pyrox.dev
1# Builds an btrfs image containing a populated /nix/store with the closure
2# of store paths passed in the storePaths parameter, in addition to the
3# contents of a directory that can be populated with commands. The
4# generated image is sized to only fit its contents, with the expectation
5# that a script resizes the filesystem at boot time.
6{ pkgs
7, lib
8# List of derivations to be included
9, storePaths
10# Whether or not to compress the resulting image with zstd
11, compressImage ? false, zstd
12# Shell commands to populate the ./files directory.
13# All files in that directory are copied to the root of the FS.
14, populateImageCommands ? ""
15, volumeLabel
16, uuid ? "44444444-4444-4444-8888-888888888888"
17, btrfs-progs
18, libfaketime
19, fakeroot
20}:
21
22let
23 sdClosureInfo = pkgs.buildPackages.closureInfo { rootPaths = storePaths; };
24in
25pkgs.stdenv.mkDerivation {
26 name = "btrfs-fs.img${lib.optionalString compressImage ".zst"}";
27
28 nativeBuildInputs = [ btrfs-progs libfaketime fakeroot ] ++ lib.optional compressImage zstd;
29
30 buildCommand =
31 ''
32 ${if compressImage then "img=temp.img" else "img=$out"}
33
34 set -x
35 (
36 mkdir -p ./files
37 ${populateImageCommands}
38 )
39
40 mkdir -p ./rootImage/nix/store
41
42 xargs -I % cp -a --reflink=auto % -t ./rootImage/nix/store/ < ${sdClosureInfo}/store-paths
43 (
44 GLOBIGNORE=".:.."
45 shopt -u dotglob
46
47 for f in ./files/*; do
48 cp -a --reflink=auto -t ./rootImage/ "$f"
49 done
50 )
51
52 cp ${sdClosureInfo}/registration ./rootImage/nix-path-registration
53
54 touch $img
55 faketime -f "1970-01-01 00:00:01" fakeroot mkfs.btrfs -L ${volumeLabel} -U ${uuid} -r ./rootImage --shrink $img
56
57 if ! btrfs check $img; then
58 echo "--- 'btrfs check' failed for BTRFS image ---"
59 return 1
60 fi
61
62 if [ ${builtins.toString compressImage} ]; then
63 echo "Compressing image"
64 zstd -v --no-progress ./$img -o $out
65 fi
66 '';
67}