Bug#813789: systemd: su -l does not start/attach to user session

[Boris Kolpackov]

Package: systemd
Version: 215-17+deb8u2
Severity: normal

Hi,

I keep seeing in various places (Debian-related and otherwise) that
su does not start a new systemd user session because it is not a
proper login. The symptom is:

# su -l boris
$ systemctl --user status
Failed to get D-Bus connection: Connection refused

To me, it seems su -/-l/--login is just like login (what is the
conceptual difference between su -l boris and ssh boris at 127.0.0.1?).
It also does not attach to a (lingering) user session, unless I
manually do:

export XDG_RUNTIME_DIR=/run/user/`id -u`

[Note that in this case XDG_SESSION_ID will still be bogus but
apparently it is harmless since it is for information purposes
only.]

It seems the decision whether it is a proper login or not is
made somewhere in /etc/pam.d/. While looking through the files
I noticed that the runuser-l file in this directory (but not
runuser) contains this line:

-session        optional        pam_systemd.so

While this may seem like it should be the solution, runuser -l
still doesn't start/attach to the user session. So the purpose
of this extra line is still a mystery to me.

For completeness, let me mention /usr/share/pam-configs/systemd
which seems related but I am not sure how.


-- Package-specific info:

-- System Information:
Debian Release: 8.2
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages systemd depends on:
ii  acl             2.2.52-2
ii  adduser         3.113+nmu3
ii  initscripts     2.88dsf-59
ii  libacl1         2.2.52-2
ii  libaudit1       1:2.4-1+b1
ii  libblkid1       2.25.2-6
ii  libc6           2.19-18+deb8u1
ii  libcap2         1:2.24-8
ii  libcap2-bin     1:2.24-8
ii  libcryptsetup4  2:1.6.6-5
ii  libgcrypt20     1.6.3-2
ii  libkmod2        18-3
ii  liblzma5        5.1.1alpha+20120614-2+b3
ii  libpam0g        1.1.8-3.1
ii  libselinux1     2.3-2
ii  libsystemd0     215-17+deb8u2
ii  mount           2.25.2-6
ii  sysv-rc         2.88dsf-59
ii  udev            215-17+deb8u2
ii  util-linux      2.25.2-6

Versions of packages systemd recommends:
ii  dbus            1.8.20-0+deb8u1
ii  libpam-systemd  215-17+deb8u2

Versions of packages systemd suggests:
pn  systemd-ui  <none>

-- no debconf information