[Pkg-utopia-maintainers] Bug#833318: /etc/X11/Xsession.d/95dbus_update-activation-env: dbus-update-activation-environment --systemd always fails without dbus-user-session package installed

[Mirosław Zalewski]

Package: dbus-x11
Version: 1.10.8-1
Severity: normal
File: /etc/X11/Xsession.d/95dbus_update-activation-env

Dear Maintainer,

`dbus-update-activation-environment --systemd` fails on systems without
dbus-user-session package installed. This limits usefulness of
`/etc/X11/Xsession.d/95dbus_update-activation-env` file and renders
comment there misleading.

   * What led up to the situation?

I was trying to understand why `systemctl --user show-environment`
prints only very limited number of variables and why this happens:

#v+
dbus-update-activation-environment --all --systemd        
dbus-update-activation-environment: warning: error sending to systemd: org.freedesktop.DBus.Error.Spawn.ChildExited: Process org.freedesktop.systemd1 exited with status 1
#v-


   * What exactly did you do (or not do) that was effective (or
     ineffective)?

Comment in `/etc/X11/Xsession.d/95dbus_update-activation-env` says that
Xsession environment variables will be put in "systemd --user, if
running". Therefore, I expected all variables defined there to be
available in systemd user services. Since they were not, I thought that
maybe systemd --user starts only after dbus-launch, but that seems to
not be a case:

#v+
ps -o pid,user,args -C dbus-launch -C systemd
  PID USER     COMMAND
    1 root     /sbin/init
 4079 sddm     /lib/systemd/systemd --user
 4090 sddm     dbus-launch --autolaunch 60bcc674655243c8a520cc5813fe7172 --binary-syntax --close-stderr
 4138 minio    /lib/systemd/systemd --user
 4200 minio    /usr/bin/dbus-launch --exit-with-session --sh-syntax
#v-

After some search, I finally looked up `dbus-update-activation-environment` 
source code. This error message comes from line 399, which handles
return value of dbus call to `org.freedesktop.systemd1` service on
connection defined as `dbus_bus_get (DBUS_BUS_SESSION, &error);`. I can
only assume that tool is trying to talk to systemd on session bus.
However, `org.freedesktop.systemd1` service is available only on system
bus (and seems to refer to system's systemd, not user instance) - not on
session bus. I can verify that by using `qdbusviewer` tool.

After installing `dbus-user-session` package, I can find
`org.freedesktop.systemd1` on session bus, `systemctl --user show-environment` 
prints many variables and `dbus-update-activation-environment --all --systemd`
call does not print any error message.

   * What outcome did you expect instead?

systemd --user instance to be populated with Xsession variables by
default, OR `/etc/X11/Xsession.d/95dbus_update-activation-env` file not
misleading me into thinking that systemd should have these variables
defined. Rephrasing comment to say that only dbus environment is
changed, and `dbus-user-session` must be installed for systemd --user
instance, would be very much appreciated.


-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (990, 'testing'), (400, 'unstable'), (102, 'experimental'), (10, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.6.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=pl_PL.UTF-8, LC_CTYPE=pl_PL.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to pl_PL.UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages dbus-x11 depends on:
ii  dbus         1.10.8-1
ii  libc6        2.23-2
ii  libdbus-1-3  1.10.8-1
ii  libx11-6     2:1.6.3-1

dbus-x11 recommends no packages.

dbus-x11 suggests no packages.

-- no debconf information