In this post I will demonstrate how to use debootstrap to make a root file system (rootfs) for a LXC container using Ubuntu Lucid (10.04).

Note: At the time of this post, Lucid (Ubuntu 10.04) is in the Alpha stage of development. As with all development releases, breakage may occur.

Commands in this tutorial are run as root, so to obtain a root shell use:

sudo -i

The working directory for this tutorial is /home/bodhi/lxc , so config.ubuntu and rootfs.ubuntu are both located in /home/bodhi/lxc

Make a rootfs via debootstrap

debootstrap –variant=minbase lucid rootfs.ubuntu # two – - in front of “- -variant”

Configure the container

Copy resolv.conf from host node to container

cp /etc/resolv.conf rootfs.ubuntu/etc

Fix devices in rootfs.ubuntu/dev

udev does not run in lxc containers, so you need to manually make the needed devices.

I use this script to configure the devices:

#!/bin/bash

# bodhi.zazen's lxc-config
# Makes default devices needed in lxc containers
# modified from http://lxc.teegra.net/

ROOT=$(pwd)
DEV=${ROOT}/dev
if [ $ROOT = '/' ]; then
printf "\033[22;35m\nDO NOT RUN ON THE HOST NODE\n\n"
tput sgr0
exit 1
fi
if [ ! -d $DEV ]; then
printf "\033[01;33m\nRun this script in rootfs\n\n"
tput sgr0
exit 1
fi
rm -rf ${DEV}
mkdir ${DEV}
mknod -m 666 ${DEV}/null c 1 3
mknod -m 666 ${DEV}/zero c 1 5
mknod -m 666 ${DEV}/random c 1 8
mknod -m 666 ${DEV}/urandom c 1 9
mkdir -m 755 ${DEV}/pts
mkdir -m 1777 ${DEV}/shm
mknod -m 666 ${DEV}/tty c 5 0
mknod -m 666 ${DEV}/tty0 c 4 0
mknod -m 666 ${DEV}/tty1 c 4 1
mknod -m 666 ${DEV}/tty2 c 4 2
mknod -m 666 ${DEV}/tty3 c 4 3
mknod -m 666 ${DEV}/tty4 c 4 4
mknod -m 600 ${DEV}/console c 5 1
mknod -m 666 ${DEV}/full c 1 7
mknod -m 600 ${DEV}/initctl p
mknod -m 666 ${DEV}/ptmx c 5 2

exit 0

The script is very slightly modified from This page and is saved in /usr/local/bin/lxc-config .

Make it executable :

chmod u+x /usr/local/bin/lxc-config

Run the script in rootfs.ubuntu

cd rootfs.ubuntu
/usr/local/bin/lxc-config # fix /dev

Generate a config file

I call it config.ubuntu . Make sure the following information is accurate:

container name (lxc.utsname)
network (lxc.network.ipv4)
rootfs (lxc.rootfs)

lxc.utsname = ubuntu
lxc.tty = 4
lxc.network.type = veth
lxc.network.flags = up
lxc.network.link = br0
lxc.network.name = eth0
lxc.network.mtu = 1500
lxc.network.ipv4 = 192.168.0.0/24
lxc.rootfs = /home/bodhi/lxc/rootfs.ubuntu
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

Modify the rootfs

chroot into rootfs.ubuntu and configure

chroot rootfs.ubuntu

apt-get install --force-yes -y gpgv # two - - in front of "--force-yes"
apt-get update

# set locales
apt-get install -y language-pack-en
update-locale LANG=”en_US.UTF-8″ LANGUAGE=”en_US.UTF-8″ LC_ALL=”en_US.UTF-8″

# Add to the installed applications
apt-get install -y adduser apt-utils iproute netbase nano openssh-blacklist openssh-blacklist-extra openssh-server console-setup sudo ping

#Set a root passwd
passwd

# As an alternate to setting a root password, you may of course add a new user and configure sudo.

#exit chroot
exit

Configure networking

edit rootfs.ubuntu/etc/network/interfaces

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address 192.168.0.60
netmask 255.255.255.0
broadcast 192.168.0.255
gateway 192.168.0.1

Remove tty4, 5, & 6

rm rootfs.ubuntu/etc/init/tty{4,5,6}.conf

Fix /var/run/network/ifstate

mkdir -p rootfs.ubuntu/var/run/network
touch rootfs.ubuntu/var/run/network/ifstate

Add a directory to allow ssh user privilege separation

mkdir -p rootfs.ubuntu/var/run/sshd

Edit rootfs.ubuntu/lib/init/fstab

Using any editor, open rootfs.ubuntu/lib/init/fstab and comment out the following lines:

#none /proc proc nodev,noexec,nosuid 0 0
#none /sys sysfs nodev,noexec,nosuid 0 0
#none /dev devtmpfs,tmpfs mode=0755 0 0

Edit rootfs.ubuntu/etc/init/rc-sysinit.conf

Using any editor, open rootfs.ubuntu/etc/init/rc-sysinit.conf, look for the line

start on filesystem and net-device-up IFACE=lo

and change it to

start on filesystem # and net-device-up IFACE=lo

Add an init (upstart) script

Using any editor, make a file rootfs.lucid/etc/init/lxc.conf and add:

# LXC – Fix init sequence to have LXC containers boot with upstart

# description “Fix LXC container - Lucid”

start on startup

task
pre-start script
mount -t proc proc /proc
mount -t devpts devpts /dev/pts
mount -t sysfs sys /sys
mount -t tmpfs varrun /var/run
mount -t tmpfs varlock /var/lock
mkdir -p /var/run/network
touch /var/run/utmp
chmod 664 /var/run/utmp
chown root.utmp /var/run/utmp
if [ "$(find /etc/network/ -name upstart -type f)" ]; then
chmod -x /etc/network/*/upstart || true
fi
end script

script
start networking
initctl emit filesystem --no-wait
initctl emit local-filesystems --no-wait
initctl emit virtual-filesystems --no-wait
init 2
end script

Configure and start the container

Create the container:

lxc-create -f /home/bodhi/lxc/conf.ubuntu -n ubuntu
lxc-start -n ubuntu

You should now be able to access the container with either lxc-console or ssh

ssh root@192.168.0.60

lxc-console -n ubuntu

Update: The lucid container now boots with the -d option .