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lxc-debootstrap

This tool is not maintained anymore. Starting with Debian Jessie, the standard lxc-create command should be prefered.

Simple tool for creating Debian LXC containers.

It performs the following operations :

  • Creates LVM logical volume and filesystem for the container
  • Adds entry to /etc/fstab and mounts container's filesystem
  • Installs Debian using debootstrap (with cache to speed up the process)
  • Configures networking inside container
  • Disables a set of harmful/unused features for a container
  • Allows host SSH key to connect to the container's root account
  • Creates LXC configuration file
  • Configures host to launch container at boot
  • Starts the container

Requirements

Operating system

The LXC host should run Debian 7.0. Other Debian releases can work but are not currently tested.

The /sys/fs/cgroup filesystem should be mounted in /etc/fstab :

cgroup  /sys/fs/cgroup  cgroup  defaults  0   0

Following packages should be installed :

bridge-utils
debootstrap
libcap2-bin
libpam-cap
libwww-perl
lsb-release
lxc

Optionally, a SSH key can be generated for the root account, allowing to connect to new containers.

Storage

LVM volume group with enough capacity to store the containers.

Networking

A linux bridge interface whose IP address serves as network gateway for the containers. IP forwarding should be enabled.

Example entry in /etc/network/interfaces :

auto br0
iface br0 inet static
    bridge_ports eth0
    bridge_stp off
    bridge_fd 0
    bridge_maxwait 0

Quickstart

Get the lxc-debootstrap script.

Create configuration directories :

mkdir -p /etc/lxc-debootstrap/containers

Overwrite global variables in /etc/lxc-debootstrap/config if necessary. See Configuration section below for a full list.

Example (/etc/lxc-debootstrap/config) :

DEBIAN_SUITE="wheezy"
LXC_PATH="/var/lib/lxc"
LXC_VG_NAME="vg1"
BRIDGE_INTERFACE="br0"
NETMASK="255.255.255.0"
GATEWAY="10.42.0.254"
DOMAIN="example.com"

Create container-specific configuration file for an example container example1.

Example (/etc/lxc-debootstrap/containers/example1) :

IPADDR=10.42.0.29
HWADDR=42:00:00:00:00:29
DISKSIZE=5G

As root, execute lxc-debootstrap :

# ./lxc-debootstrap example1

Container parameters
--------------------
lxc_name             example1
debian_suite         wheezy
debian_arch          amd64
lvm_disksize         5G
lvm_volpath          /dev/mapper/lxc-example1
net_ipaddr           10.42.0.29
net_gateway          10.42.0.254
net_hwaddr           42:00:00:00:00:29
lxc_rootfs           /var/lib/lxc/example1/rootfs
lxc_config           /var/lib/lxc/example1/config

Create ? y

debootstrap cache dir already exists
creating logical volume /dev/mapper/lxc-example1
creating filesystem on /dev/mapper/lxc-example1
creating root directory /var/lib/lxc/example1
adding entry in /etc/fstab
mount /dev/mapper/lxc-example1 on /var/lib/lxc/example1 using fstab
populating /var/lib/lxc/example1/rootfs
networking : setting hostname
networking : setting DNS resolver
networking : setting IP configuration
networking : creating hosts file
disabling useless tty
remove pointless services in a container
disabling root password
adding SSH keys
setting APT configuration
updating packages
creating configuration file /var/lib/lxc/example1/config
starting container with lxc-start
Done.

Now, connect to the container using SSH :

# ssh 10.42.0.29
The authenticity of host '10.42.0.29 (10.42.0.29)' can't be established.
RSA key fingerprint is 35:1a:b5:4e:32:c5:0d:4b:34:b1:fe:05:45:b8:30:3a.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '10.42.0.29' (RSA) to the list of known hosts.
Linux example1 2.6.32-5-amd64 #1 SMP Sun Sep 23 10:07:46 UTC 2012 x86_64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
-bash: warning: setlocale: LC_ALL: cannot change locale (en_US.utf8)
root@example1:~#

Configuration

Main configuration file is /etc/lxc-deboostrap/config. Per-container configuration files are /etc/lxc-deboostrap/containers/CONTAINER_NAME.

They overwrite default values (see table below).

Configuration file format is shell script (directly sourced during script initialization). Variables are defined with KEY=VALUE pairs. Lines can be commented using # at the beggining of lines.

Each container MUST have these variables defined :

  • DISKSIZE
  • IPADDR
  • HWADDR

Here is a description of all configuration variables :

Variable Description
DISKSIZE Container's disk size (e.g. 5G or 1T)
IPADDR Container's IP address (e.g. 10.42.0.1)
HWADDR Container's MAC address (e.g. 42:00:00:00:00:29)
LXC_VG_NAME LVM volume group where container's logical volume are allocated
LXC_PATH LXC root path where container's mount point are created
DEBIAN_MIRROR Debian mirror URL
DEBIAN_SUITE Debian distribution codename
DEBIAN_ARCH Debian architecture
DOMAIN Domain name, used in /etc/hosts and /etc/resolv.conf if defined
NETMASK Network mask of container's network interface
GATEWAY Network gateway of container's network interface
BRIDGE_IF Network bridge interface name on host system
DNS_RESOLVER Name server IP address
SSH_PUBFILE SSH public key to allow to connect to the container root account
SSH_FROM_ADDR IP address from where SSH root login is allowed
CACHE_ROOT Directory where debootstrap cache is stored
FSTYPE Container's filesystem type

And their default values :

Variable Default value
DISKSIZE Mandatory, no default value
IPADDR Mandatory, no default value
HWADDR Mandatory, no default value
LXC_VG_NAME lxc
LXC_PATH /var/lib/lxc
DEBIAN_MIRROR http://ftp.debian.org/debian/
DEBIAN_SUITE Same as host (e.g. squeeze or wheezy)
DEBIAN_ARCH Same as host (e.g. amd64 or i386)
DOMAIN None
NETMASK 255.255.255.0
GATEWAY 10.42.0.254
BRIDGE_IF br0
DNS_RESOLVER 10.42.0.254
SSH_PUBFILE /root/.ssh/id_rsa.pub
SSH_FROM_ADDR Same as GATEWAY
CACHE_ROOT /var/cache/lxc-debootstrap
FSTYPE ext4

FAQ

Q : Can I install additional packages using deboostrap --include option ?

A : No, it could break the debootstrap cache

Author

Copyright 2013 Thomas Martin thomas@oopss.org

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/.

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Simple tool to create Debian LXC containers

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