Bug#814758: Case power button is ignored unless dbus is installed.

[Trent W. Buck]

Package: systemd
Version: 215-17+deb8u3
Severity: normal

My computers have physical power buttons on their cases.
When the button is pressed, I want it to initiate a clean shutdown.

On a desktop install, this happens because systemd-logind handles it:

    root at het:~# journalctl -fu systemd-logind
    -- Logs begin at Mon 2016-02-15 15:42:58 AEDT. --
    Feb 15 15:43:08 het systemd-logind[470]: New seat seat0.
    Feb 15 15:43:08 het systemd-logind[470]: Watching system buttons on /dev/input/event1 (Power Button)
    Feb 15 15:43:08 het systemd-logind[470]: Watching system buttons on /dev/input/event5 (Video Bus)
    Feb 15 15:43:08 het systemd-logind[470]: Watching system buttons on /dev/input/event0 (Power Button)
    [...]
    Feb 15 17:50:47 het systemd-logind[470]: Power key pressed.
    Feb 15 17:50:47 het systemd-logind[470]: Powering Off...
    Feb 15 17:50:47 het systemd-logind[470]: System is powering down.

On a server install, this does not happen,
The logs indicate systemd-logind started without issue, then nothing:

    root at alpha-understudy:~# journalctl -u systemd-logind
    -- Logs begin at Mon 2015-11-23 15:29:23 AEDT, end at Mon 2016-02-15 17:45:16 AEDT. --
    Nov 23 15:29:29 alpha-understudy.cyber.com.au systemd[1]: Started Login Service.

However, on closer inspection it has actually failed:

    root at alpha-understudy:~# systemctl status systemd-logind
    ● systemd-logind.service - Login Service
       Loaded: loaded (/lib/systemd/system/systemd-logind.service; static)
       Active: inactive (dead)
               start condition failed at Mon 2015-11-23 15:29:29 AEDT; 2 months 23 days ago
               ConditionPathExists=/lib/systemd/system/dbus.service was not met
         Docs: man:systemd-logind.service(8)
               man:logind.conf(5)
               http://www.freedesktop.org/wiki/Software/systemd/logind
               http://www.freedesktop.org/wiki/Software/systemd/multiseat

    Nov 23 15:29:29 alpha-understudy.cyber.com.au systemd[1]: Started Login Service.

    root at alpha-understudy:~# pgrep logind
    root at alpha-understudy:~# pgrep dbus
    root at alpha-understudy:~# dpkg-query -W '*dbus*'
    dbus
    libdbus-1-3:amd64       1.8.20-0+deb8u1

It's failing because dbus isn't installed.
Installing dbus fixes the problem.

    systemd Recommends: dbus.

    dbus is Priority: standard.

If a system is created with debootstrap,
this means dbus is never installed,
and the power button doesn't work:

    # script -c 'sh -xc "debootstrap jessie /tmp/bootstrap/delete-me http://apt.cyber.com.au/debian"' typescript
    # grep dbus typescript
    [no hits]

I believe debian-install users get Priority: standard packages via tasksel defaults,
though they can opt-out of this.

systemd-logind wants dbus so that shutdown "inhibitors" can be used.


AFAICT these are the available options:

  * change systemd Recommends: dbus to systemd Depends: dbus.

    I strongly dislike this option,
    because it will force dbus & expat on minbase installs.

    (Also, even upstream doesn't say dbus is mandatory.)

  * change systemd so the power button works without dbus.

    I like this best, but I expect upstream to hate it.

  * change systemd so when systemd-logind fails to start (as above),
    it actually SAYS THERE'S A PROBLEM in the journal/syslog.

    I expect upstream to hate this, too.

  * change systemd's Description, and/or the Debian release notes,
    to warn users about this.

  * do nothing.



PS: I used to install acpid & acpi-support-base to work around this issue,
until I discovered that on my faster production hosts,
acpid doesn't start reliably under systemd.
About 48% of the time, acpid starts before /dev/input/ is made, giving:

    acpid: inotify_add_watch() failed: No such file or directory (DIGITS)

Sigh.