mirror of
https://github.com/NixOS/nixpkgs.git
synced 2024-11-25 07:00:43 +00:00
89 lines
3.6 KiB
Nix
89 lines
3.6 KiB
Nix
# Builds an ext4 image containing a populated /nix/store with the closure
|
|
# of store paths passed in the storePaths parameter. The generated image
|
|
# is sized to only fit its contents, with the expectation that a script
|
|
# resizes the filesystem at boot time.
|
|
{ pkgs
|
|
, storePaths
|
|
, volumeLabel
|
|
}:
|
|
|
|
pkgs.stdenv.mkDerivation {
|
|
name = "ext4-fs.img";
|
|
|
|
nativeBuildInputs = with pkgs; [e2fsprogs libfaketime perl];
|
|
|
|
# For obtaining the closure of `storePaths'.
|
|
exportReferencesGraph =
|
|
map (x: [("closure-" + baseNameOf x) x]) storePaths;
|
|
|
|
buildCommand =
|
|
''
|
|
# Add the closures of the top-level store objects.
|
|
storePaths=$(perl ${pkgs.pathsFromGraph} closure-*)
|
|
|
|
# Also include a manifest of the closures in a format suitable
|
|
# for nix-store --load-db.
|
|
printRegistration=1 perl ${pkgs.pathsFromGraph} closure-* > nix-path-registration
|
|
|
|
# Make a crude approximation of the size of the target image.
|
|
# If the script starts failing, increase the fudge factors here.
|
|
numInodes=$(find $storePaths | wc -l)
|
|
numDataBlocks=$(du -c -B 4096 --apparent-size $storePaths | awk '$2 == "total" { 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 44444444-4444-4444-8888-888888888888 $out
|
|
|
|
# Populate the image contents by piping a bunch of commands to the `debugfs` tool from e2fsprogs.
|
|
# For example, to copy /nix/store/abcd...efg-coreutils-8.23/bin/sleep:
|
|
# cd /nix/store/abcd...efg-coreutils-8.23/bin
|
|
# write /nix/store/abcd...efg-coreutils-8.23/bin/sleep sleep
|
|
# sif sleep mode 040555
|
|
# sif sleep gid 30000
|
|
# In particular, debugfs doesn't handle absolute target paths; you have to 'cd' in the virtual
|
|
# filesystem first. Likewise the intermediate directories must already exist (using `find`
|
|
# handles that for us). And when setting the file's permissions, the inode type flags (__S_IFDIR,
|
|
# __S_IFREG) need to be set as well.
|
|
(
|
|
echo write nix-path-registration nix-path-registration
|
|
echo mkdir nix
|
|
echo cd /nix
|
|
echo mkdir store
|
|
|
|
# XXX: This explodes in exciting ways if anything in /nix/store has a space in it.
|
|
find $storePaths -printf '%y %f %h %m\n'| while read -r type file dir perms; do
|
|
# echo "TYPE=$type DIR=$dir FILE=$file PERMS=$perms" >&2
|
|
|
|
echo "cd $dir"
|
|
case $type in
|
|
d)
|
|
echo "mkdir $file"
|
|
echo sif $file mode $((040000 | 0$perms)) # magic constant is __S_IFDIR
|
|
;;
|
|
f)
|
|
echo "write $dir/$file $file"
|
|
echo sif $file mode $((0100000 | 0$perms)) # magic constant is __S_IFREG
|
|
;;
|
|
l)
|
|
echo "symlink $file $(readlink "$dir/$file")"
|
|
;;
|
|
*)
|
|
echo "Unknown entry: $type $dir $file $perms" >&2
|
|
exit 1
|
|
;;
|
|
esac
|
|
|
|
echo sif $file gid 30000 # chgrp to nixbld
|
|
done
|
|
) | faketime -f "1970-01-01 00:00:01" debugfs -w $out -f /dev/stdin > errorlog 2>&1
|
|
|
|
# The debugfs tool doesn't terminate on error nor exit with a non-zero status. Check manually.
|
|
if egrep -q 'Could not allocate|File not found' errorlog; then
|
|
cat errorlog
|
|
echo "--- Failed to create EXT4 image of $bytes bytes (numInodes=$numInodes, numDataBlocks=$numDataBlocks) ---"
|
|
return 1
|
|
fi
|
|
'';
|
|
}
|