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5.1.3 Managing multiple operating system images
xCAT supports the creation and installation of diskfull or diskless images on the nodes. The
operating system (OS) images are built and retained on the management node. Each node
runs its own osimage definition that is tailored to the functionality they perform. The nodes
also include their own specific security hardening needs. xCAT also ensures that the node
uses a minimal osimage definition without any unnecessary file sets and applications. The
ability to rapidly reinstall the original image to the node helps protect against malicious
software.
Types of nodes for diskfull and diskless
This section describes the types of nodes that are used for diskfull and diskless.
Diskfull node
For AIX systems, this node has local disk storage that is used for the OS (a stand-alone
node). Diskfull AIX nodes often are installed by using the NIM
methods.
Diskless node
The OS is not stored on local disk. For AIX systems, this configuration means that the file
systems are mounted from a NIM server. An AIX diskless image is essentially a SPOT. This
image provides a /usr file system for diskless nodes and a root directory the contents of
which are used for the initial diskless nodes root directory. The image also provides network
boot support.
You use diskless nodes as
NIM root resource. If you want a stateless node, you must use an NIM shared_root resource.
Stateful node
A stateful node is a node that maintains its state after it is shut down and rebooted. The node
state is any node-specific information that is configured on the node. For AIX diskless nodes,
this state means that each node has its own NIM root resource that is used to store
node-specific information. Each node mounts its own root directory and preserves its state in
individually mounted root file systems. When the node is shut down and rebooted, any
information that is written to a root file system is available
Stateless node
A stateless node is a node that does not maintain its state after it is shut down and rebooted.
For AIX diskless nodes, this state means that all of the nodes use the same NIM shared_root
resource. Each node mounts the same root directory. Anything that is written to the local root
directory is redirected to memory and is lost when the node is shut down. Node-specific
information must be re-established when the node is booted.
The advantage of stateless nodes is that there is much less network traffic and fewer
resources used. which is especially important in a large cluster environment.
AIX
This section describes basic steps for updating and validating a diskfull node and a diskless
node.
For more information about updating software on AIX stand-alone (diskfull) nodes, and
updating software for AIX diskless nodes, see this website:
http://sourceforge.net/apps/mediawiki/xcat/index.php?title=Updating_AIX_Softwar
e_on_xCAT_Nodes
268
IBM Power Systems 775 for AIX and Linux HPC Solution
stateful
stateless
or
. If you want a stateful node, you must use an
rte
mksysb
or
installation
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