Script to manage chroot

enter-chroot.bash

#!/bin/bash

if [ "$UID" != "0" ]
then
     echo "You have to be root" >&2
     exit 1
fi

CHROOT=$1

if [ ! -f $CHROOT.in ]
then
     for mnt in /dev /dev/pts /proc /sys
     do
          echo "-- Mounting $mnt on $CHROOT/$mnt"
          mount -o bind $mnt $CHROOT/$mnt || exit 1
     done

     if [ -f $CHROOT.shared ]
     then
          cat $CHROOT.shared | while read entry
          do
               folder=${entry%:*}
               mnt=${entry#*:}

               echo "-- Mounting $folder on $CHROOT/$mnt"
               mkdir -p $CHROOT/$mnt || exit 1
               mount -o bind $folder $CHROOT/$mnt || exit 1
          done
     fi

     echo "1" > $CHROOT.in
else
     n=`cat $CHROOT.in`
     let n=$n+1
     echo "$n" > $CHROOT.in
fi

echo "-- Entering chroot"
chroot $CHROOT /usr/bin/env HOME=/root TERM=$TERM /bin/bash --login +h || exit 1;

n=`cat $CHROOT.in`
let n=$n-1

if [ "$n" = "0" ]
then
     for umnt in /sys /proc /dev/pts /dev
     do
          echo "-- Umounting $CHROOT/$umnt"
          umount $CHROOT/$umnt || exit 1
     done

     if [ -f $CHROOT.shared ]
     then
          cat $CHROOT.shared | while read entry
          do
               mnt=${entry#*:}

               echo "-- Umounting $CHROOT/$mnt"
               umount $CHROOT/$mnt || exit 1
          done
     fi

     rm $CHROOT.in
else
     echo "$n" > $CHROOT.in
fi