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, Ruby, and tools for network bridges must be obtained:

 # apt-get install lxc ruby1.9.1 bridge-utils

Table of Contents Ubuntu Version Information Using the XLXC Scripts xlxc-create.rb xlxc-destroy.rb Further Using XLXC lxc-execute lxc-start and lxc-console

Ubuntu Version Information

The XLXC scripts are currently updated for Ubuntu 14.04 (Trusty Tahr). Your mileage may vary if trying to use XLXC with a different version of Ubuntu. However, you can obtain a virtual machine running Ubuntu 14.04 with an XIA kernel on the page Setting up an XIA development environment.

Using the XLXC Scripts

xlxc-create.rb

The first script in this directory is xlxc-create.rb. This script is capable of creating multiple, dual-stacked (IP and XIA) containers by bind mounting key parts of the host's filesystem and instantiating ethernet bridges. To do so, you may specify the naming scheme of the containers and how many containers you would like in the following way:

 ruby xlxc-create.rb NAME START_INDEX END_INDEX [--reset] [--script]

To create just a single Linux XIA container, while running an XIA kernel execute the following command:

 # ruby xlxc-create.rb xia 1 1

This would create a single container named xia1.

To create multiple containers at once, execute a command like the following:

 # ruby xlxc-create.rb xia 1 4

This would create four containers, named xia1, xia2, xia3, and xia4.

To reset containers by re-bind mounting their filesystems and re-creating their ethernet bridges, execute a command like the following:

 # ruby xlxc-create-rb xia 1 4 --reset

This resetting is useful in situations such as when containers are created and then the host is rebooted. At that point, the bridges and bind mounts will have been deleted, so they can be reinstalled using this option.

xlxc-destroy.rb

The second script in this directory is xlxc-destroy.rb. 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 naming scheme and the indexes of the containers. For example, if there are four XIA containers (named xia1, xia2, xia3, xia4), to destroy the last three of them, use the following command:

  # ruby xlxc-destroy.rb xia 2 4

Further Using XLXC

It is recommended to use xlxc-create and xlxc-destroy in combination with lxc-execute, lxc-start, and lxc-console, which are programs built into the lxc package.

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 use those principals in their namespace by, for example, adding entries to their routing table.

lxc-execute

lxc-execute is capable of running a container on a command. For example, if the user wants to make an XIA container and add an HID, then the following commands could be used:

 # ruby xlxc-create.rb xia 1 1
 # lxc-execute -n xia1 -- sudo xip hid new xia1 && sudo xip hid add xia1 && cat

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

A more flexible way of doing this would be to create a script that the container can run. xlxc-create is equipped to be able to create a unique script for each container if "--script" is indicated in the xlxc-create command. By default, xlxc-create creates a script for each container that looks like (for a container named xia1):

run.sh

 # Add HID for this container.
 sudo xip hid new xia1
 sudo xip hid add xia1
 # Keep container running.
 cat

This executable script can then be found in the root directory of the container. From the perspective of the host, it is /var/lib/lxc/xia1/rootfs/run.sh. With this script, the commands could instead be:

 # ruby xlxc-create.rb xia 1 1 --script
 # lxc-execute -n xia1 -- ./run.sh

This way, run.sh can contain any number of commands to be executed automatically without logging-in to the container. Users are encouraged to edit the create_script function in xlxc-create to make their own container scripts.

lxc-start and lxc-console

To start and log-in to a container, lxc-start and lxc-console can be used. By default, the login information for each container generated by xlxc-create is:

login: ubuntu
password: ubuntu

You can also log-in as root, which requires no password.

There are two ways to log-in to a container. Here we assume the name of the container is xia1.

Start a container, and later log-in to it.

 # lxc-start -n xia1 --daemon
 # lxc-console -n xia1

Start a container, and immediately log-in to it.

 # lxc-start -n xia1

Once in the console of a container, one can release the terminal from the console pressing Ctrl+a q. If it's ever necessary, one can enter Ctrl+a in a container's console pressing Ctrl+a Ctrl+a.