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Quick Tip - How to snapshot & revert a physical ESXi host

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Nested environment, which is something I did quite a bit of as a customer and still continue to do so today. I could easily snapshot my Nested ESXi environment, perform my tests and then quickly rollback to my original starting state. However, when it comes to testing a physical ESXi host, it is a bit more challenging as there is no "quick" snapshot functionality as far as I was aware of. It was only until recently did I have a use case for this and picked up a nice tidbit from one of our engineers on the team. It turns out you could "snapshot" a physical or even virtual ESXi host by just backing up the state.tgz file and then restoring it. As the name suggest, the state.tgz file contains all the configurations of your ESXi host. The process is pretty straight forward:

  1. SCP /bootbank/state.tgz and back that up to your local system or shared storage
  2. Perform your tests or make changes to the system
  3. When you are ready to restore, copy the state.tgz back into /bootbank folder
  4. Login to ESXi Shell and run reboot -f which will ensure no changes are saved to our state.tgz

Once the ESXi host reboots, it will use the restored state.tgz file and your system will be back at its original state. This process is actually not new, ESXi already provides a way to backup/restore

Automating the Search for Lopsided Bootbanks in ESXi 4.x

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I read an interesting article this weekend about lopsided bootbanks in ESXi and as Kyle states, the impact of this is very minor. If you would like to check to see if you would be impacted by this and remediate prior to upgrading from ESXi 4.x to 5.x, you can use the following vSphere SDK for Perl script findLopsidedBootbanks.pl which was modified from an existing script (queryDiskParition.pl) that allows you to query for partitions on a disk.

Note: Remediation is only necessary if you plan on using VUM (Update Manager) to upgrade from ESXi 3.x/4.x to 5.x as it expects both bootbanks to be the same size, else a scripted install/upgrade will extend bootbank1 and ensure it matches bootbank2 size. 

Here is an ESXi 3.5 host that was directly upgraded to ESXi 4.0 and as you can see from the partition layout, bootbank1 (partition 5) and bootbank2 (partition 6) differ in size.

Using the findLopsidedBootbanks.pl you can connect to either vCenter server or directly to an ESXi host and it will check to see if there are any lopsided bootbanks.

Download: findLopsidedBootbanks.pl script here.