Bash Scripts

chrtsetup

set up mounts and enter a chroot

chrtsetup configuration file to set up a unionfs of a disk image and a filesystem tree:

#!bin/bash

# only $CHROOT and $MOUNTS are relevant to chrtsetup
ROOT=/home/user/ubuntu_unionfs
IMG=$ROOT/ext3_1GB.dd
IMG_MNT=$ROOT/diskimage
SHARED=$ROOT/shared
FS=$ROOT/chroot
CHROOT=$ROOT/chroot

#from           to                      fstype  mount-options   do-chroot
MOUNTS=`echo -e "\
/dev            $CHROOT/dev             none    bind            false   \n\
$ROOT/shared    $CHROOT/root/shared     none    bind            false   \n\
$IMG            $IMG_MNT                ext3    loop            false   \n\
unionfs         $CHROOT                 unionfs dirs=$IMAGE_MNT=rw:$FS=ro false \n\
none            /proc                   proc    defaults        true    \n\
none            /sys                    sysfs   defaults        true    \n\
none            /dev/pts                devpts  defaults        true    \n\

the script:

#!/bin/bash
PREPARE=; ENTER=; CLEAN=; VERBOSE=;
RUN=/bin/bash
CONFIG=

function verbose  { [ $VERBOSE ] && echo $@; $@ 1> /dev/null; }
function warn { [ $VERBOSE ] && echo "warn: $1" >&2; }
function error { echo "error: $1" >&2; exit 1; }
function usage {
  cat <<EOF
Usage: chrtsetup [OPTION] [CHRTCONF]
  -v, --verbose            print actions
  -p, --prepare            perform mount sequence only
  -c, --clean              perform umount sequence only
  -e, --enter              enter chroot only
  -r, --run=COMMAND        run specified COMMAND after entering the chroot

CHRTCONF is the name of the chroot configuration stored in /etc/chrtsetup/.
If neither -p, -c nor -e is set all actions are enabled.

Examples:
  chrtsetup ubuntu      # executed setup defined in /etc/chrtsetup/ubuntu, enter chroot and clean up after
  chrtsetup -c ubuntu   # undo mounts performed to setup the chroot
  chrtsetup -pe ubuntu  # mount, enter but do not clean up after
EOF

  exit 2
}

function chrtify { cmd=$1 doChroot=$2
  if [ "$doChroot" == "true" ]; then 
    echo "chroot -- $CHROOT $cmd"
  else
    echo $cmd
  fi
}

function doUmount { from=$1 to=$2 fstype=$3 opts=$4 doChroot=$5
  umount=`chrtify 'umount' $doChroot`
  verbose $umount -t $fstype $to || error "umount failed: $@"
}

function doMount { from=$1 to=$2 fstype=$3 opts=$4 doChroot=$5
  mount=`chrtify 'mount' $doChroot`
  verbose $mount -t $fstype -o $opts $from $to || error "mount failed: $@"
}

function isMounted { from=$1 to=$2 fstype=$3 opts=$4 doChroot=$5
  grepMounts=`chrtify "grep -qF /etc/mtab -e" $doChroot`
  $grepMounts "$from $to $fstype"
} 

function clean {
  echo "$MOUNTS" | tac | while read mnt; do
    isMounted $mnt && doUmount $mnt \
      || warn "$mnt not mounted" >&2
  done
}

function prepare {
  echo "$MOUNTS" | while read mnt; do
    isMounted $mnt || doMount $mnt \
      && warn "$mnt already mounted" >&2
  done
}

[ $# -eq 0 ] && usage

eval set -- "`getopt -o vpecr --long verbose,prepare,enter,clean,run -n 'chrtsetup' -- \"$@\"`"
while true ; do
        case "$1" in
                -v|--verbose) VERBOSE=0 ; shift ;;
                -p|--prepare) PREPARE=0 ; shift ;;
                -e|--enter) ENTER=0 ; shift ;;
                -c|--clean) CLEAN=0 ; shift ;;
                -r|--run) RUN="$2" ; shift 2;;
                --) shift ; break ;;
        esac
done
CONFIG=$1

[ -z $CONFIG ] && usage
[ ! "$CLEAN" -a ! "$PREPARE" -a  ! "$ENTER" ] && CLEAN=set PREPARE=set ENTER=set

source "/etc/chrtsetup/$CONFIG"

[ $PREPARE ] && prepare
[ $ENTER ]  && chroot "$CHROOT" "$RUN"
[ $CLEAN ]  && clean