Monday, July 19, 2021

Ubuntu logon info and message of the day (motd)

This post will show you how to determine your public-facing IP address from the command line.

Upon an interactive logon, Ubuntu prints some brief machine information. This includes a header, sysinfo from /usr/bin/landscape-sysinfo and a summary of available patches.

You may add your own scripts by creating a bash script in /etc/update-motd.d and set the execute permission on the file. The files in the directory have a particular naming convention, and are run in alphabetical (numeric) order.

On external facing machines, I often create a script which will print the external IP address following the networking info of the landscape-sysinfo script.

Create file /etc/update-motd.d/61-external-ip owned by root
and give it execute permission:
sudo chmod 755 /etc/update-motd.d/61-external-ip


Place the following in this new file:

ONE=$(/usr/bin/curl -s
TWO=$(/usr/bin/curl -s

if [ $ONE = $TWO ]
    printf "  External IPv4: "
    printf $ONE
    printf "  External IPv4 may be: "
    printf $ONE
    printf " or"
    printf $TWO
printf "\n"

Save the file, then logon to the machine and look at the interactive logon messages. Some of the output will look like:

Welcome to Ubuntu 20.04.2 LTS (GNU/Linux 5.4.0-77-generic x86_64)

  System information as of Mon 19 Jul 2021 01:30:42 PM MDT

  System load:              0.58
  Usage of /:               5.4% of 1.79TB
  Memory usage:             15%
  Swap usage:               0%
  Temperature:              44.0 C
  Processes:                173
  Users logged in:          1
  IPv4 address for enp0s25:
  External IPv4: 123.456.7.89

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