/usr/lib/dracut/modules.d/99img-lib/img-lib.sh is in dracut-core 047-2.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 | #!/bin/sh
# img-lib.sh: utilities for dealing with archives and filesystem images.
#
# TODO: identify/unpack rpm, deb, maybe others?
# super-simple "file" that only identifies archives.
# works with stdin if $1 is not set.
det_archive() {
# NOTE: echo -e works in ash and bash, but not dash
local bz="BZh" xz="$(echo -e '\xfd7zXZ')" gz="$(echo -e '\x1f\x8b')" zs="$(echo -e '0xFD2FB528')"
local headerblock="$(dd ${1:+if=$1} bs=262 count=1 2>/dev/null)"
case "$headerblock" in
$xz*) echo "xz" ;;
$gz*) echo "gzip" ;;
$bz*) echo "bzip2" ;;
$zs*) echo "zstd" ;;
07070*) echo "cpio" ;;
*ustar) echo "tar" ;;
esac
}
# determine filesystem type for a filesystem image
det_fs_img() {
local dev=$(losetup --find --show "$1") rv=""
det_fs $dev; rv=$?
losetup -d $dev
return $rv
}
# unpack_archive ARCHIVE OUTDIR
# unpack a (possibly compressed) cpio/tar archive
unpack_archive() {
local img="$1" outdir="$2" archiver="" decompr=""
local ft="$(det_archive $img)"
case "$ft" in
xz|gzip|bzip2|zstd) decompr="$ft -dc" ;;
cpio|tar) decompr="cat";;
*) return 1 ;;
esac
ft="$($decompr $img | det_archive)"
case "$ft" in
cpio) archiver="cpio -iumd" ;;
tar) archiver="tar -xf -" ;;
*) return 2 ;;
esac
mkdir -p $outdir
( cd $outdir; $decompr | $archiver 2>/dev/null ) < $img
}
# unpack_fs FSIMAGE OUTDIR
# unpack a filesystem image
unpack_fs() {
local img="$1" outdir="$2" mnt="$(mkuniqdir /tmp unpack_fs.)"
mount -o loop $img $mnt || { rmdir $mnt; return 1; }
mkdir -p $outdir; outdir="$(cd $outdir; pwd)"
copytree $mnt $outdir
umount $mnt
rmdir $mnt
}
# unpack an image file - compressed/uncompressed cpio/tar, filesystem, whatever
# unpack_img IMAGEFILE OUTDIR
unpack_img() {
local img="$1" outdir="$2"
[ -r "$img" ] || { warn "can't read img!"; return 1; }
[ -n "$outdir" ] || { warn "unpack_img: no output dir given"; return 1; }
if [ "$(det_archive $img)" ]; then
unpack_archive "$@" || { warn "can't unpack archive file!"; return 1; }
else
unpack_fs "$@" || { warn "can't unpack filesystem image!"; return 1; }
fi
}
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