#!/bin/bash

function mount_unionfs {

# mount temporary filesystems

if [ -z "$(mount -t unionfs | grep -w /mnt/union )" ]; then


    sudo /bin/mount -t unionfs -o dirs=/mnt/cache:/=ro unionfs /mnt/union
	

fi

if [ -n "$(mount -t unionfs | grep -w /mnt/union )" ]; then

    # basic system mounts

    if [ -z "$(mount | grep -w /mnt/union/dev)" ]; then
	sudo /bin/mount --bind /dev /mnt/union/dev 2> /dev/null
    fi
    
    if [ -z "$(mount -t devpts | grep -w /mnt/union/dev/pts)" ]; then
	sudo /bin/mount -t devpts devpts /mnt/union/dev/pts 2> /dev/null
    fi

    if [ -z "$(mount -t tmpfs | grep -w /mnt/union/dev/shm)" ]; then
	sudo /bin/mount -t tmpfs shm /mnt/union/dev/shm 2> /dev/null
    fi
    
    if [ -z "$(mount -t sysfs | grep -w /mnt/union/sys)" ]; then
	sudo /bin/mount -t sysfs sysfs /mnt/union/sys 2> /dev/null
    fi
    
    if [ -z "$(mount -t proc | grep -w /mnt/union/proc)" ]; then
	sudo /bin/mount -t proc proc /mnt/union/proc 2> /dev/null
    fi

    if [ -z "$(mount | grep -w /mnt/union/tmp)" ]; then
	sudo /bin/mount --bind /tmp /mnt/union/tmp 2> /dev/null
    fi
    
    
    
else

    echo "Mount of /mnt/union failed."
    
    exit 2

fi
    
}


function umount_unionfs {


#
# unmount /tmp
#

if [ -n "$(mount | grep -w /mnt/union/tmp)" ]; then
    sudo /bin/umount /mnt/union/tmp 2> /dev/null
fi

#
# unmount /proc
#

if [ -n "$(mount -t proc | grep -w /mnt/union/proc)" ]; then
    sudo /bin/umount /mnt/union/proc 2> /dev/null
fi

#
# unmount /sys
#

if [ -n "$(mount -t sysfs | grep -w /mnt/union/sys)" ]; then
    sudo /bin/umount /mnt/union/sys 2> /dev/null
fi

#
# unmount /dev/shm
#

if [ -n "$(mount -t tmpfs | grep -w /mnt/union/dev/shm)" ]; then
    sudo /bin/umount /mnt/union/dev/shm 2> /dev/null
fi

#
# unmount /dev/pts
#

if [ -n "$(mount -t devpts | grep -w /mnt/union/dev/pts)" ]; then
    sudo /bin/umount /mnt/union/dev/pts 2> /dev/null
fi

#
# unmount /dev
#

if [ -n "$(mount | grep -w /mnt/union/dev)" ]; then    
    sudo /bin/umount /mnt/union/dev 2> /dev/null
fi



if [ -n "$(mount | grep -w /mnt/union )" ]; then  
    sudo /bin/umount /mnt/union 2> /dev/null
fi

}




mount_unionfs

# enter the chroot

sudo /usr/sbin/chroot /mnt/union /bin/su --shell /bin/bash --login $USER

# umount temporary filesystems
  
umount_unionfs