XIA Linux Containers (XLXC)

It is useful to create many XIA hosts for debugging and testing purposes. Although virtual machines can be created to suit this need, simulating larger networks of dozens or hundreds of nodes requires a more lightweight virtualization solution. Linux Containers are perfect for this task, as they isolate system resources and namespaces to create virtual environments and do not require as many resources as true virtual machines do.

There is a repository that contains scripts for creating many containers that have the ability to run the XIA kernel, assuming the host machine is running XIA. These scripts can be obtained with this command:

 $ git clone http://github.com/cjdoucette/xlxc.git

Before the scripts can be used, the basic LXC package and Ruby must be obtained:

 # apt-get install lxc ruby1.9.1

Using the XLXC Scripts

The first script in this directory is xlxc-create. This script is capable of creating multiple XIA or IP containers, which are always of the form "stacki" where "stack" is either "xia" or "ip" and "i" is the number container of that stack. To create just a single Linux XIA container, while running an XIA kernel execute the following command:

 # ruby xlxc-create.rb

To create multiple containers at once, the --count option can be used:

  # ruby xlxc-create.rb --count=4

To create containers without XIA tools installed, use the --ip option:

  # ruby xlxc-create.rb --count=2 --ip

The second script in this directory is xlxc-destroy. The purpose of this script is to stop and destroy any containers specified, including any files that were bind mounted. To do this, the user needs to specify the name of the containers to be destroyed by listing the name of the relevant network stack and the indexes of the containers. For example, if there are four XIA containers (named xia1, xia2, xia3, xia4), to destroy the last two of them, use the following command:

  # ruby xlxc-destroy.rb xia 3 4

Further Using XLXC

It is recommended to use xlxc-create and xlxc-destroy in combination with lxc-execute, which is capable of running a given container on a command. For example, if the user wants to make an XIA container add an HID, then the following commands could be used:

 # ruby xlxc-create.rb
 # lxc-execute -n xia1 -- sudo xip hid new xia1 && sudo xip hid add xia1 && yes > /dev/null

This would create an XIA container, create a new HID, and add that HID to the container. The final command, yes > /dev/null, is a way of keeping the container running. Otherwise, the container will close.

An even more useful way of doing this would be to create a script that the container can run. For example, a Ruby script for the container to run may look like:

container.rb

 # Add HIDs to start NWP.
 `sudo xip hid new xia1`
 `sudo xip hid add xia1`
 # Keep container running.
 yes > /dev/null

Then, the script must either be bind mounted to the container or copied into the container. From the perspective of the host, the root filesystem for a container named "xia1" is usually found in /var/lib/lxc/xia1/rootfs (on Ubuntu, at least). With the script in place, the commands could instead be:

 # ruby xlxc-create.rb
 # lxc-execute -n xia1 -- ruby container.rb

Of course, this would require installing, bind mounting, or copying the ruby application into the container as well. However, now container.rb could contain any number of commands that the container would execute.

Note: Containers share the kernel with the host. Therefore, a container cannot add or remove kernel modules. In order to use XIA, the host must first load any principals that are desired. However, containers are then free to freely use those principals in their namespace, for example, adding entries to their routing table.

Note: In order to use lxc-execute, each container must also have LXC installed, bind mounted, or copied into it. In xlxc-create there is an example of how to bind mount the relevant LXC files from the host to a container, but depending on your version of Ubuntu and LXC your mileage may vary.