[Bug 661654] Re: pam_motd should log the error when run-parts fails

[compdoc]

This problem occurs in 12.04.

Deleting /etc/update-motd.d/20-cpu-checker fixes the problem.

Do I understand correctly that cpu checking will no longer be done?

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https://bugs.launchpad.net/bugs/661654

Title:
  pam_motd should log the error when run-parts fails

Status in “pam” package in Ubuntu:
  Triaged

Bug description:
  Binary package hint: libpam-modules

  ** Problem:
  pam_motd module creates the file /var/run/motd.new but doesn't rename it into /var/run/motd.
  The /etc/motd symlink points to /var/run/motd and at each user login are shown old informations.

  ** Repeatable:
  Yes, always

  ** How to repeat:
  You need to force "run-parts /etc/update-motd.d" to exit with errors.
  To complete this task just add in the update-motd.d chain a script that exits with error or a symlink to a script that doesn't exist.

  
  ** Explanation:
  I discover this issue while upgrading from lucid to maverik (server edition).
  For some reason, the package update-notifier-common was removed and I was full of broken symlinks in the update-motd.d chain.
  At each ssh login I was presented with stale informations.

  Looking into the pam_motd.c code I found the problem.
  The module performs a system("run-parts /etc/update-motd.d > /var/run/motd.new") call, that returns a non-zero value if run-parts exits with errors.
  If the system() call returns a non-zero value, the following rename() call is not executed.
  The file /var/run/motd.new is *always* created and written to disk with the output of the working scripts.
  We are in the situation where the /var/run/motd.new is updated but never renamed into /var/run/motd, if some scripts have bugs or exit with errors.

  I have attached a patch that should solve this problem.
  The rename() call is not blocked by the system() call and moreover if run-parts exits with a non-zero value, pam_syslog is used to log the error and help sysadmins to find rapidly the problem.
  Within the patch, the rename() call is always executed, even if run-parts fails totally and /var/run/motd.new is not created.
  In this case, the rename() call doesn't perform the renaming and returns a non-zero value (but we are not interested in it).

  Thanks,
  Yusef

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