LXC

Translation(s): none

Linux Containers (LXC) provide a Free Software virtualization system for computers running GNU/Linux. This is accomplished through kernel level isolation. It allows one to run multiple virtual units simultaneously. Those units, similar to chroots, are sufficiently isolated to guarantee the required security, but utilize available resources efficiently, as they run on the same kernel.

For all related information visit : http://lxc.sourceforge.net/

LXC is available starting with Debian 5.0 - Lenny (Kernel 2.6.26), however the LXC userspace tools are not packaged for Lenny, so they would have to be built from source. Debian 6.0 - Squeeze has full support for LXC.

LXC installs corrrectly on Wheezy, but there are some problems with the template which ships with Wheezy. Other templates can be downloaded, for more reading go to the LXC container mailing list.

You can also read some sub pages :

LXC/Squeeze-Backport

Installation

Install required packages

aptitude install lxc

Install optional packages

aptitude install bridge-utils libvirt-bin debootstrap

Prepare the host

Required: Mount cgroup reboot save (since 595964 /sys/fs/cgroup is prepared to mount cgroup, see also 601757)

Add this line to /etc/fstab

cgroup  /sys/fs/cgroup  cgroup  defaults  0   0

Try to mount it (a reboot solves an eventual "resource busy problem" in any case)

mount /sys/fs/cgroup

Optional: Enable memory cgroup support (534964) (CONFIG_CGROUP_MEM_RES_CTLR) - Since 2.6.39-bpo60-2 for Squeeze the memory cgroup support is built in, so lxc-checkconfig will give you a green result about this point. At the same time, it is deactivated by default. You need to activate memory cgroup support with a kernel parameter. When using grub2, this can be easily done by adding GRUB_CMDLINE_LINUX="cgroup_enable=memory" in /etc/default/grub and running update-grub2. Same for CONFIG_CGROUP_MEM_RES_CTLR_SWAP - see http://lists.debian.org/debian-kernel/2012/01/msg00804.html .

Check kernel configuration :

# lxc-checkconfig 
Kernel config /proc/config.gz not found, looking in other places...
Found kernel config file /boot/config-2.6.32-5-amd64
--- Namespaces ---
Namespaces: enabled
Utsname namespace: enabled
Ipc namespace: enabled
Pid namespace: enabled
User namespace: enabled
Network namespace: enabled
Multiple /dev/pts instances: enabled

--- Control groups ---
Cgroup: enabled
Cgroup namespace: enabled
Cgroup device: enabled
Cgroup sched: enabled
Cgroup cpu account: enabled
Cgroup memory controller: missing
Cgroup cpuset: enabled

--- Misc ---
Veth pair device: enabled
Macvlan: enabled
Vlan: enabled
File capabilities: enabled

Note : Before booting a new kernel, you can check its configuration
usage : CONFIG=/path/to/config /usr/bin/lxc-checkconfig

Here, I've Cgroup memory controller: missing. If you want memory control via cgroups then the Kernel recompilation is needed.

RootFS creation

Debian Squeeze

In theory you may use any tool to create a rootfs (debootstrap, multistrap, rootstock) as long as you are sure, that the result will run inside a container.
For the first time and as an example, use the provided creation script of the lxc package.

cp -a /usr/lib/lxc/templates/lxc-debian /usr/lib/lxc/templates/lxc-squeeze

(lxc-debian is designed to install lenny, which is no longer accessible from the specified archive.) Edit lxc-squeeze, replacing "lenny" with "squeeze" and "dhcp-client" with "isc-dhcp-client"

lxc-create -n myfirstcontainer -t squeeze -f /usr/share/doc/lxc/examples/lxc-veth.conf

Here, we use lxc-veth.conf config file

Debian Wheezy

lxc-create -n myfirstcontainer -t debian

This will prompt you on what distribution to install.

Setup networked containers

Create a bridge on the host (natted/routed), /SimpleBridge
VLAN + bridge setup description, see /VlanNetworking
Use libvirt package for easy network setup (/LibVirtDefaultNetwork)

Start and stop containers

To start a container and stay attached to the console run (by default, login/password is root/root) :

lxc-start -n myfirstcontainer

To start a container in the background and attached to the console at any time later run:

lxc-start -n myfirstcontainer -d
lxc-console -n myfirstcontainer

To halt a container cleanly by the containers initv-system:

lxc-halt -n myfirstcontainer

To stop a container without proper halt inside the container:

lxc-stop -n myfirstcontainer

To have containers automatically started on booting the host, edit the host's /etc/default/lxc

Support

To discuss about LXC and Debian LXC : LXC mailing list (On Gmane)

References

The repository of current main developer of LXC Debian Package
LXC Homepage
LXC on Debian Squeeze (Published on 2010-05-01)
Setting up LXC on Debian squeeze (Published on 06/11/2011)
LXC Userspace Tools
Introduction to cgroups
LXC Container based Virtualization on Debian Squeeze HowTo
How to use Linux containers (lxc) under Debian Squeeze

Known bugs and "got to know issues"

600466 - "Respawning too fast" messages due to missing tty(1234) nodes in generated container rootfs (workaround: remove from container's /etc/inittab}} or {{{mknod -m 660 dev/tty1 c 5 1 for each device)