DokuWiki » Infrastructure » Operating System » CentOS 6

h1. Message of the day: Banner-Message

h2. Preliminary note motd

You may find additional useful information at

* http://wiki.centos.org/TipsAndTricks/BannerFiles

h2. Setup motd

The @/etc/motd@ is a file on Unix-like systems that contains a "message of the day".

This file is just static text, therefore we recreate this file every 10 mins with updated information.

I want to say first that this is not the only way of setting up such a system. There are many ways of achieving this goal but this is the way I take.

h3. add script

<pre><code class="bash">

vim /usr/local/bin/gen_motd.sh

</code></pre>

basic example:

<pre>

#!/bin/bash

# JKE 2011-05-14

# create /etc/motd

# to be called by /etc/cron.d/gen_motd

#

echo -e "

*******************************************************************

* xxyyy Janus Server                                            *

*

======h1.                                            *

*                                                               *

* This system is for the use of authorized users only. Usage of *

* this system will be monitored and recorded by system personnel. *

*                                                               *

* Anyone using this system expressly consents to such monitoring*

* and is advised that if such monitoring reveals possible       *

* evidence of criminal activity, system personel may provide the*

* evidence from such monitoring to law enforcement officials.   *

*                                                               *

*******************************************************************

* Version   = `cat /etc/centos-release`

* Kernel    = `uname -r`

* Uptime    = `uptime | sed 's/.*up \([^,]*\), .*/\1/'`

* Mem /free = `cat /proc/meminfo | grep MemTotal | awk {'print $2'}` kB / `cat /proc/meminfo | grep MemFree | awk {'print $2'}` kB 

* Swap/free = `cat /proc/meminfo | grep SwapTotal | awk {'print $2'}` kB / `cat /proc/meminfo | grep SwapFree | awk {'print $2'}` kB

* last updt = `date`

*******************************************************************

" > /etc/motd

</pre>

set shell-script being executeable

<pre><code class="bash">

chmod +x /usr/local/bin/gen_motd.sh

</code></pre>

h3. add script to cron

<pre><code class="bash">

vim /etc/cron.d/gen_motd

</code></pre>

basic example:

<pre>

# JKE 2011-05-14

#

#	min			hr	dom	month	dow	user	command

#	-			-	-	-	-

#	|			|	|	|	|

#	|			|	|	|	+-day of week (0-7) sunday=0 or 7

#	|			|	|	+---------month (1-12)

#	|			|	+-----------------day of month (1-31)

#	|			+-------------------------hour (0-23)

#	+-------------------------------------------------min (0-59)

# 

	5,15,25,35,45,55	*	*	*	*	root	/usr/local/bin/gen_motd.sh

</pre>

h2. Test

* recreate @motd@ manually

* login and check the output (you should see the motd)

<pre><code class="bash">

/usr/local/bin/gen_motd.sh

ssh root@localhost

exit

</code></pre>

* wait minimum 10 mins

* login once more, you should have an updated output