[systemd-devel] Implementing resume from hibernation as a systemd unit file

[Lennart Poettering]

On Fri, 15.08.14 13:54, Ivan Shapovalov (intelfx100 at gmail.com) wrote:

> On Friday 15 August 2014 at 11:32:59, Lennart Poettering wrote:	
> > On Fri, 15.08.14 13:02, Ivan Shapovalov (intelfx100 at gmail.com) wrote:
> > 
> > Ah, well, if the resume= switch is supposed to simply carry the finished
> > device node path, and nothing we still have to translate into one, then
> > of course the entire udev rules step is unnecessary, and you can just
> > write this out directly from the generator.
> 
> Yes, that's how it happens now.
> 
> > 
> > > > > Actually, the main question is how to order the resume unit. It needs to run
> > > > > before any real filesystems are mounted (speaking in terms of initrd) AND before
> > > > > rootfs is remounted read-write (speaking in terms of initrd-less system), but
> > > > > after whatever is needed to make the device node appear.
> > > > 
> > > > You could turn this into a generator, that pulls the switch from the
> > > > kernel cmdline, and generates a service that orders itself before
> > > > local-fs-pre.taret and after the device you need. The device you need
> > > > you give a stable name via an udev rule. 
> > > 
> > > So is "Before=local-fs-pre.target" a sufficient ordering for such resume unit?
> > > 
> > > Again, the resume unit must be started before any filesystems are (re)mounted
> > > read-write, either from initrd or not.
> > 
> > Yes. That should be enough.
> > 
> > > Seems like there's at least systemd-remount-fs.service that also needs to be
> > > taken into account...
> > 
> > That only runs after the transition into the host OS.
> 
> I'd like to make this work both with initramfs and without one (provided that
> the rootfs has been mounted read-only by using 'ro' kernel cmdline parameter).
> 
> In this case, what are the needed orderings?

Actually systemd-remount-fs.service uses After=local-fs-pre.target
anyway, so ordering before l-f-p.t should be enough.


Lennart

-- 
Lennart Poettering, Red Hat