Comment 1 for bug 1453861

We could reproduce the problem on a machine that was mothballed after installing 14.04 on March 12, 2015.

1) The machine still booted fine.
Linux 3.13.0-48-generic #80-Ubuntu SMP Thu Mar 12 11:16:15 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

2) We updated the machine with all patches released between March 12 and today.

3) The machine still booted fine.
Linux 3.13.0-52-generic #86-Ubuntu SMP Mon May 4 04:32:59 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

4) We switched from NIS to LDAP authentication. (We had implemented that sometime after the machine was mothballed.)

5) LDAP works fine.

6) Machine HANGS at reboot, just like the other affected machines.

The conclusion would be that upstart gets stuck at boot because of something related to the switch to LDAP.
The changes were:

a) installed packages
libnss-ldap:amd64 (264-2.2ubuntu4.14.04.1),
auth-client-config:amd64 (0.9ubuntu1, automatic),
ldap-auth-config:amd64 (0.5.3, automatic),
libpam-ldap:amd64 (184-8.5ubuntu3),
ldap-auth-client:amd64 (0.5.3, automatic)

b) edited files:
/etc/ldap.conf
/etc/ldap/ldap.conf
/etc/nsswitch.conf (added lines "passwd_compat: ldap", "group_compat: ldap". "shadow_compat: ldap")

In order to confirm this, we booted from CD and commented out the lines added to /etc/nsswitch.conf, to make the machine use NIS instead of LDAP again. The machine booted without any problem.

At this stage, our guess is that some upstart script forces a lookup of a user ID before the network is up, such that the LDAP server can't be reached, and the init process gets stuck. For some reason, with NIS this gets handled better.

Looking for a UID problem in the log files, there was only this (from a successful boot with NIS, because no logs are written when LDAP is used and the boot fails). I have no clue whether that is anyhow related to the issue.

May 12 13:27:38 machine_name NetworkManager[1195]: <warn> error requesting auth for org.freedesktop.NetworkManager.wifi.share.protected: (3) GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner: GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner: Could not get UID of name ':1.20': no such name
May 12 13:27:38 machine_name NetworkManager[1195]: <warn> error requesting auth for org.freedesktop.NetworkManager.wifi.share.open: (3) GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner: GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner: Could not get UID of name ':1.20': no such name