[systemd-devel] "dev-xxx.device" is trying to start indefinitely long

[Martin Pitt]

Hello Anton,

Anton Gerasimov [2016-09-19 18:08 +0200]:
> I'm trying to make some custom initramfs image with systemd and I
> encounter very strange behaviour. Namely, when I boot into it with
> "root=/dev/hda" kernel command line option the boot process stops right
> after "Reached target Basic System" trying to start dev-hda.device, i.e
> I see "A start job is running for dev-hda.device (1min 8s / no limit)"
> forever.
> 
> However, if I break the boot process on an early stage and run the
> rescue shell, I can see /dev/hda and it can also be mounted without any
> problem. But if I 'systemctl start dev-hda.device' manually it also
> waits forever.
> 
> Have anyone here encountered something similar and what dev-hda.device
> unit is actually trying to do? Could you give me any tips for debugging
> this?

Actually yes. Occasionally our upstream CI fails with a similar
problem where it indefinitely hangs waiting for dev-ttyS0.device; and
just today I got a bug report with a similar symptom like your's [2].
Apparently udev sometimes misses to attach the "systemd" tag to that
device which causes systemd to never "see" it.  We don't understand
the bug at all yet, nor are able to reproduce it with reasonable
effort.

Does your problem happen at every boot, or only sometimes? In the
former case it might actually not be a race condition but a more
systematic error, such as missing some udev rules, or not
re-triggering all udev devices during boot, etc.

Martin

[1] https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-xenial-pitti-systemd-semaphore/xenial/i386/s/systemd-upstream/20160903_005404@/log.gz
[2] https://bugs.launchpad.net/bugs/1625217
-- 
Martin Pitt                        | http://www.piware.de
Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)