvailable) {
        $aData = $memcache->get('data');
        echo '<pre>';
        if ($aData) {
            echo '<h2>Data from Cache:</h2>';
            print_r($aData);
        } else {
            $aData = array(
                'me' => 'you',
                'us' => 'them',
            );
            echo '<h2>Fresh Data:</h2>';
            print_r($aData);
            $memcache->set('data', $aData, 0, 300);
        }
        $aData = $memcache->get('data');
        if ($aData) {
            echo '<h3>Memcache seem to be working fine!</h3>';
        } else {
            echo '<h3>Memcache DOES NOT seem to be working!</h3>';
        }
        echo '</pre>';
    }
}

if (!$isMemcacheAvailable) {
    echo 'Memcache not available';
}

?>


Launch in a browser https://your-dns-round-robined-domain.com/check_memcached.php, the browser output should be as on below screenshot:

check_memcached-php-script-website-screenshot

3. Configure memcached daemons on both nodes

All we need to set up is the listen IPv4 addresses

On Host Webserver1
You should have in /etc/memcached.conf

-l 127.0.0.1
-l 192.168.0.1

webserver1:~# grep -Ei '\-l' /etc/memcached.conf 
-l 127.0.0.1
-l 192.168.0.1


On Host Webserver2

-l 127.0.0.1
-l 192.168.0.200

 

webserver2:~# grep -Ei '\-l' /etc/memcached.conf
-l 127.0.0.1
-l 192.168.0.200

 

4. Configure memcached in php.ini

Edit config /etc/php.ini (on CentOS / RHEL) or on Debians / Ubuntus etc. modify /etc/php/*/apache2/php.ini (where depending on the PHP version you're using your php location could be different lets say /etc/php/5.6/apache2/php.ini):

If you wonder where is the php.ini config in your case you can usually get it from the php cli:

webserver1:~# php -i | grep "php.ini"
Configuration File (php.ini) Path => /etc/php/7.4/cli
Loaded Configuration File => /etc/php/7.4/cli/php.ini

 

! Note: That on on PHP-FPM installations (where FastCGI Process Manager) is handling PHP requests,path would be rather something like:
 

/etc/php5/fpm/php.ini

in php.ini you need to change as minimum below 2 variables
 

session.save_handler =
session.save_path =


By default session.save_path would be set to lets say session.save_path = "

/var/lib/php7/sessions"


To make php use a 2 central configured memcached servers on webserver1 and webserver2 or even more memcached configured machines set it to look as so:

session.save_path="192.168.0.200:11211, 192.168.0.1:11211"


Also modify set

session.save_handler = memcache


Overall changed php.ini configuration on Linux machine 1 ( webserver1 ) and Linux machine 2 ( webserver2 ) should be:

session.save_handler = memcache
session.save_path="192.168.0.200:11211, 192.168.0.1:11211"

 

Below is approximately how it should look on both :

webserver1: ~# grep -Ei 'session.save_handler|session.save_path' /etc/php.ini
;; session.save_handler = files
session.save_handler = memcache
;     session.save_path = "N;/path"
;     session.save_path = "N;MODE;/path"
;session.save_path = "/var/lib/php7/sessions"
session.save_path="192.168.0.200:11211, 192.168.0.1:11211"
;       (see session.save_path above), then garbage collection does *not*
 

 

webserver2: ~# grep -Ei 'session.save_handler|session.save_path' /etc/php.ini
;; session.save_handler = files
session.save_handler = memcache
;     session.save_path = "N;/path"
;     session.save_path = "N;MODE;/path"
;session.save_path = "/var/lib/php7/sessions"
session.save_path="192.168.0.200:11211, 192.168.0.1:11211"
;       (see session.save_path above), then garbage collection does *not*


As you can see I have configured memcached on webserver1 to listen on internal local LAN IP 192.168.0.200 and on Local LAN eth iface 192.168.0.1 on TCP port 11211 (this is the default memcached connections listen port), for security or obscurity reasons you might choose another empty one. Make sure to also set the proper firewalling to that port, the best is to enable connections only between 192.168.0.200 and 192.168.0.1 on each of machine 1 and machine 2.

loadbalancing2-php-sessions-scheme-explained
 

5. Enable Memcached for session redundancy


Next step is to configure memcached to allow failover (e.g. use both memcached on 2 linux hosts) and configure session redundancy.
Configure /etc/php/7.3/mods-available/memcache.ini or /etc/php5/mods-available/memcache.ini or respectively to the right location depending on the PHP installed and used webservers version.
 

webserver1 :~#  vim /etc/php/7.3/mods-available/memcache.ini

; configuration for php memcached module
; priority=20
; settings to write sessions to both servers and have fail over
memcache.hash_strategy=consistent
memcache.allow_failover=1
memcache.session_redundancy=3
extension=memcached.so

 

webserver2 :~# vim /etc/php/7.3/mods-available/memcache.ini

; configuration for php memcached module
; priority=20
; settings to write sessions to both servers and have fail over
memcache.hash_strategy=consistent
memcache.allow_failover=1
memcache.session_redundancy=3
extension=memcached.so

 

memcache.session_redundancy directive must be equal to the number of memcached servers + 1 for the session information to be replicated to all the servers. This is due to a bug in PHP.
I have only 2 memcached configured that's why I set it to 3.
 

6. Restart Apache Webservers

Restart on both machines webserver1 and webserver2 Apache to make php load memcached.so
 

webserver1:~# systemctl restart httpd

webserver2:~# systemctl restart httpd

 

7. Restart memcached on machine 1 and 2

 

webserver1 :~# systemctl restart memcached

webserver2 :~# systemctl restart memcached

 

8. Test php sessions are working as expected with a php script

Copy to both website locations to accessible URL a file test_sessions.php:
 

<?php  
session_start();

if(isset($_SESSION[‘georgi’]))
{
echo "Sessions is ".$_SESSION[‘georgi’]."!\n";
}
else
{
echo "Session ID: ".session_id()."\n";
echo "Session Name: ".session_name()."\n";
echo "Setting 'georgi' to 'cool'\n";
$_SESSION[‘georgi’]='cool';
}
?>

 

Now run the test to see PHP sessions are kept persistently:
 

hipo@jeremiah:~/Desktop $ curl -vL -s http://pc-freak.net/session.php 2>&1 | grep 'Set-Cookie:'
< Set-Cookie: PHPSESSID=micir464cplbdfpo36n3qi9hd3; expires=Tue, 10-Nov-2020 12:14:32 GMT; Max-Age=86400; path=/

hipo@jeremiah:~/Desktop $ curl -L –cookie "PHPSESSID=micir464cplbdfpo36n3qi9hd3" http://83.228.93.76/session.php http://213.91.190.233/session.php
Session is cool!
Session is cool!

 

Copy to the locations that is resolving to both DNS servers some sample php script such as sessions_test.php  with below content:

<?php
    header('Content-Type: text/plain');
    session_start();
    if(!isset($_SESSION[‘visit’]))
    {
        echo "This is the first time you're visiting this server\n";
        $_SESSION[‘visit’] = 0;
    }
    else
            echo "Your number of visits: ".$_SESSION[‘visit’] . "\n";

    $_SESSION[‘visit’]++;

    echo "Server IP: ".$_SERVER[‘SERVER_ADDR’] . "\n";
    echo "Client IP: ".$_SERVER[‘REMOTE_ADDR’] . "\n";
    print_r($_COOKIE);
?>

Test in a Web Opera / Firefox / Chrome browser.

You should get an output in the browser similar to:
 

Your number of visits: 15
Server IP: 83.228.93.76
Client IP: 91.92.15.51
Array
(
    [_ga] => GA1.2.651288003.1538922937
    [__utma] => 238407297.651288003.1538922937.1601730730.1601759984.45
    [__utmz] => 238407297.1571087583.28.4.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=(not provided)
    [shellInABox] => 467306938:1110101010
    [fpestid] => EzkIzv_9OWmR9PxhUM8HEKoV3fbOri1iAiHesU7T4Pso4Mbi7Gtt9L1vlChtkli5GVDKtg
    [__gads] => ID=8a1e445d88889784-22302f2c01b9005b:T=1603219663:RT=1603219663:S=ALNI_MZ6L4IIaIBcwaeCk_KNwmL3df3Z2g
    [PHPSESSID] => mgpk1ivhvfc2d0daq08e0p0ec5
)

If you want to test php sessions are working with text browser or from another external script for automation use something as below PHP code:
 

<?php
// save as "session_test.php" inside your webspace  
ini_set('display_errors', 'On');
error_reporting(6143);

session_start();

$sessionSavePath = ini_get('session.save_path');

echo '<br><div style="background:#def;padding:6px">'
   , 'If a session could be started successfully <b>you should'
   , ' not see any Warning(s)</b>, otherwise check the path/folder'
   , ' mentioned in the warning(s) for proper access rights.<hr>';
echo "WebServer IP:" . $_SERVER[‘SERVER_ADDR’] . "\n<br />";
if (empty($sessionSavePath)) {
    echo 'A "<b>session.save_path</b>" is currently',
         ' <b>not</b> set.<br>Normally "<b>';
    if (isset($_ENV[‘TMP’])) {
        echo  $_ENV[‘TMP’], ‘” ($_ENV[“TMP”]) ';
    } else {
        echo '/tmp</b>" or "<b>C:\tmp</b>" (or whatever',
             ' the OS default "TMP" folder is set to)';
    }    
    echo ' is used in this case.';
} else {
    echo 'The current "session.save_path" is "<b>',
         $sessionSavePath, '</b>".';
}

echo '<br>Session file name: "<b>sess_', session_id()
   , '</b>".</div><br>';
?>

You can download the test_php_sessions.php script here.

To test with lynx:

hipo@jeremiah:~/Desktop $ lynx -source 'https://pc-freak.net/test_php_sessions.php'
<br><div style="background:#def;padding:6px">If a session could be started successfully <b>you should not see any Warning(s)</b>, otherwise check the path/folder mentioned in the warning(s) for proper access rights.<hr>WebServer IP:83.228.93.76
<br />The current "session.save_path" is "<b>tcp://192.168.0.200:11211, tcp://192.168.0.1:11211</b>".<br>Session file name: "<b>sess_5h18f809b88isf8vileudgrl40</b>".</div><br>

Find largest files on AIX system root / show biggest files and directories in AIX folder howto

Friday, November 6th, 2020

ibm-aix-logo-find-largest-files-and-directories-on-system-to-free-space-if-disk-is-full

On an AIX server if you get a root directory ( / ) to be completely full problem and the AIX running services are unable to write their pid files and logs for example in /tmp /admin /home /var/tmp /var/log/ and rest of directory structure or the system is almost full with mounted filesystems which shows it is 90% or 95%+ full on main partition,  the system is either already stuck or it is on the way to stop functiononing normally. Hence the only way to recover IBM AIX machine to a normal behavior is to clean up some files (if you can't extend the partition) or add more physical Hard drive, just as we usually do on Linux.

So How can we clean up largest files on AIX?


Lets say we want to find all files on AIX larger than 1 MB.

aix-system:/ $ find / -xdev -size 2048 -ls | sort -r +6
12579 1400 -rw-r—–  1 root      security   1433534 Jun 26  2019 /etc/security/tsd/tsd.dat
 9325 20361 -rw-r—–  1 root      system    20848752 Nov  6 16:02 /etc/security/failedlogin
21862 7105 -rwxr-xr-x  1 root      system     7274915 Aug 24  2017 /sbin/zabbix_agentd
   72 7005 -rw-rw—-  1 root      system     7172962 Nov  6 16:19 /audit/stream.out
24726 2810 -rw——-  1 root      system     2876944 Feb 29  2012 /etc/syslog-ng/core
29314 2391 -r-xr-xr-x  1 root      system     2447454 Jun 25  2019 /lpp/bos/bos.rte.filesystem/7.1.5.32.save/update.16
21844 2391 -r-xr-xr-x  1 root      system     2447414 Jun 25  2019 /sbin/helpers/jfs2/logredo64
21843 2219 -r-xr-xr-x  1 root      system     2271971 Jun 25  2019 /sbin/helpers/jfs2/logredo
29313 2218 -r-xr-xr-x  1 root      system     2270835 Jun 25  2019 /lpp/bos/bos.rte.filesystem/7.1.5.32.save/update.15
22279 1800 -rw-r–r–  1 root      system     1843200 Nov  4 08:03 /root/smit.log
12577 1399 -rw-r–r–  1 root      system     1431685 Jun 26  2019 /etc/security/tsd/.tsd.bk
21837 1325 -r-xr-xr-x  1 root      system     1356340 Jun 25  2019 /sbin/helpers/jfs2/fsck64
29307 1325 -r-xr-xr-x  1 root      system     1356196 Jun 25  2019 /lpp/bos/bos.rte.filesystem/7.1.5.32.save/update.9
   12 1262 -rw——-  1 root      system     1291365 Aug  8  2011 /core

 

Above finds all files greater than 1 MB and sort them in reverse
order with the largest files first.

To search all files larger than 64 Megabytes under root ( / )

aix-system:/ $ find / -xdev -size +131072 -ls | sort -r +6
65139 97019 -rw-r–r–  1 root      system    99347181 Mar 31  2017 /admin/archive.zip


Display 10 largest directories on system

aix-system:/ $ du -a /dir | sort -n -r | head -10


Show biggest files and directories in a directory

 

aix-system:/ $ du -sk * | sort -n
4       Mail
4       liste
4       my_user
4       syslog-ng.conf
140     smit.script
180     smit.transaction
1804    smit.log

Below du display the size of all files and directories in the current directory with the biggest being at the bottom.

 

List all largest files in dir decrasingly. If a directory is matches show all sub-dirs largest files.

aix-system:/ $ ls -A . | while read name; do du -sk $name; done | sort -nr

Below ls + while loop command sorts disk usage for all files in the current directory by size, in decreasing order. If the file we suspect happens to be a directory, we can then change into that directory, and re-run the preceding command to determine what is taking up space within that directory.

Continue these steps until you find the desired file or files, at which point you can take appropriate actions.

If the bottom-most item is a directory, then cd into that directory and run the du command again. Keep drilling down until you find the biggest files on your system and get rid of them to save some space.

Fix Oracle virtualbox Virtual Machine inacessible error in Linux / Windows Host OS

Monday, November 2nd, 2020

Fix Oracle virtualbox Virtual Machine inacessible error in Linux / Windows Host OS

Say you have installed a Virtual Machine on a Host OS be it Windows 7 / 10 or some GNU / Linux / FreeBSD OS and suddenly after a PC shutdown / restart the Virtual machine shows as it couldn't be run by Ora Virtualbox anymore with a message of VM Machine "inaccessible", what is causing this and how to fix it?

Virtualbox-virtual-machine-in-inaccessible-state-screenshot
This error is usually caused by the Guest Operating System's forceful behavior or an OS system crash such as sudden hang due to kernel error or due to sudden electricity drop. Whatever the reason if improper sending of termination process signals to Oracle Vbox are not properly handled this is causing the VBox to not recreate its own files and kill (close) the application of Oracle Virtualbox program in gracious way.

On Windows Virtualization Host OS the common files that needs to be tampered by Virtualbox are found under Virtualbox VMs\Name-of-VM:

virtualbox-vm-inacessible-_error-screenshot.png

For example if you have a Ubuntu installed

Virtualbox-virtual-machine-in-inaccessible-state-screenshot.png
C:\Users\\VirtualBox VMs\Ubuntu

If you have CentOS7 installed instead it will be under

C:\Users\\VirtualBox VMs\CentOS7

Usually under this dir you will find files which are with .vbox extension.

The virtual box files with extension .vbox contain metadata the virtualbox hypervisor requires to resolve the guest virtual OS' configuration.
If the main .vbox file is corrupted (i.e. reporting that it is empty) then use the backup .vbox-prev file to recover the contents of the original file.

How to solve the Virtualbox inacessible weird error:

Usually under the Virtualbox VMs\VM_name you'll find a directory / filestructure like:
 

Logs/
Snapshot/
VM_Name.vbox
VM_Name.vbox-prev
VM_Name.vbox-tmp

 

 

1. Considering .vbox is empty Rename the empty .vbox files a temporary name (e.g. rename VM_Name.vbox to VM_Name-empty.vbox). If you're unsure whether it is empty you can check by opening the file in a text editor and make sure it is empty.

2. Then make a copy of the backup file VM_Name.vbox-prev, where the copy will have the same name as the original but with the word "copy" appended to it (i.e. VM_Name.vbox-prev is renamed to VM_Name_copy.vbox-prev) as well as copy VM_Name.vbox-tmp to VM_Name_copy.vbox-tmp.

! Note that it is important to retain the original backup .vbox-prev file it should not be altered or itself renamed.

3. Now go rename the copy of the newly created .vbox-prev file VM_Name.vbox-prev to the name of the empty .vbox file (VM_Name.vbox).

Now that this is done you may add the .vbox file (guest os) back into the VBOX hypervisor.

If for some reason this did not work and you have a proper working copy of the Virtual Machine under VM_Name.vbox-tmp another approach to try is:
 

1.  Go to your Virtualbox folder i.e. C:\Users\hipo\VirtualBox VMs\Ubuntu

2. Check for file extensions files Ubuntu.vbox-tmp or Ubuntu.vbox-prev needed are there.

3. Overwrite Ubuntu.vbox file with the -tmp one, Just rename file from Ubuntu.vbox-tmp to Ubuntu.vbox

4.  Exit from Virtual Machine and Power it on again.

Hopefully this should recovered the state and snapshot of the "inaccessible" guest VM and
you should now see error gone away and VM will work as before.