[Bug 1803601] Re: motd-news.service scheduled even when /etc/update-motd.d/50-motd-news is not executable

[Tired Sysadmin]

Simon Déziel (sdeziel) wrote:
> IIRC, `chmod -x` snippets from /etc/update-motd.d/ was the way to go a
> few releases ago when it was consumed by run-parts.

In 22.04 it's still handled by run-parts, and the man page documents it
as such.  Specifically by

$ strings /lib/x86_64-linux-gnu/security/pam_motd.so | grep run-parts
/usr/bin/env -i PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin run-parts --lsbsysinit /etc/update-motd.d > /run/motd.dynamic.new

in its primary use case.  The "fetch new ads on boot" motd-news.service
for this bug report runs one of the scripts directly, but the directory
is still a run-parts input.

We could disable scripts by renaming them to something that won't be
found by the '--lsbsysinit' file patterns, but that would only solve the
problem for "at login" updates, not the "at boot" updates through
systemd.


> It's merely to avoid harmless surprise and keep the old sysadmins happy,

Service errors is hardly a "surprise", and you don't need to be
condescending about it.


wontfix (wontfix) wrote:
> and that is to set ENABLED=0 in /etc/default/motd-news."
> 
> This file no longer exists by default in Ubuntu 22.04 Jammy.

$ grep VERSION /etc/os-release
VERSION_ID="22.04"
VERSION="22.04 LTS (Jammy Jellyfish)"
VERSION_CODENAME=jammy
$ dpkg -S /etc/default/motd-news
motd-news-config: /etc/default/motd-news
$ apt show motd-news-config
Package: motd-news-config
Priority: optional
Source: base-files
Task: cloud-image, ubuntu-wsl, server, ubuntu-server-raspi
APT-Manual-Installed: no
[several header elided]

It certainly existed by default from the beginning of the server
installation I'm working with.  However, it's "priority: optional" so
perhaps that's what you mean by "not default"; it likely wouldn't be
there for a standard desktop installation.

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https://bugs.launchpad.net/bugs/1803601

Title:
  motd-news.service scheduled even when /etc/update-motd.d/50-motd-news
  is not executable

Status in base-files package in Ubuntu:
  Triaged

Bug description:
  update-motd(5) says:

   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  execu‐
   tion is determined by the run-parts(8) --lsbsysinit option (basically alphabetical order, with
   a few caveats).

  So sysadmins are used to "chmod -x" motd fragments from /etc/update-
  motd.d/ to prevent their execution. When doing so for /etc/update-
  motd.d/50-motd-news, I noticed that motd-news.timer was still trying
  to execute the motd-news.service unit which then logged a failure:

   systemd[3704]: motd-news.service: Failed to execute command: Permission denied
   systemd[3704]: motd-news.service: Failed at step EXEC spawning /etc/update-motd.d/50-motd-news:
    Permission denied
   systemd[1]: motd-news.service: Main process exited, code=exited, status=203/EXEC
   systemd[1]: motd-news.service: Failed with result 'exit-code'.
   systemd[1]: Failed to start Message of the Day.

  
  The motd-news.service unit looks like this:

  $ systemctl cat motd-news.service
  # /lib/systemd/system/motd-news.service
  [Unit]
  Description=Message of the Day
  After=network-online.target
  Documentation=man:update-motd(8)

  [Service]
  Type=oneshot
  ExecStart=/etc/update-motd.d/50-motd-news --force

  
  This problem was observed on a Bionic system:

  $ lsb_release -rd
  Description:	Ubuntu 18.04.1 LTS
  Release:	18.04
  $ apt-cache policy base-files
  base-files:
    Installed: 10.1ubuntu2.3
    Candidate: 10.1ubuntu2.3
    Version table:
   *** 10.1ubuntu2.3 500
          500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
          100 /var/lib/dpkg/status
       10.1ubuntu2.2 500
          500 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
       10.1ubuntu2 500
          500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages

  But the problem also exist in Disco.

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