When you clone a VM you have the option of selecting Guest Customization if you have it configured correctly. In order to understand why you should use the Guest Customization Specification, you must first understand what it does:

• Windows
  • Configure the Windows Registration Information
  • Configure the unique Windows Computer Name
  • Configure the Administrator password
  • Configure the IP, DNS, WINS and other network configuration settings
  • Join a newly created virtual machine to the Windows Domain of choice
  • Configure the Windows virtual machine to obtain a new unique Windows Security Identifier (SID)
  • Configure the Windows Product Key
  • Configure the desired Time Zone
  • Configure any custom scripts to be run upon first time login
• Linux
  • Configure the unique Linux Computer Name
  • Configure the IP, DNS and other network configuration settings

With this information, you can begin to see the importance of the Guest Customization Specification. Without it, you run the risk of having:

• Duplicate IP addresses on the network
• Duplicate hostnames on the network
• Permission problems with files and directories (Windows only)

In addition, the Guest Customization Specification automates a lot of processes that would otherwise need to be manually completed after cloning a new system. This includes:

• Licensing
• Logging into the new system for the first time
• Joining a domain
• Running one-time scripts

Expect to see more posts about Guest Customization Specification in the future!

Another interesting VMware issue came up this week. I was in the process of reconfiguring some ESX hosts and as such was forced to put these hosts in maintenance mode. As it turns out, one VM was located on the local storage of an ESX host and as such, I attempted to perform a Storage vMotion so the maintenance mode request would be successful. After about 20% completion, vCenter Server displayed the following error message, "The virtual disk is either corrupted or not a supported format."

How do you troubleshoot this problem?

In my last blog entry about cloud computing, I answered the question: what is cloud computing? To do this, I defined the term cloud and then laid out some fundamental characteristics of cloud computing. Now, I would like to give a more formal definition of cloud computing. In perusing multiple articles on the topic, it has become apparent to me that there is no globally accepted definition of the term. This is understandable given the fact that cloud computing is still an evolving paradigm. In addition, many definitions that are available lack core and fundamental characteristics of the term.

In my last blog entry, I spoke about the importance of restarting management services when troubleshooting VMware ESX issues. One thing that I have noticed is that if you SSH to an ESX host and restart the management services you cannot cleanly exit out from the SSH session. To illustrate this point, SSH to a non-production ESX host and run the following commands:

[root@esx01] # service mgmt-vmware restart
Stopping VMware ESX Server Management services:



VMware ESX Server Host Agent Watchdog
[  OK  ]


VMware ESX Server Host Agent
[  OK  ]


Starting VMware ESX Server Management services:



VMware ESX Server Host Agent (background)
[  OK  ]


Availability report startup (background)
[  OK  ]


[root@esx01] # service vmware-vpxa restart



Stopping vmware-vpxa:
[  OK  ]


Starting vmware-vpxa:
[  OK  ]


[root@esx01] # exit
logout

You will notice the management services restart successfully, but your terminal hangs when trying to exit. What causes this and how can you fix it?

There are two VMware ESX commands that every VMware ESX administrator should know and master:

• service mgmt-vmware restart
• service vmware-vpxa restart

You may notice that for almost every VMware problem I blog about, the first step in troubleshooting is almost always restarting the management services. The reason for this is simple, it is the quickest and easiest way to fix a majority of the ESX problems experienced. I would compare it to restarting Windows in order to fix a Windows OS problem.

So what do these two services actually do?