Actualització del missatge del dia (MOTD)

When logging into an Ubuntu server you may have noticed the informative Message Of The Day (MOTD). This information is obtained and displayed using a couple of packages:

  • landscape-common: provides the core libraries of landscape-client, which can be used to manage systems using the web based Landscape application. The package includes the /usr/bin/landscape-sysinfo utility which is used to gather the information displayed in the MOTD.

  • update-motd: is used to automatically update the MOTD via cron.

The update-motd utility has several options to further customize the MOTD:

  • --disable: prevents automatic updates of the MOTD. Using this option creates the /var/lib/update-motd/disabled file, which if present stops update-motd from modifying /etc/motd.

  • --enable: enables the automatic MOTD updates. If /var/lib/update-motd is present it will be removed.

  • --force: does a one time update of /etc/motd, overriding update-motd if it has been disabled.

  • d, hourly, weekly, monthly: option will run the scripts in /etc/update-motd.d/ (default), /etc/update-motd.d/hourly, /etc/update-motd.d/weekly, or /etc/update-motd.d/monthly respectively.

update-motd executes the scripts in /etc/update-motd.d in order based on the number prepended to the script. Separate cron scripts execute every ten minutes, hourly, weekly, and monthly running the corresponding scripts in /etc/update-motd.d. The output of the scripts is written to /var/run/update-motd/, keeping the numerical order, then concatenated with /etc/motd.tail and written to /etc/motd.

You can add your own dynamic information to the MOTD. For example, to add local weather information:

  • First, install the weather-util package:

    sudo apt-get install weather-util
    
  • The weather utility uses METAR data from the National Oceanic and Atmospheric Administration and forecasts from the National Weather Service. In order to find local information you will need the 4-character ICAO location indicator. This can be determined by browsing to the National Weather Service site.

    Although the National Weather Service is a United States government agency there are weather stations available world wide. However, local weather information for all locations outside the U.S. may not be available.

  • Create /usr/local/bin/local-weather, a simple shell script to use weather with your local ICAO indicator:

    #!/bin/sh
    ##########################################################################
    #
    # Prints the local weather to /var/run/update-motd/60-local-weather  
    # for update-motd.
    #
    ##########################################################################
    
    # Replace KINT with your local weather station.
    # Local stations can be found here: http://www.weather.gov/tg/siteloc.shtml
    
    echo "" > /var/run/update-motd/60-local-weather
    weather -i KINT >> /var/run/update-motd/60-local-weather
    
    
  • Make the script executable:

    sudo chmod 755 /usr/local/bin/local-weather
    
  • Next, create a symlink to /etc/update-motd.d/60-local-weather:

    sudo ln -s /usr/local/bin/local-weather /etc/update-motd.d/60-local-weather
    
  • Finally, update the MOTD:

    sudo update-motd
    

You should now be greeted with some useful information, and some information about the local weather that may not be quite so useful. Hopefully the local-weather example demonstrates the flexibility of update-motd.