Image with btrfs rootfs doesn't boot in qemu vm

[kurnevsky]

My earlier comment: #356 (comment)

I'm trying to boot into qemu vm using an image with btrfs rootfs. Here is what I tried: kurnevsky/nixfiles@6f84f88 - before this change it worked, and it works if I just change fs type to ext4.

Here are my full configs I used, just for the reference:
https://github.com/kurnevsky/nixfiles/blob/phone-btrfs/modules/phone.nix
https://github.com/kurnevsky/nixfiles/blob/phone-btrfs/machines/phone/configuration.nix
https://github.com/kurnevsky/nixfiles/blob/phone-btrfs/flake.nix#L152

In the qemu vm logs I see (after running ./result):

modprobe: module btrfs not found in modules.dep
W, [2023-03-07T12:58:01.179669//1.6682 #1]  WARN -- : Kernel filesystem module “btrfs” failed to load.
mount: mounting /dev/disk/by-uuid/e3b552a3-be28-4d1d-9016-e1b9a8699464 on /mnt/ failed: No such device

[kurnevsky]

Specifying mobile.boot.stage-1.kernel.additionalModules = [ "btrfs" ]; fixed the problem.

[kurnevsky]

Though now home-manager complains: error: could not set permissions on '/nix/var/nix/profiles/per-user' to 755: Operation not permitted

[kurnevsky]

It executes nix-build --expr '{}' --no-out-link which fails on btrfs. And this happens because nix daemon didn't start: Nix Daemon was skipped because of an unmet condition check (ConditionPathIsReadWrite=/nix/var/nix/daemon-socket). This is quite strange, because this path is writable.

[kurnevsky]

Looks like this

mobile-nixos/lib/image-builder/makeBtrfs.nix

Line 12 in ba46388

-r . \

copies owner as well, which is wrong...

[kurnevsky]

Yep, that's the reason - if I change owner to root it works.

[kurnevsky]

It seems the only way to fix this is to patch these lines: https://github.com/kdave/btrfs-progs/blob/d1d8fb4b599e76a3d6bc355df9e5787955104a72/mkfs/rootdir.c#L128-L129

Or, maybe some hack with linux vm...