What is LXC?

From Dwight Schauer:
“Linux Containers (LXC) are an operating system-level virtualization method for running multiple isolated server installs (containers) on a single control host. LXC does not provide a virtual machine, but rather provides a virtual environment that has its own process and network space. It is similar to a chroot, but offers much more isolation.”

Creating Virtual Environments within Virtual Machines using Red Hat Enterprise 6 or Centos 6

Why would anyone ever want to do this? Well for a number of reasons:

1. You only have access to one virtual machine but want to create multiple isolated services.

2. Have a requirement for multiple Linux OS versions but don’t want to invest in a heavyweight virtualisation solution.

3. Creating virtual multilayer services to that you wish to be deployed as a single virtual machine, think about a virtual network of machines encapsulated in a single easily deployed package that would only expose a single IP address e.g. reverse proxy, tomcat java container, database, and internal virtual networks).

4. Creation of lightweight development environment.

It so works on KVM, Virtualbox as well as VMware Vsphere.

LXC Setup

LXC needs kernel namespaces which is fully supported in 2.6.26 kernels and above which are currently upstream of Red Hat Enterprise Linux 5 so I opted to go to RHEL6 so I wouldn’t have to roll and maintain my own kernel (CentOS 6 wasn’t out when I tried this but it should just work).
For Red Hat Enterprise Linux 6 you will also need the RHN Optional Channel enabled so you can get ruby-selinux.

So let proceed onto how to get, compile and install LXC:

If your using DHCP on your network you can easily setup network bridging by doing the following:

And voila! LXC is now configured and ready for use, now all you need to do is install a LXC container.
Hint: I typically create a dedicated LVM Volume Group and Logical Volume for each LXC container and mount them under /srv/lxc/ e.g. /src/lxc/myvirtualbox in order to prevent it spilling over into the hosts file system and impacting other services.
You need to already have or create a lxc template here’s a link on how you can create one based on Centos 5.

Here’s some additional stuff I do: Chroot into the template and disable Bluetooth

Delete the ssh *key and *.pub from /etc/ssh

Remove the HWADDR setting in the /etc/sysconfig/network-scripts/ifcfg-eth0

Ensure that tty’s 1-4 are not commented out in /etc/inittab from each image before packaging the template up.

After that’s done and you have your template on your LXC host and are ready to deploy it.

Paste the following into the file (adjust as necessary):

Save the file and create a new fstab file

Paste in the following data and edit as necessary

Now you can create myvirtualbox lxc container by typing in

And fire it up and a console to go with it using screen:

You can now use the following command to see the init boot session

To see and interact with the console.