Simon van der Veldt

LXC on Debian Wheezy

in virtualization, containers, lxc | feedback

LXC (LinuX Containers) offers a lot of the advantages of (para)virtualisation with the added benefits that it can run on any kind of hardware (it doesn’t need hardware support for virtualisation) with lower overhead than virtualisation. The virtual environments that LXC provides are comparable to a chroot but LXC adds control over the virtual environments resources like CPU-time and network-usage and offers more isolation. This also means it’s only possible to run the same “family” of guest operating systems as the host. I.e. it’s not possible to run Windows using LXC, but it is possible to run different Linux distributions like a Debian and Fedora guest on an Arch Linux host. Note that if you need a really secure environment LXC isn’t the right choice, stick with paravirtualisation like KVM or XEN instead.

Installing LXC

The LXC tools are included in the main Debian package repository, so installing it is very simple:

sudo apt-get install lxc

Creating a new container

Creating a new container can we done with the lxc-create command

sudo lxc-create -n containername -t templatename

You will see some feedback about the container creation on your screen including the (root) username and password you can use to login to the container once you start it.

LXC Templates

LXC template are shell scripts that automate the creation of a certain type of container. The templates can be found in /usr/share/lxc/templates/, these are the available templates in Debian Wheezy:

ls -hl /usr/share/lxc/templates/
> -rwxr-xr-x 1 0  12K Aug 22  2012 lxc-altlinux
> -rwxr-xr-x 1 0  14K Aug 22  2012 lxc-archlinux
> -rwxr-xr-x 1 0  24K Aug 22  2012 lxc-debconf
> drwxr-xr-x 2 0 4.0K May 21  2013 lxc-debconf.d
> lrwxrwxrwx 1 0   11 Aug 22  2012 lxc-debian -> lxc-debconf
> lrwxrwxrwx 1 0   13 Aug 22  2012 lxc-debian.d -> lxc-debconf.d
> -rwxr-xr-x 1 0 9.8K Aug 22  2012 lxc-fedora
> -rwxr-xr-x 1 0 9.9K Aug 22  2012 lxc-opensuse
> lrwxrwxrwx 1 0   11 Aug 22  2012 lxc-progress -> lxc-debconf
> lrwxrwxrwx 1 0   13 Aug 22  2012 lxc-progress.d -> lxc-debconf.d
> -rwxr-xr-x 1 0 4.0K Aug 22  2012 lxc-sshd
> -rwxr-xr-x 1 0 7.6K Aug 22  2012 lxc-ubuntu-cloud

To use a template simply remove lxc- from the template’s name. So to use the lxc-debian you only have to write debian as templatename.

sudo lxc-create -n containername -t debian

Overview and status of containers

To see if the container was created succesfully we use the lxc-list command. This will show all available LXC containers grouped by their status (running, frozen and stopped). Our newly created container should be listed in the stopped section.

sudo lxc-list
>RUNNING
>
>FROZEN
>
>STOPPED
> containername

Starting a container

Starting a container can be done with the lxc-start command. Note that you want to add the -d switch to make the container daemonize, if you don’t do that it will take over your current terminal session and you won’t be able to exit back to it.

sudo lxc-start -d -n containername

Now if we run lxc-list our container is show as running

sudo lxc-list
>RUNNING
> containername
>
>FROZEN
>
>STOPPED

Using a container

To actually use a container from your host we make use of the ‘lxc-console’ command.

sudo lxc-console -n containername

After doing this you will see a new terminal with a login prompt just as if you just started up a new session. You can login with the username and password that were given to you when you created the container.

That’s it, you are now inside your Debian container and you can use it just like a normal install of Debian :)