pam_systemd delays SSH login - required?

Question

On our Saucy servers (13.10) we are seeing long delays when logging into the systems via SSH. I figured out it is related to the line

session optional        pam_systemd.so

in /etc/pam.d/common-session.

When I comment that line, login is immediate.

The /var/log/auth.log output that accompanies any delayed login attempts looks like this:

May 21 17:33:58 control02 sshd[18488]: Accepted publickey for daniel.schneller from 10.102.2.9 port 35763 ssh2
May 21 17:33:58 control02 sshd[18488]: pam_unix(sshd:session): session opened for user daniel.schneller by (uid=0)
May 21 17:34:23 control02 sshd[18488]: pam_systemd(sshd:session): Failed to create session: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.

I could not find any definite documentation yet whether or not I need the module at all. I could, of course, leave it commented out, because it seems to only wait for a timeout anyway at the moment, but I would rather understand the underlying cause and fix that, if at all possible, to prevent problems down the road.

Solution

I had the same problem with Debian Jessie 8 and found another solution here: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=770135#46

The command systemctl restart systemd-logind.service or a complete reboot fixed the ssh login delay for me.

Comments

[Michael Miller]

The libpam-systemd package is installed by default on desktop systems but I think not on server installs. Is this a desktop or server install? Are the dbus and systemd-logind upstart jobs running? Does the SSH login get a valid logind session? The timeout seems like a dbus timeout communicating with logind.