initrd-util.sh

#!/bin/sh
#
# $Id: initrd-util,v 1.4 2004/03/23 20:54:58 jmates Exp $
#
# The author disclaims all copyrights and releases this script into the
# public domain.
#
# Utility to assist working with Linux initrd image files.

print_usage () {
  echo "usage: $BASENAME pack|unpack action-arg" >&2
  exit 1
}

ASROOT=sudo
BASENAME=initrd-util
TMPDIR=/var/tmp

if [ -z "$1" ]; then
  print_usage
fi

if [ `id -u` -eq 0 ]; then
  ASROOT=
fi

if [ "$1" = "unpack" ]; then
  if [ -z $2 ]; then
    echo "usage: $BASENAME unpack /path/to/initrd.gz" >&2
    exit 1
  fi

  # assume input is gzip'ed initrd image filepath, uncompress somewhere
  INITRD_RAW=`mktemp $TMPDIR/$BASENAME.initrd-old.XXXXXXX` || exit 1
  gunzip -c $2 > $INITRD_RAW || exit 1

  # area to mount initrd image to
  ORIG_IMAGE_MNT=`mktemp -d $TMPDIR/$BASENAME.mnt-old.XXXXXXX` || exit 1
  chmod 755 $ORIG_IMAGE_MNT
  $ASROOT mount -o loop $INITRD_RAW $ORIG_IMAGE_MNT || exit 1

  # copy initrd contents to working area
  WORK_DIR=`mktemp -d $TMPDIR/$BASENAME.workdir.XXXXXXX` || exit 1
  chmod 755 $WORK_DIR
  $ASROOT rsync -a $ORIG_IMAGE_MNT/ $WORK_DIR || exit 1
  echo "info: initrd $1 expanded into: $WORK_DIR" >&2

  # unpack modules for easy editing
  (
    cd $WORK_DIR || exit 1

    # need to track what new files are added so pack can clean them out
    FILELIST=`ls -A1`

    gunzip -c modules/modules.cgz | sudo cpio -id -m >/dev/null 2>&1
    STATUS=$?
    if [ $STATUS -ne 0 ]; then
      echo "error: non-zero exit ($STATUS) on expansion of modules/modules.cgz" >&2
      exit 1
    fi

    # compare new directory contents with previous, save to file for
    # future reference by 'pack' option to this script
    NEW_STUFF_TMP=`mktemp $TMPDIR/$BASENAME.initrd-tmp.XXXXXXX` || exit 1
    (
      ls -A1

      OLDIFS=$IFS
      IFS=" "
      for e in "$FILELIST"; do
        echo $e;
      done
      IFS=$OLDIFS
    ) | sort | uniq -u > $NEW_STUFF_TMP
    $ASROOT mv $NEW_STUFF_TMP .delete-before-pack
  )
  
  # cleanup temporary stuff
  $ASROOT umount $ORIG_IMAGE_MNT
  rm $INITRD_RAW
  rmdir $ORIG_IMAGE_MNT

  # so can cd on last line of output to stdout
  # e.g. cd `initrd-util unpack initrd.gz | tail -1`
  echo $WORK_DIR
  exit
fi

if [ "$1" = "pack" ]; then
  if [ -z $2 ]; then
    echo "usage: $BASENAME pack /path/to/workdir" >&2
    exit 1
  fi

  if [ ! -d $2 ]; then
    echo "error: not a directory: $2" >&2
    exit 1
  fi

  # delete expanded files recorded by 'unpack' above
  (
    cd $2 || exit 1
    if [ -f .delete-before-pack ]; then
      (
        cat .delete-before-pack
        echo .delete-before-pack
      ) | xargs $ASROOT rm -rf
    fi
  )

  # this might be needed if one is building a new RedHat distribution;
  # otherwise, updating the buildstamp file makes the install unhappy,
  # as I think the date gets compared with other timestamps in later
  # stage files
  #BUILDSTAMP=`mktemp $TMPDIR/$BASENAME.tmp-bs.XXXXXXX` || exit 1
  #chmod 644 $BUILDSTAMP
  #date +%Y%m%d%H%M > $BUILDSTAMP
  #echo Red Hat Linux >> $BUILDSTAMP
  #echo 9 >> $BUILDSTAMP
  #$ASROOT mv $BUILDSTAMP $2/.buildstamp

  # find size of, format new file for image
  #
  # KLUGE need to increase the size of the resulting image file a little
  # as otherwise see problems; still could be boundary conditions here??
  INITRD_SIZE=`$ASROOT du -k -s $2 | awk '{print int($1/1024+2)*1024}'`
  echo "notice: new initrd size: ${INITRD_SIZE}K" >&2

  INITRD_RAW=`mktemp $TMPDIR/$BASENAME.initrd-new.XXXXXXX` || exit 1

  dd if=/dev/zero bs=1024 count=$INITRD_SIZE of=$INITRD_RAW || exit 1
  echo y | mke2fs $INITRD_RAW >/dev/null || exit 1

  # mount point for new image file, copy files into it
  NEW_IMAGE_MNT=`mktemp -d $TMPDIR/$BASENAME.mnt-new.XXXXXXX` || exit 1
  chmod 755 $NEW_IMAGE_MNT
  $ASROOT mount -o loop $INITRD_RAW $NEW_IMAGE_MNT || exit 1

  $ASROOT rsync -a $2/ $NEW_IMAGE_MNT || exit 1

  # cleanup
  $ASROOT sync
  $ASROOT umount $NEW_IMAGE_MNT
  rmdir $NEW_IMAGE_MNT

  gzip -n -9 $INITRD_RAW || exit 1
  chmod 644 $INITRD_RAW.gz
  echo "info: initrd packed into: $INITRD_RAW.gz" >&2
  echo $INITRD_RAW.gz

  exit
fi

# handler routines must exit to avoid hitting this!
print_usage