/etc/pam.d/login runs /etc/update-motd.d scripts twice

[Jamie Strandboge]

In performing install audits I noticed the following change to /etc/pam.d/login:
+ session optional pam_motd.so motd=/run/motd.dynamic
  session optional pam_motd.so

Per man (8) pam_motd, this means that the scripts in /etc/update-motd.d are run twice. One of these should use 'noupdate', like in /etc/pam.d/sshd:
# Print the message of the day upon successful login.
# This includes a dynamically generated part from /run/motd.dynamic
# and a static (admin-editable) part from /etc/motd.
session optional pam_motd.so motd=/run/motd.dynamic noupdate
session optional pam_motd.so # [1]

(It seems slightly odd to me that sshd will update /etc/motd dynamically rather than /run/motd.dynamic, but that is not this bug)

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: login 1:4.1.5.1-1ubuntu3
ProcVersionSignature: Ubuntu 3.8.0-17.27+dbusdev1-generic 3.8.6
Uname: Linux 3.8.0-17-generic x86_64
ApportVersion: 2.9.2-0ubuntu5
Architecture: amd64
Date: Tue Apr 16 08:07:11 2013
InstallationDate: Installed on 2011-06-28 (657 days ago)
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110425.2)
MarkForUpload: True
SourcePackage: shadow
UpgradeStatus: Upgraded to raring on 2013-02-14 (61 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Colin Watson (cjwatson)]

Re sshd: pam_motd (without noupdate) actually updates /var/run/motd, not /etc/motd. This is explained in pam_motd's source:

    /* Run the update-motd dynamic motd scripts, outputting to /var/run/motd.
       If /etc/motd -> /var/run/motd, the displayed MOTD will be dynamic.
       Otherwise, the admin can force a static MOTD by breaking that symlink
       and publishing into an /etc/motd text file. */

It's a bit weird, but I didn't write it. :-)

[Launchpad Janitor (janitor)]

This bug was fixed in the package shadow - 1:4.1.5.1-1ubuntu4

---------------
shadow (1:4.1.5.1-1ubuntu4) raring; urgency=low

  * Pass noupdate to pam_motd call for /run/motd.dynamic, to avoid running
    /etc/update-motd.d/* scripts twice (LP: #1169558).
 -- Colin Watson <email address hidden> Thu, 18 Apr 2013 01:01:45 +0100