[Bug 1951491] Re: Can't run snaps: .slice/session-1.scope is not a snap cgroup

[Maciej Borzecki]

I've commented before, but if your desktop session is correctly set up,
the systemd --user instance should be available, then a transient scope
can be created for snap and proper device access filtering can be set up
in that cgroup, thus completing the sandbox. Cgroup v1 works
differently, in that there is a separate hierarchy which could be set up
for a snap and there's no need to ask ssytemd to set up anything on
behalf of the snap. This is no longer the case for v2.

AFAICT gdm/kdm/xdm seem to be able to do that correctly. Most trouble
seems to be coming from X2go/vnc or similar solutions which appear to
give you a desktop access, but it's half baked, and are either missing
session dbus or the systemd --user instance. Perhaps it's not really
going through PAM, hence things that would have been set up through
pam_systemd are missing.

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Title:
  Can't run snaps: .slice/session-1.scope is not a snap cgroup

Status in snapd package in Ubuntu:
  Invalid
Status in systemd package in Ubuntu:
  Confirmed
Status in snapd package in Debian:
  New

Bug description:
  I just upgraded from hirsute to impish using do-release-upgrade. On
  the upgraded system, I can't run either firefox or chromium (both of
  which worked fine under hirsute). Both fail with:

  /user.slice/user-NNN.slice/session-1.scope is not a snap cgroup where
  NNN is my uid

  With firefox, I was able to fix the problem with:

  snap remove --purge firefox
  apt purge firefox
  apt install firefox

  Now firefox works. But I tried the same thing substituting chromium-
  browser for firefox, and it didn't help: chromium fails with the same
  error message.

  I guess there must be something left over from the hirsute version of
  snapd that isn't getting noticed or cleared by the impish version?

  Someone suggested this might be related to bug 1850667, but that bug
  is marked fixed as of a couple months ago, and I just did this upgrade
  today. Also, it doesn't mention the error message I'm seeing.

  ProblemType: Bug
  DistroRelease: Ubuntu 21.10
  Package: snapd 2.53+21.10ubuntu1
  ProcVersionSignature: Ubuntu 5.13.0-21.21-generic 5.13.18
  Uname: Linux 5.13.0-21-generic x86_64
  ApportVersion: 2.20.11-0ubuntu71
  Architecture: amd64
  CasperMD5CheckResult: unknown
  Date: Thu Nov 18 18:12:45 2021
  InstallationDate: Installed on 2020-04-29 (568 days ago)
  InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
  SourcePackage: snapd
  UpgradeStatus: Upgraded to impish on 2021-11-18 (0 days ago)

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