Accessing a HMC through a SSH tunnel

For sysadmins this might be a rather easy task, but as a HMC end-user I had to search a little bit.
If you never used an IBM server you might be wondering what is an HMC. At first it seems like a notebook in a blade format as you can see on the picture below:

HMC (source: http://www.fz-juelich.de/jsc/index.php?index=1979)

But apart from its similarity to a fancy notebook, its purpose is to allow administration of IBM LPARs (or DLPARs after Power6 arrival).
There you can boot, shutdown, change CPUs and memory for LPARs, etc.
Apart from allowing the administration in loco, it provides a Java based application that can be installed either through a Java Web Start launcher or using an MSI installer.
I’ll try to explain the steps involved in running it using the JNLP Java Web Start launcher.

Setup SSH tunnel and Download JNLP

Open the SSH connection between you and any host on the same network as your HMC (this can even be the HMC itself) and tunnel the following ports from your machine to HMC’s IP.

• 30000 up to 30009
• 9090
• 9960
• 8443
• 443
• 80

Sincerely, I did not check if, strictly speaking, all the ports are necessary but feel free to test them and leave  a comment. These ports were the result of a few searches over the internet.

After setting up the tunnel, point your preferred browser to http://localhost and download the JNLP file at the following link:

HMC html page

I had to edit the codebase property of the JNLP file, but I guess it wont be necessary as I still had to edit the hosts file and add an alias for the machine name (eg.: hmc.my-server.mylocalnetwork).  You’ll end up having codebase as follows:

codebase="http://127.0.0.1/wsmship/codebase"

Edit hosts file

The next step is to edit your hosts file so it will have an extra alias pointing to 127.0.0.1. Copy the host name from the original value of the codebase property.
Then launch the JNLP file with Java Web Start. If you have the mime type correctly associated at your operating system, double click the file and wait for its launch. Sometimes it may complain at the first connection attempt, retry it and it’ll connect successfully. I guess I might still be missing some ports from the 30000~30009 range, since my first attempt was using ports from 30001~30009 and it always complained at the first attempt.

WebSphere Concepts: Cell, Node, Cluster, Server…

Quick post… If you are not familiar with WebSphere at first you might get confused with its concepts: cell, deployment manager, node, node agent, cluster, server, …

First of all, lets start with the concept of a Cell:

A Cell is a virtual unit that is built of a Deployment Manager and one or more nodes. I guess a picture will help making things clearer:

WebSphere Cell

But still there are a few concepts that need to be explained. The next obvious one is the Deployment Manager.

The Deployment Manager is a process (in fact it is an special WebSphere instance) responsible for managing the installation and maintenance of Applications, Connection Pools and other resources related to a J2EE environment. It is also responsible for centralizing user repositories for application and also for WebSphere authentication and authorization.

The Deployment Manager communicates with the Nodes through another special WebSphere process, the Node Agent.

The Node is another virtual unit that is built of a Node Agent and one or more Server instances.

The Node Agent it the process responsible for spawning and killing server processes and also responsible for configuration synchronization between the Deployment Manager and the Node. Extra care must be taken when changing security configurations for the cell, since communication between Deployment Manager and Node Agent is ciphered and secured when security is enabled, Node Agent needs to have configuration fully resynchronized when impacting changes are made to Cell security configuration.

Servers are regular Java process responsible for serving J2EE requests (eg.: serving JSP/JSF pages, serving EJB calls, consuming JMS queues, etc).

And to finish, Clusters are also virtual units that groups Servers so resources added to the Cluster are propagated to every Server that makes up the cluster, this will in fact affect usually more than a single Node instance.

Lets finish this post with another diagram to illustrate all those concepts.

WebSphere Concepts