man > update-motd(5)

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 up‐
       dated on release upgrades, or overwritten by the local administrator with pertinent  informa‐
       tion.

       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 /run/motd.dynamic.  The order of script
       execution is determined by the run-parts(8) --lsbsysinit option (basically  alphabetical  or‐
       der, with a few caveats).

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


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

       Scripts should be named named NN-xxxxxx where NN is a two digit number indicating their posi‐
       tion 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=/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 in‐
       stance:

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


FILES
       /etc/motd, /run/motd.dynamic, /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@canoni‐
       cal.com> for Ubuntu systems (but may be used by others).  Permission is granted to copy, dis‐
       tribute and/or modify this document under the terms of the GNU General Public  License,  Ver‐
       sion 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)