3.8. Adding a New Appliance Type to the Cluster

This procedure describes how to add a new appliance type to your cluster. This is useful when you want a subset of compute nodes to have specific behavior that is different from the rest of the compute nodes. For example, if you want all the nodes in cabinet 1 to be configured differently from the rest of the compute nodes.

Before you begin, you'll want to be comfortable with the Rocks XML framework that is used to produce a configuration graph. Details on this framework are found in the Reference Guide.

First, you'll need to create a new node XML file. This file will contain the configuration scripts and/or packages that will be applied to each of your appliances. Let's call it my-compute.xml. This file should be created in the directory /home/install/site-profiles/5.0/nodes. Below is the contents of the file:

<?xml version="1.0" standalone="no"?>

<kickstart>
  
<description>
My specialized compute node
</description>

  
<changelog>
</changelog>

<post>

<file name="/etc/motd" mode="append">
My Compute Appliance
</file>

</post>

</kickstart> 

Now, we'll link the above file into the existing XML configuration graph. We'll simply point the above XML node to the existing compute.xml node. In object-oriented terms, we are inheriting all the functionality of the compute appliance and then extending it.

To link my-compute.xml to compute.xml, in the directory /home/install/site-profiles/5.0/graphs/default, create the file my-appliance.xml and have it contain:

<?xml version="1.0" standalone="no"?>

<graph>

<description>
</description>

<changelog>
</changelog>

<edge from="my-compute">
        <to>compute</to>
</edge> 

<order gen="kgen" head="TAIL">
        <tail>my-compute</tail>
</order>

</graph>

To apply the changes above to the current distribution, execute:

# cd /home/install
# rocks-dist dist

Now we need to add an entry into the Rocks MySQL database. This is accomplished with the rocks command line:

# /opt/rocks/bin/rocks add appliance my-compute membership='My Compute' \
  short-name='mc' node='my-compute'

Now let's retarget an existing compute node. We'll use insert-ethers to accomplish this task. First, ask insert-ethers to replace compute-0-0:

# insert-ethers --replace compute-0-0

This displays the screen:

Select My Compute then hit Ok. This removes compute-0-0 from the database and the next node that asks to be configured (that is, the next node that sends out a DHCP request) will be assigned the name my-compute-0-0. To see this in action, instruct compute-0-0 to reinstall itself:

# shoot-node compute-0-0

Eventually, you'll see insert-ethers report that it discovered my-compute-0-0. After the node installs, it will be configured as a my-appliance. You can login to the node by executing:

# ssh my-compute-0-0

Your custom appliance can be applied to any new node in your system by starting insert-ethers as instructed above, then by booting a new node in configuration mode (by forcing it to PXE boot or by booting the node with the Kernel/Boot Roll).