Script to generate LXC containers for EC2

lxc-ubuntu.sh

#!/bin/bash

#
# Template script for generating ubuntu container for LXC with the same
# ubuntu relase as the host
#
# This script is based on lxc-debian for EC2 (Daniil Kulchenko <[email protected]>)
# wich itself is based on lxc-debian         (Daniel Lezcano <[email protected]>)
#

# Copyright © 2010 Wilhelm Meier
# Author: Wilhelm Meier <[email protected]>
#
# With bugfixes and modifications for EC2 support by 
# Daniil Kulchenko ([email protected]), Copyright ¬© 2011.
#
# With ubunutu-release-autodetect by
# Michael Contento ([email protected]), Copyright ¬© 2011.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2, as
# published by the Free Software Foundation.

# 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, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#

get_ubuntu_release() 
{
    lsb_release --codename --short
}

configure_ubuntu()
{
    rootfs=$1
    hostname=$2

    # configure the network using the dhcp
    cat <<EOF > $rootfs/etc/network/interfaces
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp
EOF

    if [ -e $rootfs/etc/dhcp/dhclient.conf ]; then
        sed -i "s/<hostname>/$hostname/" $rootfs/etc/dhcp/dhclient.conf
    elif [ -e $rootfs/etc/dhcp3/dhclient.conf ]; then
        sed -i "s/<hostname>/$hostname/" $rootfs/etc/dhcp3/dhclient.conf
    fi

    # set the hostname
    cat <<EOF > $rootfs/etc/hostname
$hostname
EOF
    # set minimal hosts
    cat <<EOF > $rootfs/etc/hosts
127.0.0.1 localhost $hostname
EOF

    cp $rootfs/etc/init/tty1.conf $rootfs/etc/init/console.conf
    rm $rootfs/etc/init/tty*
    sed -i 's/tty1/console/' $rootfs/etc/init/console.conf

    echo

    echo "Please change the root password! (currently, the password for root is root)"
    echo "root:root" | chroot $rootfs chpasswd

    return 0
}

download_ubuntu()
{
    packages=dialog,apt,apt-utils,resolvconf,iproute,inetutils-ping,vim,dhcp3-client,ssh,lsb-release,lxcguest

    cache=$1
    arch=$2
    release=$(get_ubuntu_release)

    # check the mini ubuntu was not already downloaded
    mkdir -p "$cache/partial-$arch"
    if [ $? -ne 0 ]; then
        echo "Failed to create '$cache/partial-$arch' directory"
        return 1
    fi

    # download a mini ubuntu into a cache
    echo "Downloading ubuntu minimal ..."
    debootstrap --verbose --variant=minbase --components=main,universe --arch=$arch --include=$packages $release $cache/partial-$arch 
  
    if [ $? -ne 0 ]; then
        echo "Failed to download the rootfs, aborting."
        return 1
    fi

    mv "$1/partial-$arch" "$1/rootfs-$arch"
    echo "Download complete."

    return 0
}

copy_ubuntu()
{
    cache=$1
    arch=$2
    rootfs=$3

    # make a local copy of the miniubuntu
    echo -n "Copying rootfs to $rootfs ..."
    rm -rf $rootfs
    cp -a $cache/rootfs-$arch $rootfs || return 1
    return 0
}

install_ubuntu()
{
    release=$(get_ubuntu_release)
    cache="/var/cache/lxc/$release"
    rootfs=$1
    mkdir -p /var/lock/subsys/

    (
        flock -n -x 200
        if [ $? -ne 0 ]; then
            echo "Cache repository is busy."
            return 1
        fi

        arch=$(arch)
        if [ "$arch" == "x86_64" ]; then
            arch=amd64
        elif [ "$arch" == "i686" ]; then
            arch=i386
        fi

        echo "Checking cache download in $cache/rootfs-$arch ... "
        if [ ! -e "$cache/rootfs-$arch" ]; then
            download_ubuntu $cache $arch
            if [ $? -ne 0 ]; then
                echo "Failed to download 'ubuntu base'"
                return 1
            fi
        fi

        echo "Copy $cache/rootfs-$arch to $rootfs ... "
        copy_ubuntu $cache $arch $rootfs
        if [ $? -ne 0 ]; then
            echo "Failed to copy rootfs"
            return 1
        fi

        return 0
    ) 200>/var/lock/subsys/lxc

    return $?
}

copy_configuration()
{
    path=$1
    rootfs=$2
    name=$3

    cat <<EOF >> $path/config
lxc.utsname = $name

lxc.tty = 4
lxc.pts = 1024
lxc.rootfs = $rootfs
lxc.mount  = $path/fstab

lxc.network.type = veth
lxc.network.flags = up
lxc.network.name = eth0
lxc.network.link = br0
lxc.network.ipv4 = 0.0.0.0

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
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

    cat <<EOF > $path/fstab
proc            $rootfs/proc         proc    nodev,noexec,nosuid 0 0
devpts          $rootfs/dev/pts      devpts defaults 0 0
sysfs           $rootfs/sys          sysfs defaults  0 0
EOF

    if [ $? -ne 0 ]; then
        echo "Failed to add configuration"
        return 1
    fi

    return 0
}

clean()
{
    release=$(get_ubuntu_release)
    cache="/var/cache/lxc/$release"

    if [ ! -e $cache ]; then
        exit 0
    fi

    # lock, so we won't purge while someone is creating a repository
    (
        flock -n -x 200
        if [ $? != 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
}

usage()
{
    cat <<EOF
$1 -h|--help -p|--path=<path> --clean
EOF
    return 0
}

options=$(getopt -o hp:n:c -l help,path:,name:,clean -- "$@")
if [ $? -ne 0 ]; then
    usage $(basename $0)
    exit 1
fi
eval set -- "$options"

while true
do
    case "$1" in
	-h|--help)  usage $0 && exit 0;;
	-p|--path)  path=$2; shift 2;;
	-n|--name)  name=$2; shift 2;;
	-c|--clean) clean=$2; shift 2;;
	--)         shift 1; break ;;
    *)          break ;;
    esac
done

if [ ! -z "$clean" -a -z "$path" ]; then
    clean || exit 1
    exit 0
fi

type debootstrap
if [ $? -ne 0 ]; then
    echo "'debootstrap' command is missing"
    exit 1
fi

if [ -z "$path" ]; then
    echo "'path' parameter is required"
    exit 1
fi

if [ "$(id -u)" != "0" ]; then
    echo "This script should be run as 'root'"
    exit 1
fi

mkdir -p $path

rootfs=$path/rootfs

install_ubuntu $rootfs
if [ $? -ne 0 ]; then
    echo "failed to install ubuntu"
    exit 1
fi

configure_ubuntu $rootfs $name
if [ $? -ne 0 ]; then
    echo "failed to configure ubuntu for a container"
    exit 1
fi

copy_configuration $path $rootfs $name
if [ $? -ne 0 ]; then
    echo "failed to write configuration file"
    exit 1
fi

lxc-create -n $name -f $path/config

if [ ! -z $clean ]; then
    clean || exit 1
    exit 0
fi