canonical-ubuntu-qa team mailing list archive

[Paride Legovini <2103695@xxxxxxxxxxxxxxxxxx>]

I'd like to add something of this one, for future reference. It is easy
to reproduce the issue on an Ubuntu system (your laptop), taking
autopkgtest out of the equation. I'll outline steps to reproduce here
below. I'll assume passwordless sudo and passwordless ssh for
$USER@localhost.

### "sudo su" from a terminal ###

This akin to using autopkgtest-virt-qemu, which connect to the VM via a
serial console. From a terminal (gnome termina, tilix, ...), run

$ env | grep XDG_RUNTIME
XDG_RUNTIME_DIR=/run/user/1000

$ sudo env | grep XDG_RUNTIME
[no output]

$ sudo su paride -c env | grep XDG_RUNTIME
XDG_RUNTIME_DIR=/run/user/1000

See how the first "sudo" cleans the XDG_ variables, but then su
reattaches to the user session, and the XDG variables are back.

### "sudo su" via ssh ###

We do the same as above, but via ssh:

$ ssh localhost -- env | grep XDG_RUNTIME
XDG_RUNTIME_DIR=/run/user/1000

$ ssh localhost -- sudo env | grep XDG_RUNTIME
[no output]

$ ssh localhost -- sudo su paride -c env | grep XDG_RUNTIME
[no output]

Note the no output in the latest command, and how that's different in
the terminal session. This is the root of the problem.

### end ###

On why that happens, there are a bunch of useful pointers here:

https://unix.stackexchange.com/questions/346841/why-does-sudo-i-not-set-
xdg-runtime-dir-for-the-target-user

Looks like a way to get the user session back when using the
ssh->sudo->su path is using machinectl, but we can't replace su with
machinectl in autopkgtest. But perhaps machinectl can be used within the
existing test to get the user session from within the test script.

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https://bugs.launchpad.net/bugs/2103695

Title:
  autopkgtest runner does not run a systemd user instance

Status in Auto Package Testing:
  Won't Fix

Bug description:
  Both autopkgtest-virt-lxd and autopkgtest-virt-qemu, as well as
  debian's infra autopkgtest runners, have a systemd user session
  instance running during the test; this is evidenced by the fact that
  `$XDG_RUNTIME_DIR` is set, and you can talk to it with `systemctl
  --user` commands.

  Ubuntu's infrastructure instead does not have a systemd user instance
  running, creating a divergence in the test environment.

  Here's the most minimal reproducer:

     dget https://launchpad.net/~aleasto/+archive/ubuntu/tests/+sourcefiles/empty/1.0/empty_1.0.dsc
     autopkgtest ./empty_1.0.dsc -- qemu autopkgtest-plucky-amd64.img

  where autopkgtest-plucky-amd64.img is generated by autopkgtest-
  buildvm-ubuntu-cloud.

  The test runs the following script:

     echo "XDG_RUNTIME_DIR=$XDG_RUNTIME_DIR"
     systemctl --user status

  The test passes locally, but not on ubuntu's infrastructure. Here's a log from my ppa:
  https://autopkgtest.ubuntu.com/results/autopkgtest-plucky-aleasto-tests/plucky/amd64/e/empty/20250319_161854_94e24@/log.gz

  Expected result:

  autopkgtest [10:03:00]: test test-systemd-user: [-----------------------
  XDG_RUNTIME_DIR=/run/user/1000
  ● autopkgtest
      State: running
      Units: 133 loaded (incl. loaded aliases)
       Jobs: 0 queued
     Failed: 0 units
      Since: Thu 2025-03-20 10:03:01 CET; 136ms ago
    systemd: 257.4-1ubuntu1
    Tainted: unmerged-bin
     CGroup: /user.slice/user-1000.slice/user@1000.service
             └─init.scope
               ├─15648 /usr/lib/systemd/systemd --user
               └─15650 "(sd-pam)"

  Actual result:

  autopkgtest [16:18:34]: test test-systemd-user: [-----------------------
  XDG_RUNTIME_DIR=
  Failed to connect to user scope bus via local transport: $DBUS_SESSION_BUS_ADDRESS and $XDG_RUNTIME_DIR not defined (consider using --machine=<user>@.host --user to connect to bus of other user)

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