libvirt hooks run without bash context

[adamlwgriffiths]

Describe the bug
This bug is partially related to #51152, in that a declarative method of adding the hooks would solve this.

Hooks (eg /var/lib/libvirt/hooks/qemu) normally start with #!/usr/bin/env bash.
It seems this isn't valid within the libvirt context and causes the hook execution - and therefore the vm - to fail.

Instead I have had to work around this by using #!/run/current-system/sw/bin/bash.

To Reproduce
Steps to reproduce the behavior:

1. Copy hook script from here https://github.com/PassthroughPOST/VFIO-Tools/blob/master/libvirt_hooks/qemu to /var/lib/libvirt/hooks/qemu
2. sudo systemctl restart libvirtd.service
3. Run a VM
4. VM fails with an error

Expected behavior
VM starts without error

Screenshots

Additional context

• Using #!/usr/bin/env bash does not fix the issue
• Using #!/run/current-system/sw/bin/bash does fix the issue.

This also applies to all hook scripts that are in turn executed by the hook itself.
Eg. qemu.d/<vm>/prepare/begin/start.sh.

Notify maintainers
@fpletz

Metadata
$ nix-shell -p nix-info --run "nix-info -m"

• system: "x86_64-linux"
• host os: Linux 5.4.62, NixOS, 20.03.2913.4bd1938e03e (Markhor)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3.6
• channels(root): "home-manager-20.03, nixos-20.03.2913.4bd1938e03e"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute: libvirt
# a list of nixos modules affected by the problem
module:

[cole-h]

FWIW, I work around this by simply excluding the shebang(s):

https://github.com/cole-h/nixos-config/blob/69c1a768b210c3b8e29075a8c53ce741f475c0b9/hosts/scadrial/modules/libvirt/default.nix#L4

Not really a solution, but a(nother) workaround for the time being.

[stale]

I marked this as stale due to inactivity. → More info

[adamlwgriffiths]

Still important to me

[tgharib]

I just came across the same issue. Thank you cole-h for the reference nix configuration.

[cole-h]

FWIW, I've slightly changed how I do this: https://github.com/cole-h/nixos-config/blob/61d17a3355288872e4b765ddce1700654a9accc8/hosts/scadrial/modules/libvirt/default.nix#L5-L16

[adamlwgriffiths]

Thanks @cole-h, I didn't realise modprobe would also be unavailable to my hooks.
I've now gotten them working with the following mod from your linked nix files.
Super awesome, since I've been trying to get this working for over a year.

  systemd.services.libvirtd = {
    path = let
      env = pkgs.buildEnv {
        name = "qemu-hook-env";
        paths = with pkgs; [
          bash
          libvirt
          kmod
          systemd
        ];
      };
    in [ env ];
  };

[stale]

I marked this as stale due to inactivity. → More info