[Bug 1944711] Re: restarting systemd-logind loses all existing sessions

[Lukas Märdian]

Thank you Michael for the verification. I can confirm this is working as
expected as of systemd 245.4-4ubuntu3.14 from (focal-proposed)

slyon at ff:~$ dpkg -l | grep systemd
[...]
ii  systemd                        245.4-4ubuntu3.14                     amd64
slyon at ff:~$ loginctl list-sessions
SESSION  UID USER  SEAT TTY  
     c2 1001 slyon      pts/1

1 sessions listed.

root at ff:~# systemctl restart systemd-logind

slyon at ff:~$ loginctl list-sessions
SESSION  UID USER  SEAT TTY  
     c2 1001 slyon      pts/1

1 sessions listed.

The networking after resume issue indeed seems to be unrelated.

** Tags removed: verification-needed-focal
** Tags added: verification-done-focal

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Title:
  restarting systemd-logind loses all existing sessions

Status in systemd package in Ubuntu:
  Fix Released
Status in systemd source package in Focal:
  Fix Committed

Bug description:
  [impact]

  restarting the systemd-logind service loses all existing sessions

  [test case]

  ubuntu at test-f:~$ loginctl list-sessions
  SESSION  UID USER   SEAT TTY
     3789 1000 ubuntu      pts/0

  1 sessions listed.
  ubuntu at test-f:~$ journalctl -b -u systemd-logind
  -- Logs begin at Thu 2021-09-23 11:11:57 UTC, end at Thu 2021-09-23 11:22:55 UTC. --
  Sep 23 11:22:51 test-f systemd[1]: Starting Login Service...
  Sep 23 11:22:51 test-f systemd-logind[198]: New seat seat0.
  Sep 23 11:22:51 test-f systemd[1]: Started Login Service.
  Sep 23 11:22:52 test-f systemd-logind[198]: New session 3789 of user ubuntu.
  ubuntu at test-f:~$ sudo systemctl restart systemd-logind
  ubuntu at test-f:~$ journalctl -b -u systemd-logind
  -- Logs begin at Thu 2021-09-23 11:11:57 UTC, end at Thu 2021-09-23 11:23:07 UTC. --
  Sep 23 11:22:51 test-f systemd[1]: Starting Login Service...
  Sep 23 11:22:51 test-f systemd-logind[198]: New seat seat0.
  Sep 23 11:22:51 test-f systemd[1]: Started Login Service.
  Sep 23 11:22:52 test-f systemd-logind[198]: New session 3789 of user ubuntu.
  Sep 23 11:23:07 test-f systemd[1]: Stopping Login Service...
  Sep 23 11:23:07 test-f systemd[1]: systemd-logind.service: Succeeded.
  Sep 23 11:23:07 test-f systemd[1]: Stopped Login Service.
  Sep 23 11:23:07 test-f systemd[1]: Starting Login Service...
  Sep 23 11:23:07 test-f systemd-logind[469]: Failed to add user by file name 1000, ignoring: Invalid argument
  Sep 23 11:23:07 test-f systemd-logind[469]: User enumeration failed: Invalid argument
  Sep 23 11:23:07 test-f systemd-logind[469]: User of session 3789 not known.
  Sep 23 11:23:07 test-f systemd-logind[469]: Session enumeration failed: No such file or directory
  Sep 23 11:23:07 test-f systemd-logind[469]: New seat seat0.
  Sep 23 11:23:07 test-f systemd[1]: Started Login Service.
  ubuntu at test-f:~$ loginctl list-sessions
  No sessions.

  [regression potential]

  any regression would likely occur during a systemd-logind restart,
  likely causing a loss of current login sessions.

  [scope]

  this is needed only in f

  this is fixed upstream by commit
  ac4e03d45bcf4ad2e570cabdb218e9bac003cc80 which is included in v246, so
  this is fixed in h and later already.

  in b, the function used to parse the /run/systemd/users/* files allows
  either usernames or uids, so this bug does not exist there

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