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

$CHROOT.shared contains shared folder to be binded in the chroot :

/home/linkdd/Documents:/mnt/shared/Documents

This will mount /home/linkdd/Documents on $CHROOT/mnt/shared/Documents, if the directory doesn't exist, it will be created.

$CHROOT.in contains the number of user currently in the chroot, when the first user enter into it, all filesystems are mounted, and when the last leaves the chroot, all filesystems are umounted

How to use this script (assuming I have saved above file in ~/enter-chroot.bash) ?

Wow, I was not expecting someone to use a script that old ( so old I didn't remember writing it :D ).

This will do the trick:

$ sudo bash /path/to/enter-chroot.bash /path/to/my/chroot

And you can create a file /path/to/my/chroot.shared to mount specific folders inside it (see my comment above).