ubuntu-defaults-chroot

#!/bin/sh
# Automatic chrooting in a ubuntu-defaults-image tree
#
# Authors: Paolo Sammicheli <xdatap1@ubuntu.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

set -e

# Decomment for enabling debug
# set -x

help () {
    cat >&2 <<EOF
Usage: $0 [--help]

It sets up a proper chroot enviroment, start it and clean it after the operations. 

It must be invoked from a directory containing files made with 
ubuntu-default-image. More infos: https://wiki.ubuntu.com/ItalianCD/Tools

Options:
  --help                  : shown this help
EOF
}

chroot_file () {

$SUDO cat <<EOF > ./start-chroot
#!/bin/sh
echo "setting up chroot enviroment..."
mount none -t proc /proc
mount none -t sysfs /sys
mount none -t devpts /dev/pts
export HOME=/root
export LC_ALL=C

bash

echo "cleaning up chroot enviroment..."
apt-get clean
rm -rf /tmp/*
> /etc/resolv.conf
> /etc/hosts
umount -lf /proc
umount -lf /sys
umount -lf /dev/pts
exit
EOF

}

jump_in () {
# checking if exist .stage directory, otherwise exit with error

if [ ! -d .stage -o ! -d chroot ]; then
	echo "\nERROR: .stage or chroot directories not found. \nYou must run this sommand from a directory containing files mage with ubuntu-defaults-image"
else
    echo "setting up enviroment"
    $SUDO cp /etc/hosts chroot/etc/
    $SUDO cp /etc/resolv.conf chroot/etc/resolv.conf

    # Creating the chrooted start script
    chroot_file
    $SUDO mv start-chroot chroot/usr/bin/
    $SUDO chmod +x chroot/usr/bin/start-chroot
    
    # starting the chroot enviroment
    echo "entering in the chroot enviroment. Use \"exit\" for ending the session"
    $SUDO chroot chroot usr/bin/start-chroot
    
    # deleting chrooted start script
    echo "performing cleaning..."
    $SUDO rm chroot/usr/bin/start-chroot
fi
}

#####################
# Starting main body

# Checking sudo
if [ "$(id -u)" = 0 ]; then
    SUDO=env
else
    SUDO=sudo
fi

# Checking parameters. If so printing help
if [ -z $1 ]; then
	jump_in
else
	help
fi