[systemd-devel] [PATCH] correctly mark system reboot

[Andrey Borzenkov]

On Thu, Mar 3, 2011 at 7:51 AM, Andrey Borzenkov <arvidjaar at gmail.com> wrote:
> On Thu, Mar 3, 2011 at 12:31 AM, Lennart Poettering
> <lennart at poettering.net> wrote:
>> On Wed, 02.03.11 11:41, Andrey Borzenkov (arvidjaar at gmail.com) wrote:
>>
>>> It is expected that system will put "reboot" in wtmp to mark
>>> when it starts coming up. This is looked for by "who -b" and is
>>> used by "last" to calculate correct time spent by various programs.
>>> Add systemd-update-utmp-reboot.service which is started as soon
>>> as possible after local-fs.target to mark reboot.
>>
>> Hmm, systemd-update-utmp-runlevel.service should normally do that
>> implicitly. When /lib/systemd/systemd-update-utmp is called with the
>> "runlevel" argument then it will add the "reboot" entry if necessary
>> automatically, followed by the "runlevel" entry.
>>
>> Are you suggesting that this automatic logic isn't working correctly?
>>
>
> On my notebook "reboot" line is never added. What is funny, it appears
> that on my test VM which has stripped down installation "reboot" does
> actually appear. Which suggests some race condition or uninitialized
> variable somewhere.
>

Well, the problem is, on my notebook it *does* find previous runlevel
entry and so never triggers on_reboot:

Mar  3 09:00:47 cooker systemd-update-utmp[2481]: After utmpxname
Mar  3 09:00:47 cooker systemd-update-utmp[2481]: Found runlevel/previouos: 0/0
Mar  3 09:00:47 cooker systemd-update-utmp[2481]: Previous runlevel: 0
Mar  3 09:00:47 cooker systemd-update-utmp[2481]: Current runlevel: 53
Mar  3 09:00:47 cooker systemd-update-utmp[2481]: After utmpxname
Mar  3 09:00:47 cooker systemd-update-utmp[2481]: Found runlevel/previouos: 0/0

Because it works on stripped down installation, it appears that some
package puts this entry there on startup.

I really do not know how to find who is messing up with utmp; it may
be anything. So it looks like one of

- use explicit unit for "reboot" (and remove current magic from on_runlevel).

- call on_reboot() if previous run-level found was 0.

Personally I find explicit unit to be better understandable and easier
to debug than hiding some magic inside binary that no one is aware of.