Bug#902416: systemd: systemctl hibernate: unable to resume after upgrade

[Mario.Limonciello at dell.com]

> -----Original Message-----
> From: Michael Biebl [mailto:biebl at debian.org]
> Sent: Friday, July 6, 2018 9:53 AM
> To: Limonciello, Mario; joel at kazbak.co.uk; 902416 at bugs.debian.org
> Subject: Re: Bug#902416: systemd: systemctl hibernate: unable to resume after
> upgrade
> 
> Am 06.07.2018 um 14:41 schrieb Mario.Limonciello at dell.com:
> 
> > Yes I could see two swap partitions causing the wrong one to be picked.
> > It's trying to select the bigger of the two.
> >
> > If they don't match the one you're putting in /etc/initramfs-tools/conf.d/resume
> > then that would cause problems.  Please do confirm if you switch what's in
> > initramfs conf.d/resume that the problem is fixed.
> 
> If you have multiple swap partitions and you run
> echo "disk" > /sys/power/state
> which partition does the kernel use?
> 

Whichever one was configured in /sys/power/resume prior to running that command.

The kernel can't know which one /to/ hibernate to unless it was configured in advance.
Just like the initramfs can't know which one to resume /from/ unless it knew which one
it resumed to.

You can confirm which one the kernel is using by turning on debugging for hibernate and looking
for this message:
https://github.com/torvalds/linux/commit/648464076160ee7a4112d05eea13621790ab9d04#diff-4bc504812a6e5edefe9068b56aa3ddf0