The right way to maintain build grid for continuous integration is virtualization.

Cruise team use cruise to do continuous integration.
We are using virtual machines of Xen server to setup our CI build grid, rather than physical machines. Because the virtual machines are easy to maintain. You can easily import a VM to jion the build grid. Only one thing which you have to do is to change the host name of the new VM. The backup of original virtual machine has setup with cruise agent and the environment our continuous integration need.
 
The issue of disk space raised over time.

Due to the low disk space in the original virtual machine's backup, the agents often run out of disk space when we add multiple pipelines for release management.

So we have to figure out how to add more disk space under /var/lib/cruise-agents/pipelines.

What I did was to add a new partition to the VM and backup the new VM as the seed.

It was really easy. I like VMs.

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how to add a hard driver to linux and mount it.

1. sudo rm -rf /var/lib/cruise-agent/pipelines
2. sudo /sbin/fdisk /dev/xvdc
3. and the prompt: n (create a new empty dos partition table) and: w
4. sudo mkfs -t ext3 /dev/xvdc
5. sudo mkdir /var/lib/cruise-agent/pipelines
6. sudo mount -t ext3 /dev/xvdc /var/lib/cruise-agent/pipelines 
7. sudo chown -R cruise:cruise /var/lib/cruise-agent/pipelines