update-motd(5) [linux man page]

update-motd(5)							File Formats Manual						    update-motd(5)

NAME

       update-motd - dynamic MOTD generation

SYNOPSIS

       /etc/update-motd.d/*

DESCRIPTION

       UNIX/Linux  system  adminstrators  often  communicate  important  information  to  console and remote users by maintaining text in the file
       /etc/motd, which is displayed by the pam_motd(8) module on interactive shell logins.

       Traditionally, this file is static text, typically installed by the distribution and only updated on release upgrades,  or  overwritten	by
       the local administrator with pertinent information.

       Ubuntu introduced the update-motd framework, by which the motd(5) is dynamically assembled from a collection of scripts at login.

       Executable scripts in /etc/update-motd.d/* are executed by pam_motd(8) as the root user at each login, and this information is concatenated
       in /var/run/motd.  The order of script execution is determined by the run-parts(8) --lsbsysinit option (basically alphabetical order,  with
       a few caveats).

       On Ubuntu systems, /etc/motd is typically a symbolic link to /var/run/motd.

BEST PRACTICES

       MOTD fragments must be scripts in /etc/update-motd.d, must be executable, and must emit information on standard out.

       Scripts	should be named named NN-xxxxxx where NN is a two digit number indicating their position in the MOTD, and xxxxxx is an appropriate
       name for the script.

       Scripts must not have filename extensions, per run-parts(8) --lsbsysinit instructions.

       Packages should add scripts directly into /etc/update-motd.d, rather than symlinks to other scripts, such that administrators can modify or
       remove  these  scripts  and  upgrades  will not wipe the local changes.	Consider using a simple shell script that simply calls exec on the
       external utility.

       Long running operations (such as network calls) or resource intensive scripts should cache output, and only update that	output	if  it	is
       deemed expired.	For instance:

	 /etc/update-motd.d/50-news
	 #!/bin/sh
	 out=/var/run/foo
	 script="w3m -dump http://news.google.com/"
	 if [ -f "$out" ]; then
	   # Output exists, print it
	   echo
	   cat "$out"
	   # See if it's expired, and background update
	   lastrun=$(stat -c %Y "$out") || lastrun=0
	   expiration=$(expr $lastrun + 86400)
	   if [ $(date +%s) -ge $expiration ]; then
	     $script > "$out" &
	   fi
	 else
	   # No cache at all, so update in the background
	   $script > "$out" &
	 fi

       Scripts should emit a blank line before output, and end with a newline character.  For instance:

	 /etc/update-motd/05-lsb-release
	 #!/bin/sh
	 echo
	 lsb-release -a

FILES

       /etc/motd, /var/run/motd, /etc/update-motd.d

SEE ALSO

       motd(5), pam_motd(8), run-parts(8)

AUTHOR

       This  manpage  and the update-motd framework was written by Dustin Kirkland <kirkland@canonical.com> for Ubuntu systems (but may be used by
       others).  Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License,  Version
       3 published by the Free Software Foundation.

       On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL.

update-motd							   13 April 2010						    update-motd(5)