[Bug 1855092] Re: [SRU] Please set MOTD_SHOWN=pam when MOTD was shown

[Balint Reczey]

root at ee-motd-verify:~# login ubuntu
Password: 
Welcome to Ubuntu 19.10 (GNU/Linux 5.0.0-37-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

  System information as of Mon Dec 16 14:37:28 UTC 2019

  System load:    0.7       Processes:           28
  Usage of /home: unknown   Users logged in:     0
  Memory usage:   0%        IP address for eth0: 10.84.73.58
  Swap usage:     38%


0 updates can be installed immediately.
0 of these updates are security updates.


The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

To run a command as administrator (user "root"), use "sudo <command>".
See "man sudo_root" for details.

ubuntu at ee-motd-verify:~$ echo $MOTD_SHOWN 
pam
ubuntu at ee-motd-verify:~$ dpkg -l libpam-modules | cat
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                 Version                Architecture Description
+++-====================-======================-============-========================================
ii  libpam-modules:amd64 1.3.1-5ubuntu1.19.10.0 amd64        Pluggable Authentication Modules for PAM


** Tags removed: verification-needed verification-needed-eoan
** Tags added: verification-done verification-done-eoan

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https://bugs.launchpad.net/bugs/1855092

Title:
  [SRU] Please set MOTD_SHOWN=pam when MOTD was shown

Status in pam package in Ubuntu:
  Fix Released
Status in pam source package in Eoan:
  Fix Committed

Bug description:
  [Impact]

    * Users of containers may never see the MOTD of the container if they are always to the container's shell without PAM being involved.
    * MOTD contains important information about the system's health including the security updates to be installed thus it is desired to show MOTD in container shells, too.
    * The fix in update-motd is creating a snippet in /etc/profile.d which shows MOTD, but only if UPDATE_MOTD is not set, to avoid printing MOTD twice.

  [Test Case]

   * Log in to the system, where PAM prints the MOTD.
   * After seeing the MOTD observe MOTD_SHOWN set:
     $ echo $MOTD_SHOWN
     pam
     $

  [Regression Potential]

   * The fix is simple thus it is unlikely to see any regression due to bad implementation.
   * The newly set environment variable may interact with existing software, but this variable seems to be not used:
   https://codesearch.debian.net/search?q=MOTD_SHOWN&literal=1

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