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-rwxr-xr-xmkusbimg75
1 files changed, 26 insertions, 49 deletions
diff --git a/mkusbimg b/mkusbimg
index ba1e5c9..727bb80 100755
--- a/mkusbimg
+++ b/mkusbimg
@@ -16,25 +16,6 @@
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
-# next_avail_loop()
-# prints the next available loopback device
-# returns 0 on success
-# 1 on failure
-# XXX: this is only necessary because
-# the cryptoloop patch for losetup
-# destroys losetup -f
-next_avail_loop()
-{
- for i in /dev/loop/*; do
- echo $(losetup -a|cut -d':' -f1) | grep -q $i
- if [ $? -eq 1 ]; then
- echo $i
- return 0
- fi
- done
- return 1
-}
-
# usage(exitvalue)
# outputs a usage message and exits with value
APPNAME=$(basename "${0}")
@@ -50,52 +31,48 @@ if [ $# -ne 2 ]; then
usage 1
fi
-IMG="${2}"
+DISKIMG="${2}"
IMGROOT="${1}"
-LOOPDEV=$(next_avail_loop)
TMPDIR=$(mktemp -d)
+FSIMG=$(mktemp)
-# TODO: there are better ways to do this
-# than adding 25% to the rootsize
-# XXX: doesn't seem to boot if we cut it too
-# close. even if everything fits...
-# IMGSZ >= filesystem overhead + rootsize + 512bytes
-# must hold or there will be insufficient space
+# ext2 overhead's upper bound is 6%
+# empirically tested up to 1GB
rootsize=$(du -bs ${IMGROOT}|cut -f1)
-IMGSZ=$(( (${rootsize}*5)/4 + 512 ))
-
-# create the image file
-dd if=/dev/zero of="$IMG" bs="$IMGSZ" count=1
+IMGSZ=$(( (${rootsize}*106)/100/512 + 1)) # image size in sectors
-# loop mount the disk image
-losetup "$LOOPDEV" "$IMG"
-
-# create a partition table
-# if this looks like voodoo, it's because it is
-echo "63,,,*,"|sfdisk -uS "$LOOPDEV"
+# create the filesystem image file
+dd if=/dev/zero of="$FSIMG" bs=512 count="$IMGSZ"
-# loop mount the partition we just made
-# that magic number (offset in bytes to first partition) is more voodoo
-losetup -d "$LOOPDEV"
-losetup -o32256 "$LOOPDEV" "$IMG"
-
-# create a filesystem on our partition
-mke2fs -m 0 "$LOOPDEV"
+# create a filesystem on the image
+mke2fs -m 0 -F "$FSIMG"
# mount the filesystem and copy data
-mount "$LOOPDEV" "$TMPDIR"
+mount -o loop "$FSIMG" "$TMPDIR"
cp -a "$IMGROOT"/* "$TMPDIR"
-# unmount filesystem and loopback
+# unmount filesystem
umount "$TMPDIR"
-losetup -d "$LOOPDEV"
+
+# add sectors 0-62, then glue together
+dd if=/dev/zero of="$DISKIMG" bs=512 count=63
+cat "$FSIMG" >> "$DISKIMG"
+
+# create a partition table
+# if this looks like voodoo, it's because it is
+sfdisk -uS -f "$DISKIMG" << EOF
+63,$IMGSZ,83,*
+0,0,00
+0,0,00
+0,0,00
+EOF
# install grub on the image
grub --no-floppy --batch << EOF
-device (hd0) $IMG
+device (hd0) $DISKIMG
root (hd0,0)
setup (hd0)
EOF
# all done :)
-rm -fr "$TMPDIR"
+rm -fr "$TMPDIR" "$FSIMG"