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lib/make-ext4-fs: more efficient store maker

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This commit is contained in:
Alexander Krupenkin 2018-12-24 12:20:46 +03:00
parent 98436ba55a
commit 2f0c495c31
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1 changed files with 10 additions and 51 deletions
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61
nixos/lib/make-ext4-fs.nix
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@ -9,6 +9,7 @@
, e2fsprogs
, libfaketime
, perl
, lkl
}:
let
@ -18,16 +19,13 @@ in
pkgs.stdenv.mkDerivation {
name = "ext4-fs.img";
nativeBuildInputs = [e2fsprogs.bin libfaketime perl];
nativeBuildInputs = [e2fsprogs.bin libfaketime perl lkl];
buildCommand =
''
# Add the closures of the top-level store objects.
storePaths=$(cat ${sdClosureInfo}/store-paths)
# Also include a manifest of the closures in a format suitable for nix-store --load-db.
cp ${sdClosureInfo}/registration nix-path-registration
# Make a crude approximation of the size of the target image.
# If the script starts failing, increase the fudge factors here.
numInodes=$(find $storePaths | wc -l)
@ -38,55 +36,16 @@ pkgs.stdenv.mkDerivation {
truncate -s $bytes $out
faketime -f "1970-01-01 00:00:01" mkfs.ext4 -L ${volumeLabel} -U ${uuid} $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
# 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 /
# 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
# 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 "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
echo "copying store paths to image..."
cptofs -t ext4 -i $out $storePaths /nix/store/
# 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