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Linux Containers (LXC) is a lightweight system virtualization that uses resource isolation instead of the hardware emulation approach used by KVM and Xen. For users who do not require full OS virtualization as provided by KVM and Xen, container technologies such as LXC provide an attractive performant solution for virtualization.

Cloudstack currently does not support containers such as LXC and OpenVZ.

Purpose

This docoument contains the design specification for LXC support in Cloudstack.

Status

Currently in development/testing, see last section below for detailsCode complete, feature has been merged to master branch.

References

• Jira: https://issues.apache.org/jira/browse/CLOUDSTACK-922^{Image Removed}
• Github: https://github.com/gilt/incubator-cloudstack^{Image Removed}
• Mail thread: http://mail-archives.apache.org/mod_mbox/incubator-cloudstack-dev/201301.mbox/%3CCAD3R0XntF759eiafbLOdvftBQUX8yER2t20wTFGvhph6sgKWgw@mail.gmail.com%3E^{Image Removed}
• Meeting Notes:
  • 2013-02-05: http://wilderness.apache.org/archives/cloudstack-meeting-05_02_2013-11006.html

Feature Specification

LXC will be implemented as a hypervisor in Cloudstack and will be a first class citizen to the other hypervisors such as Xen, KVM, VMWare. As such, a user will be able to select LXC as the hypervisor for all areas a hypervisor is selectable and where the system resources have been met.

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Each of the different hypervisors currently have their own System VMs. These system VM images are used to run a console proxy, secondary storage, and router VMs.

We will need to create a System VM for LXC. Until this is ready, we can run a second cluster with a KVM/Xen host to provide the System VM functionality.

If we didn't have the System VM for LXC, we would have to consider how to replace the 3 system VMs:

• Secondary Storage VM: Run this on the management server
• Console VM: Libvirt 1.0.0 does not support the <graphics> tag for LXC which is used for remote vnc connections.
• Router VM: Configure the Guest OS directly with network setttings

Development/testing notes

After you have your development environment setup, here are additional things to note:

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• add: hypervisor.type=lxc

discussed the possibility of creating System VMs for LXC. There was concern with the complexity and potential issues involving iptables for the router inside an LXC container. As an intermediate solution we are going to use KVM System VMs inside the LXC Cluster.

Direct Networking

Libvirt supports direct attachment of the guest VM's network to a physical interface. To enable this mode, add the following to agent.properties:

libvirt.vif.driver=com.cloud.hypervisor.kvm.resource.DirectVifDriver
network.direct.source.mode=private (other values: bridge|vepa)
network.direct.device=eth0

NOTE: The network device that is specified should not be a slave to any bridges.

Environment setup and testing

Obtaining latest code

The LXC code has been merged to the master branch for Cloudstack:

git clone https://git-wip-us.apache.org/repos/asf/cloudstack.git

Follow directions in /docs/en-US/build-rpm.xml to build RPMs for Cloudstack.

Installing Cloudstack

I will not cover how to install Cloudstack, please use the latest online documents. There are a few things to note when using the LXC code:

1. Use the latest system VM images from Jenkins

Import the latest system VM image:

• http://jenkins.cloudstack.org/view/master/job/build-systemvm-master/

/web/cloudstack/scripts/storage/secondary/cloud-install-sys-tmplt -m /mnt/secondary -u http://jenkins.cloudstack.org/view/master/job/build-systemvm-master/lastSuccessfulBuild/artifact/tools/appliance/dist/systemvmtemplate-2013-04-14-master-kvm.qcow2.bz2 -h kvm -F

2. LXC container

Cloudstack will not come bundled with an LXC container image, so you will need to prepare one yourself or download one

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