nixos/kubo: unmount on service stop

When kubo is force killed with `pkill -KILL ipfs` or by systemd-oomd,
it doesn't unmount /ipfs and /ipns. That prevents it
from starting up the next time. So, unmount on postStop.

nixos/doc/manual/release-notes/rl-2305.section.md

@@ -332,6 +332,8 @@ In addition to numerous new and upgraded packages, this release has the followin
     [headscale's example configuration](https://github.com/juanfont/headscale/blob/main/config-example.yaml)
     can be directly written as attribute-set in Nix within this option.
 
+- `services.kubo` unmounts `ipfsMountDir` and `ipnsMountDir` even if it is killed uncleanly, when 'autoMount` is enabled.
+
 - `nixos/lib/make-disk-image.nix` can now mutate EFI variables, run user-provided EFI firmware or variable templates. This is now extensively documented in the NixOS manual.
 
 - `services.grafana` listens only on localhost by default again. This was changed to upstreams default of `0.0.0.0` by accident in the freeform setting conversion.

nixos/modules/services/network-filesystems/kubo.nix

@@ -319,6 +319,10 @@ in
           # change when the changes are applied. Whyyyyyy.....
           ipfs --offline config replace -
       '';
+      postStop = mkIf cfg.autoMount ''
+        # After an unclean shutdown the fuse mounts at ${cfg.ipnsMountDir} and ${cfg.ipfsMountDir} are locked
+        umount --quiet '${cfg.ipnsMountDir}' '${cfg.ipfsMountDir}' || true
+      '';
       serviceConfig = {
         ExecStart = [ "" "${cfg.package}/bin/ipfs daemon ${kuboFlags}" ];
         User = cfg.user;