Is it possible to hibernate with swap-file?

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1

Hello everyone,

One one of my nixos installation I’m using swapfile and noticed that hibernation never works.
I made sure that resume=/var/swap-file and resume_offset=myoffset are present in my kernel boot args.
I did calculate resume_offset using filefrag -v /var/swapfile | awk '{if($1=="0:"){print $4}}' as per information that i found on arch wiki Power management/Suspend and hibernate - ArchWiki.

I also noticed that in init script following lines:

# Clear the resume device.
if test -n "$resumeDevice"; then
    mkswap "$resumeDevice" || echo 'Failed to clear saved image.'
fi

Does this mean that swap device will be always flushed?

Here is relevant part of my configuration:

  boot.kernelParams = [  "resume=/var/swapfile" "resume_offset=450560" ];
  swapDevices = [ { device = "/var/swapfile"; size = 32768; } ];
  boot.resumeDevice = "/var/swapfile";

I’m currently using nixos-unstable channel with 5.0+ kernel version.

Any information would help me understand what is going on better.

Thank you very much in advance!

3 Likes
2

Ok, this was a problem on my end.

boot.resumeDevice = "/dev/mapper/myroot";

Is the correct option, no need for resume=/var/swapfile in boot.kernelParams also.
resumeDevice should be pointing at partition that swap file resides on.

More info can be found here:

https://www.kernel.org/doc/Documentation/power/swsusp-and-swap-files.txt

4 Likes
3

Hi everyone

I got it to work with a complex setup so I thought I would leave this here for the future generations.

My setup is Btrfs + LUKS2 + TPM unlock + swapfile. Long story short, I got to this setup by doing the recommended auto partitioning during the install, then a long time later I changed things up. I used a live USB NixOS, removed my swap partition and filled the space with the root partition in gparted (leaving a few megabytes at the end empty). I followed a guide to convert from ext4 to btrfs and another guide to upgrade to LUKS2 from the default LUKS1 and also switched to a stronger key algo there. The TPM enrolling is pretty simple too.

Btrfs convert guide
Luks upgrade guide
TPM enroll guide

I only have 2 partitions, the boot and the root. During the boot sequence the encrypted root volume gets automatically unlocked using the TPM and mapped to /dev/dm-0. I found this with ll /dev/mapper/luks*

I have an 18G swapfile at /var/swapfile. It’s auto created by my NixOS config.
I used btrfs inspect-internal map-swapfile -r /var/swapfile to get the resume offset for the kernel parameter.

Here’s my config:

  swapDevices = [ { device = "/var/swapfile"; size = 18*1024; } ];
  boot.resumeDevice = "/dev/dm-0";  # the unlocked drive mapping
  boot.kernelParams = [
    "resume_offset=10134041"
  ];

After building and rebooting I can finally hibernate with systemctl hibernate and my PC wakes up from keyboard or mouse input.

I still don’t know how to add a hibernate button to the shutdown menu and disable the wake from mouse/keyboard but it’s good progress for day.
I’m planning to try Suspend then hibernate - #5 by ericgundrum next