Swapfile start fails on reboot

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1

NixOS v23.05

When I reboot my server I am getting a swapfile start failure during boot. I tried both encrypted and unencrypted and get the same error message. If I run systemct restart mkswap-var-cache-swapfile manually, it succeeds and swap is activated. Journal for the service:

Nov 15 10:50:59 vps mkswap-var-cache-swapfile-start[832]: Attaching loopback device failed (loop device with autoclear flag is required>
Nov 15 10:50:59 vps systemd[1]: mkswap-var-cache-swapfile.service: Main process exited, code=exited, status=1/FAILURE
Nov 15 10:50:59 vps systemd[1]: mkswap-var-cache-swapfile.service: Failed with result 'exit-code'.
Nov 15 10:50:59 vps systemd[1]: Failed to start Initialisation of swap device /var/cache/swapfile.

Swap config:

swapDevices = [ {
    device = "/var/cache/swapfile";
    size = 4*1024;
    randomEncryption.enable = true; 
  } ];

Filesystem is ext4.

Any ideas? Thanks!

2

Well, I seem to have solved this based information here. Added this to the configuration.nix:

systemd.services.mkswap-var-cache-swapfile.unitConfig = {
  Requires = "systemd-tmpfiles-setup-dev.service";
  After = "systemd-tmpfiles-setup-dev.service";
};

Not sure if this a bug worth reporting or an oddity of running on a cloud server (Hetzner)?

3

I would very much like to know why that’s necessary. If the problem can be reproduced, it’d be worth opening an issue.

4

Here is my basic config. Didn’t include the various services cause I doubt they’re relevant. I installed on a Hetzner vps using nixos-infect.

My other nix machines either use zram or a swap partition. This is the only one with a swapfile. Maybe I’ll give it a try in a VM. There were no other similar issues that I could find anywhere!

5

This seems to be fixed in 23.11. I no longer need the extra snippet.