mkdebianrfs.sh

#!/bin/bash
#
# Copyright (c) 2013 Imagination Technologies
# Author: Alex Smith <alex.smith@imgtec.com>
#
# Creates a Debian root FS using debootstrap and configures it such that it is
# usable to boot a system.
#
# This script requires a statically linked version of QEMU for the target
# architecture to be available in PATH (named qemu-<arch>-static), and
# configured via binfmt_misc to be used to execute binaries for the target
# architecture. This is needed to perform second stage configuration of the
# target system.
#
# If the host system is running a Debian-based distro, the required packages
# can be installed with:
#
#   $ apt-get install binfmt-support qemu qemu-user-static debootstrap
#
# This will install QEMU and automatically configure binfmt_misc.
#
# TODO:
#  - Make it possible to run this completely non-interactively by allowing
#    configuration such as the root password, locale, timezone, etc to be
#    specified as arguments.
#  - Command line option for serial console configuration (just sets up ttyS0
#    at 115200 for now).
#  - Option for network configuration (just configures DHCP on eth0).
#

progname="$0"

debian_packages="locales"
debian_mirror="http://ftp.uk.debian.org/debian/"
debian_path="/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin"

usage() {
    echo "Usage: ${progname} [options...] <arch> <dist> <target>"
    echo
    echo "Creates a Debian root FS from the specified <dist> (e.g. stable,"
    echo "wheezy, testing, etc.) for <arch> using debootstrap and configures"
    echo "it such that it is bootable. Unless --tar is specified (see below),"
    echo "<target> will be taken as a directory name to create the root FS in."
    echo
    echo "Options:"
    echo
    echo "  --tar                Create a tar file instead of installing to a"
    echo "                       directory. In this case, <target> specifies"
    echo "                       the name of the output file, which will be"
    echo "                       compressed based on its file extension."
    echo "  --include=<packages> Specifies a list (comma separated) of extra"
    echo "                       packages to install in the filesystem."
    echo "  --mirror=<mirror>    URL of Debian mirror to use"
    echo "                       (defaults to ${debian_mirror})."
    echo
    echo "Example:"
    echo
    echo "  ${progname} mips wheezy /mnt"
    echo "  ${progname} --tar mipsel wheezy debian-wheezy-mipsel.tar.bz2"
    echo
}

die() {
    echo "${progname}: $@" >&2
    exit 1
}

while getopts ":h-:" optchar; do
    case "${optchar}" in
    -)
        case "${OPTARG}" in
        tar)
            target_tar=1
            ;;
        include=*)
            debian_packages="${debian_packages},${OPTARG#*=}"
            ;;
        include)
            echo "${progname}: option --${OPTARG} requires an argument." >&2
            usage >&2
            exit 1
            ;;
        help)
            usage
            exit 0
            ;;
        *)
            echo "${progname}: unknown option --${OPTARG}" >&2
            usage >&2
            exit 1
            ;;
        esac
        ;;
    h)
        usage
        exit 0
        ;;
    *)
        echo "${progname}: unknown option -${OPTARG}" >&2
        usage >&2
        exit 1
        ;;
    esac
done

shift $((OPTIND-1))
if [ $# -ne 3 ]; then
    echo "${progname}: incorrect number of arguments" >&2
    usage >&2
    exit 1
fi

target_arch="$1"
[ -z "${target_arch}" ] && die "invalid argument"
target_dist="$2"
[ -z "${target_dist}" ] && die "invalid argument"

[ $UID -ne 0 ] && die "must be run as root"
[ -z "`which debootstrap`" ] && die "cannot find debootstrap"

# QEMU gets copied into /usr/bin in the target filesystem. Need to have
# binfmt_misc configured to use that path.
target_qemu=`which qemu-${target_arch}-static`
[ -z "${target_qemu}" ] && die "cannot find qemu-${target_arch}-static"
grep -Rq "/usr/bin/qemu-${target_arch}-static" /proc/sys/fs/binfmt_misc/ \
    2>/dev/null || \
        die "/usr/bin/qemu-${target_arch}-static not configured with binfmt_misc"

set -e

# If creating a tar file, install to a temporary directory.
if [ -n "${target_tar}" ]; then
    target_tar="$3"
    [ -z "${target_tar}" ] && die "invalid argument"
    tar_dir="${target_tar%.tar*}"
    [ -z "${tar_dir}" -o "${target_tar}" = "${tar_dir}" ] && \
        die "output file name is invalid"

    tmp_dir=`mktemp -d`
    target_dir="${tmp_dir}/${tar_dir}"
    mkdir "${target_dir}"
else
    target_dir=`readlink -e "$3" || true`
    [ -z "${target_dir}" ] && die "directory '$3' does not exist"
    chown root:root "${target_dir}"
fi

# Register a cleanup handler.
cleanup() {
    set +e

    umount "${target_dir}/proc" >/dev/null 2>&1
    umount "${target_dir}/sys" >/dev/null 2>&1

    if [ -n "${target_tar}" ]; then
        echo "Removing ${tmp_dir}..."
        rm -rf "${tmp_dir}"
    fi

    trap - EXIT INT TERM
}
trap "cleanup; exit 1;" INT TERM
trap "cleanup;" EXIT

echo
echo "Creating Debian ${target_dist} RFS for ${target_arch} in '${target_dir}'..."
echo

debootstrap --foreign --arch="${target_arch}" --include="${debian_packages}" \
    "${target_dist}" "${target_dir}" "${debian_mirror}"

echo
echo "Configuring packages..."
echo

cp "${target_qemu}" "${target_dir}/usr/bin/qemu-${target_arch}-static"

DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true LC_ALL=C \
    LANGUAGE=C LANG=C PATH="${debian_path}" chroot "${target_dir}" \
    /debootstrap/debootstrap --second-stage
DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true LC_ALL=C \
    LANGUAGE=C LANG=C PATH="${debian_path}" chroot "${target_dir}" \
    dpkg --configure -a

echo
echo "Configuring target system..."
echo

# Create root password.
echo "Please enter a password for the root user:"
PATH="${debian_path}" chroot "${target_dir}" passwd root

# Configure locale and time zone.
LC_ALL=C LANGUAGE=C LANG=C PATH="${debian_path}" chroot "${target_dir}" \
    dpkg-reconfigure locales
LC_ALL=C LANGUAGE=C LANG=C PATH="${debian_path}" chroot "${target_dir}" \
    dpkg-reconfigure tzdata

# Configure a serial console.
echo "T0:23:respawn:/sbin/getty -L ttyS0 115200 vt100" >> \
    "${target_dir}/etc/inittab"

# Configure a host name.
echo "debian" > "${target_dir}/etc/hostname"

# Configure networking.
echo "auto eth0" >> "${target_dir}/etc/network/interfaces"
echo "allow-hotplug eth0" >> "${target_dir}/etc/network/interfaces"
echo "iface eth0 inet dhcp" >> "${target_dir}/etc/network/interfaces"

# Configure APT.
sources_list="${target_dir}/etc/apt/sources.list"
echo "deb ${debian_mirror} ${target_dist} main" > "${sources_list}"
echo "deb-src ${debian_mirror} ${target_dist} main" >> "${sources_list}"
case "${target_dist}" in
experimental|unstable|sid)
    # No updates here.
    ;;
*)
    echo >> "${sources_list}"
    echo "deb ${debian_mirror} ${target_dist}-updates main" >> \
        "${sources_list}"
    echo "deb-src ${debian_mirror} ${target_dist}-updates main" >> \
        "${sources_list}"
    echo >> "${sources_list}"
    echo "deb http://security.debian.org/ ${target_dist}/updates main" >> \
        "${sources_list}"
    echo "deb-src http://security.debian.org/ ${target_dist}/updates main" >> \
        "${sources_list}"
    ;;
esac

# Let the user do any additional configuration.
echo
echo "Entering target system for additional configuration. Type 'exit' when done."
echo
PATH="${debian_path}" chroot "${target_dir}" /bin/bash

# Clean up.
chroot "${target_dir}" apt-get clean
rm -f "${target_dir}/usr/bin/qemu-${target_arch}-static"

echo

if [ -n "${target_tar}" ]; then
    echo "Creating ${target_tar}..."
    tar -capf "${target_tar}" -C "${tmp_dir}" "${tar_dir}"
fi

cleanup
echo "Done!"