mirror of
https://github.com/ilyakooo0/nixpkgs.git
synced 2024-11-15 03:15:56 +03:00
92 lines
3.3 KiB
Nix
92 lines
3.3 KiB
Nix
# Builds an ext4 image containing a populated /nix/store with the closure
|
||
# of store paths passed in the storePaths parameter, in addition to the
|
||
# contents of a directory that can be populated with commands. The
|
||
# generated image is sized to only fit its contents, with the expectation
|
||
# that a script resizes the filesystem at boot time.
|
||
{ pkgs
|
||
# List of derivations to be included
|
||
, storePaths
|
||
# Shell commands to populate the ./files directory.
|
||
# All files in that directory are copied to the root of the FS.
|
||
, populateImageCommands ? ""
|
||
, volumeLabel
|
||
, uuid ? "44444444-4444-4444-8888-888888888888"
|
||
, e2fsprogs
|
||
, libfaketime
|
||
, perl
|
||
, lkl
|
||
}:
|
||
|
||
let
|
||
sdClosureInfo = pkgs.buildPackages.closureInfo { rootPaths = storePaths; };
|
||
in
|
||
|
||
pkgs.stdenv.mkDerivation {
|
||
name = "ext4-fs.img";
|
||
|
||
nativeBuildInputs = [e2fsprogs.bin libfaketime perl lkl];
|
||
|
||
buildCommand =
|
||
''
|
||
(
|
||
mkdir -p ./files
|
||
${populateImageCommands}
|
||
)
|
||
# Add the closures of the top-level store objects.
|
||
storePaths=$(cat ${sdClosureInfo}/store-paths)
|
||
|
||
# Make a crude approximation of the size of the target image.
|
||
# If the script starts failing, increase the fudge factors here.
|
||
numInodes=$(find $storePaths ./files | wc -l)
|
||
numDataBlocks=$(du -s -c -B 4096 --apparent-size $storePaths ./files | tail -1 | awk '{ print int($1 * 1.03) }')
|
||
bytes=$((2 * 4096 * $numInodes + 4096 * $numDataBlocks))
|
||
echo "Creating an EXT4 image of $bytes bytes (numInodes=$numInodes, numDataBlocks=$numDataBlocks)"
|
||
|
||
truncate -s $bytes $out
|
||
faketime -f "1970-01-01 00:00:01" mkfs.ext4 -L ${volumeLabel} -U ${uuid} $out
|
||
|
||
# Also include a manifest of the closures in a format suitable for nix-store --load-db.
|
||
cp ${sdClosureInfo}/registration nix-path-registration
|
||
cptofs -t ext4 -i $out nix-path-registration /
|
||
|
||
# Create nix/store before copying paths
|
||
faketime -f "1970-01-01 00:00:01" mkdir -p nix/store
|
||
cptofs -t ext4 -i $out nix /
|
||
|
||
echo "copying store paths to image..."
|
||
cptofs -t ext4 -i $out $storePaths /nix/store/
|
||
|
||
(
|
||
echo "copying files to image..."
|
||
cd ./files
|
||
cptofs -t ext4 -i $out ./* /
|
||
)
|
||
|
||
# I have ended up with corrupted images sometimes, I suspect that happens when the build machine's disk gets full during the build.
|
||
if ! fsck.ext4 -n -f $out; then
|
||
echo "--- Fsck failed for EXT4 image of $bytes bytes (numInodes=$numInodes, numDataBlocks=$numDataBlocks) ---"
|
||
cat errorlog
|
||
return 1
|
||
fi
|
||
|
||
(
|
||
# Resizes **snugly** to its actual limits (or closer to)
|
||
free=$(dumpe2fs $out | grep '^Free blocks:')
|
||
blocksize=$(dumpe2fs $out | grep '^Block size:')
|
||
blocks=$(dumpe2fs $out | grep '^Block count:')
|
||
blocks=$((''${blocks##*:})) # format the number.
|
||
blocksize=$((''${blocksize##*:})) # format the number.
|
||
# System can't boot with 0 blocks free.
|
||
# Add 16MiB of free space
|
||
fudge=$(( 16 * 1024 * 1024 / blocksize ))
|
||
size=$(( blocks - ''${free##*:} + fudge ))
|
||
|
||
echo "Resizing from $blocks blocks to $size blocks. (~ $((size*blocksize/1024/1024))MiB)"
|
||
EXT2FS_NO_MTAB_OK=yes resize2fs $out -f $size
|
||
)
|
||
|
||
# And a final fsck, because of the previous truncating.
|
||
fsck.ext4 -n -f $out
|
||
'';
|
||
}
|