lxc-febootstrap

#!/bin/bash
# set -ex

DISTRO="fedora-13"
CACHE="/var/cache/lxc/${DISTRO}"

# Default container name
NAME="fedora"
CONFFILE="lxc.conf"
MNTFILE="mount.conf"
UTSNAME=
MTU="1500"

# These paths are within the container so do not need to obey configure prefixes
FSTAB="/etc/fstab"

################################################################################
#                    DISTRO custom configuration files
################################################################################

# custom selinux

write_distro_selinux() {
    mkdir -p ${ROOTFS}/selinux
    echo 0 > ${ROOTFS}/selinux/enforce
}

# custom fstab

write_distro_fstab() {
cat <<EOF > ${ROOTFS}/${FSTAB}
tmpfs  /dev/shm   tmpfs  defaults  0 0
none /dev/pts devpts defaults 0 0
EOF
}

# custom network configuration
write_distro_network() {
cat <<EOF > ${ROOTFS}/etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
HOSTNAME=${UTSNAME}
NM_CONTROLLED=no
TYPE=Ethernet
MTU=${MTU}
EOF
}

# custom hostname

write_distro_hostname() {
cat <<EOF > ${ROOTFS}/etc/sysconfig/network
NETWORKING=yes
HOSTNAME=${UTSNAME}
EOF
}

################################################################################
#                        lxc configuration files
################################################################################

write_lxc_configuration() {
cat <<EOF > ${CONFFILE}
lxc.utsname = ${UTSNAME}
lxc.tty = 4
lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = virbr0
lxc.network.name = eth0
lxc.network.mtu = ${MTU}
lxc.mount = ${MNTFILE}
lxc.rootfs = ${ROOTFS}
lxc.cgroup.devices.deny = a
# /dev/null and zero
lxc.cgroup.devices.allow = c 1:3 rwm
lxc.cgroup.devices.allow = c 1:5 rwm
# consoles
lxc.cgroup.devices.allow = c 5:1 rwm
lxc.cgroup.devices.allow = c 5:0 rwm
lxc.cgroup.devices.allow = c 4:0 rwm
lxc.cgroup.devices.allow = c 4:1 rwm
# /dev/{,u}random
lxc.cgroup.devices.allow = c 1:9 rwm
lxc.cgroup.devices.allow = c 1:8 rwm
# /dev/pts/* - pts namespaces are "coming soon"
lxc.cgroup.devices.allow = c 136:* rwm
lxc.cgroup.devices.allow = c 5:2 rwm
# rtc
lxc.cgroup.devices.allow = c 254:0 rwm
EOF
}

write_lxc_mounts() {
cat <<EOF > ${MNTFILE}

EOF
}

post_config_distro() {
sed -i 's|.sbin.start_udev||' ${ROOTFS}/etc/rc.sysinit
sed -i 's|.sbin.start_udev||' ${ROOTFS}/etc/rc.d/rc.sysinit
chroot ${ROOTFS} chkconfig udev-post off
chroot ${ROOTFS} chkconfig auditd off
chroot ${ROOTFS} chkconfig network on
chroot ${ROOTFS} passwd 
}

write_distro_devd() {
# taken from http://blog.bodhizazen.net/linux/lxc-configure-fedora-containers/
ROOTFSDEV="${ROOTFS}/dev"
rm -rf ${ROOTFSDEV}/
mkdir ${ROOTFSDEV}
mknod -m 666 ${ROOTFSDEV}/null c 1 3
mknod -m 666 ${ROOTFSDEV}/zero c 1 5
mknod -m 666 ${ROOTFSDEV}/random c 1 8
mknod -m 666 ${ROOTFSDEV}/urandom c 1 9
mkdir -m 755 ${ROOTFSDEV}/pts
mkdir -m 1777 ${ROOTFSDEV}/shm
mknod -m 666 ${ROOTFSDEV}/tty c 5 0
mknod -m 666 ${ROOTFSDEV}/tty0 c 4 0
mknod -m 666 ${ROOTFSDEV}/tty1 c 4 1
mknod -m 666 ${ROOTFSDEV}/tty2 c 4 2
mknod -m 666 ${ROOTFSDEV}/tty3 c 4 3
mknod -m 666 ${ROOTFSDEV}/tty4 c 4 4
mknod -m 600 ${ROOTFSDEV}/console c 5 1
mknod -m 666 ${ROOTFSDEV}/full c 1 7
mknod -m 600 ${ROOTFSDEV}/initctl p
mknod -m 666 ${ROOTFSDEV}/ptmx c 5 2

}

create() {

    # choose a container name, default is already in shell NAME variable
    echo -n "What is the name for the container ? [${NAME}] "
    read _NAME_

    if [ ! -z "${_NAME_}" ]; then
	NAME=${_NAME_}
    fi

    # choose a hostname, default is the container name
    echo -n "What hostname do you wish for this container ? [${NAME}] "
    read _UTSNAME_

    if [ ! -z "${_UTSNAME_}" ]; then
	UTSNAME=${_UTSNAME_}
    else
	UTSNAME=${NAME}
    fi

    # choose the MTU size
    echo -n "What is the MTU size ? [$MTU] "
    read _MTU_

    if [ ! -z "$_MTU_" ]; then
	MTU=$_MTU_
    fi

    # the rootfs name will be build with the container name
    ROOTFS="/var/lib/lxc/rootfs/${NAME}"

    # check if the rootfs does already exist
    if [ ! -e "${ROOTFS}" ]; then
	    mkdir -p /var/lock/subsys/
	(
	    flock -n -x 200


	    RES=$?
	    if [ "${RES}" != "0" ]; then
		echo "Cache repository is busy."
		break
	    fi

	    # check the mini distro was not already downloaded
	    echo -n "Checking cache download ..."
	    if [ ! -e "${CACHE}/rootfs" ]; then

		echo "not cached"
		echo "Bootstrapping ${DISTRO}"
                febootstrap ${DISTRO} ${CACHE}/partial

		RESULT=$?
		if [ "${RESULT}" != "0" ]; then
		    echo "Failed to download the rootfs, aborting."
		    exit 1
		fi
		mv "${CACHE}/partial" "${CACHE}/rootfs"
		echo "Download complete."
	    else
		echo "Found."
	    fi

            # make a local copy of the mini
	    echo -n "Copying rootfs ..."
            if [ ! -e "/var/lib/lxc/rootfs" ];then
               mkdir -p /var/lib/lxc/rootfs
            fi
	    cp -a ${CACHE}/rootfs ${ROOTFS} && echo "Done." || exit
	) 200> "/var/lock/subsys/lxc"
    fi

write_lxc_mounts

write_lxc_configuration

write_distro_hostname

write_distro_fstab

write_distro_network

write_distro_selinux

write_distro_devd

post_config_distro

/usr/bin/lxc-create -n ${NAME} -f ${CONFFILE}
RES=$?

# remove the configuration files
rm -f ${CONFFILE}
# rm -f ${MNTFILE}

if [ "${RES}" != "0" ]; then
    echo "Failed to create '${NAME}'"
    exit 1
fi

echo "Done."
echo -e "\nYou can run your container with the 'lxc-start -n ${NAME}'\n"
}

destroy() {

    echo -n "What is the name for the container ? [${NAME}] "
    read _NAME_

    if [ ! -z "${_NAME_}" ]; then
	NAME=${_NAME_}
    fi

    /usr/bin/lxc-destroy -n ${NAME}
    RETVAL=$?
    if [ ! ${RETVAL} -eq 0 ]; then
	echo "Failed to destroyed '${NAME}'"
	return ${RETVAL}
    fi

    ROOTFS="/var/lib/lxc/rootfs/${NAME}"

    echo -n "Shall I remove the rootfs [y/n] ? "
    read
    if [ "${REPLY}" = "y" ]; then
	rm -rf ${ROOTFS}
    fi

    return 0
}

help() {
    cat <<EOF

This script is a helper to create ${DISTRO} system containers.

The script will create the container configuration file following
the informations submitted interactively with 'lxc-${DISTRO} create'

The first creation will download, with yum, a ${DISTRO} minimal
install and store it into a cache.

The script will copy from the cache the root filesystem to the
current directory.

If there is a problem with the container, (bad configuration for
example), you can destroy the container with 'lxc-${DISTRO} destroy'
but without removing the rootfs and recreate it again with
'lxc-${DISTRO} create'.

If you want to create another ${DISTRO} container, call the 'lxc-${DISTRO}
 create' again, specifying another name and new parameters.

At any time you can purge the ${DISTRO} cache download by calling
'lxc-${DISTRO} purge'

Have fun :)

EOF
}

purge() {

    if [ ! -e ${CACHE} ]; then
	exit 0
    fi

    # lock, so we won't purge while someone is creating a repository
    (
	flock -n -x 200

	RES=$?
	if [ "${RES}" != "0" ]; then
	    echo "Cache repository is busy."
	    exit 1
	fi

	echo -n "Purging the download cache..."
	rm --preserve-root --one-file-system -rf ${CACHE} && echo "Done." || exit 1
	exit 0

    ) 200> "/var/lock/subsys/lxc"
}

# Note: assuming uid==0 is root -- might break with userns??
if [ "$(id -u)" != "0" ]; then
	echo "This script should be run as 'root'"
	exit 1
fi

# Detect which executable we were run as, lxc-fedora or lxc-redhat
CACHE="/var/cache/lxc/${DISTRO}"
mkdir -p ${CACHE}

case "$1" in
    create)
	create;;
    destroy)
	destroy;;
    help)
	help;;
    purge)
	purge;;
    *)
	echo "Usage: $0 {create|destroy|purge|help}"

esac