gdm3 will not unlock session (or switch to a PTY) when out of inotify watches ["No space left on device"]

[Dan Watkins]

The log messages from around the time when I attempt an unlock look like this:

Oct 24 13:38:13 surprise gdm-password]: AccountsService: Failed to monitor logind session changes: No space left on device
Oct 24 13:38:31 surprise gdm-password]: message repeated 2 times: [ AccountsService: Failed to monitor logind session changes: No space left on device]
Oct 24 13:38:32 surprise gsd-rfkill[1564]: g_object_notify: object class 'CcRfkillGlib' has no property named 'kernel-noinput'
Oct 24 13:38:32 surprise kernel: [16851.666217] rfkill: input handler enabled
Oct 24 13:38:40 surprise gnome-shell[937]: JS WARNING: [resource:///org/gnome/shell/gdm/realmd.js 130]: reference to undefined property "_loginFormat"
Oct 24 13:38:40 surprise gnome-shell[937]: JS WARNING: [resource:///org/gnome/shell/gdm/realmd.js 142]: reference to undefined property "_loginFormat"
Oct 24 13:38:48 surprise gdm-password]: AccountsService: Failed to monitor logind session changes: No space left on device

I run CrashPlan for backups, and https://bugzilla.redhat.com/show_bug.cgi?id=1081004 suggests that these messages are happening because I've run out of inotify watches on my system.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: gdm3 3.26.1-3ubuntu3
ProcVersionSignature: Ubuntu 4.13.0-16.19-generic 4.13.4
Uname: Linux 4.13.0-16-generic x86_64
ApportVersion: 2.20.7-0ubuntu3
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Tue Oct 24 13:47:25 2017
InstallationDate: Installed on 2017-10-23 (0 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20171018)
SourcePackage: gdm3
UpgradeStatus: No upgrade log present (probably fresh install)

[Dan Watkins (oddbloke)]

This can be worked around by following the instructions at https://support.code42.com/CrashPlan/4/Troubleshooting/Linux_real-time_file_watching_errors, but it seems to me that GDM should handle this gracefully somehow.

[Dan Watkins (oddbloke)]

(It's also worth noting that I couldn't get to a PTY at all, so I had to restart my machine to be able to fix this.)

[Launchpad Janitor (janitor)]

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

[Daniel van Vugt (vanvugt)]

Dan,

I agree in an ideal world all software, at least core software like gdm3, should handle such errors more gracefully and keep working. However finding the time and expertise to make that a reality means it's probably not realistic any time soon.

A more realistic fix is to find what's using up all the resources (if not disk space) and fix/remove that. Please confirm for us if removing/disabling "crashplan" does also workaround the problem, or if the trigger lays in some other software package.

[Dan Watkins (oddbloke)]

As I mentioned in comment #2, this can be worked around. The issue is that GDM3 assumes that it can get an inotify watch and degrades ungracefully when it can't.

[Daniel van Vugt (vanvugt)]

Great. Please send that information upstream to the GDM developers here:

  https://bugzilla.gnome.org/enter_bug.cgi?product=gdm

And when done please tell us the bug ID you created.

[Daniel van Vugt (vanvugt)]

Thank you for reporting this bug to Ubuntu.
Ubuntu 17.10 (artful) reached end-of-life on July 19, 2018.

See this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We appreciate that this bug may be old and you might not be interested in discussing it any more. But if you are then please upgrade to the latest Ubuntu version and re-test. If you then find the bug is still present in the newer Ubuntu version, please add a comment here telling us which new version it is in and change the bug status to Confirmed.