Bug#756903: systemd: Boot hangs if filesystems unavailable

[Zbigniew Jędrzejewski-Szmek]

On Fri, Aug 22, 2014 at 01:51:56PM -0400, Stefan Monnier wrote:
> >> In which way is it "safe and correct" to interrupt the boot in this case?
> > In the way that missing some mounts may indicate a serious problem and
> > could lead to incorrect behaviour or data loss.
> 
> Haven't heard many complaints about that over the years, so it shouldn't
> be a super-top-priority goal, I think.
It is one of the mail goals of systemd to use the dependencies. In the
end this is what allows us to achieve reliability.

> In any case, that's not incompatible with the desire to "boot enough for
> remote maintenance to be possible".
> 
> > stopped when something important fails. You can configure things
> > otherwise, but the default is to strictly obey dependencies.
> 
> To get the best of both worlds, I suggest that if a problem happens
> during boot, systemd doesn't just interrupt the boot, but instead tries
> to keep booting up to a "fallback/safe" state, so that maintenance can be
> done conveniently over the network, instead of having to be done "on
> console" which is all too often completely unworkable.
Yes, you can configure such behaviour. You can add OnFailure= and
OnFailureJobMode= to default.target (e.g. in
/etc/systemd/system/default.target.d/failure.conf') to launch some
target you define, and add e.g. sshd.service and other things to this
target. It is hard to do something like this in a general way though.

You can also add nofail where necessary.

In systemd git, there's a more general setting StartTimeoutAction= [1]
which makes it possible to configure an action that will fire also
when boot "hangs" wait for password input or similar.

[1] http://cgit.freedesktop.org/systemd/systemd/commit/?id=2928b0a863

Zbyszek