modules.d/99img-lib/img-lib.sh

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