Check this script out for the process: vGhettoLinkedClones.pl

This is using the new vSphere API and modification of vmclone.pl that is part of the current VI Perl Toolkit Utilities

You can use the script if you have access to vSphere BETA, else you'll need to wait until vSphere GA's.

=========================================================================
William Lam
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at: http://engineering.ucsb.edu/~duonglt/vmware/
vGhetto Script Repository
http://twitter.com/lamw



If you find this information useful, please award points for "correct" or "helpful".

1) Generally with Linked Clones you'll have a single gold/master image and then you'll create few dozen or so Linked Clones, you will not be able to merge the deltas back to the base as you can see there will be a problem since each LC will map back to the master. With VMware View the two use cases are (non-persistent and persistent LC's).

With non-persistent you will not be keeping the user's state of the OS, this is great for a lab environment where each night or morning user's will always get a fresh OS and changes on the system will not persist and in VMware View this operation is called "Recompose" and it's similar to that of our script where we take an additional snapshot on the Linked Clone and the VM is reverted back to the original Linked Clone via the pristine snapshot that was taken after the LC was created.

persistent on the other hand is achieved by adding a user disk which uses application redirection to store all changes from the user to their respective data disk and the OS disk continues to reference the gold/master image.

You'll need to write some logic for the second case but that's generally how it works and how VMware View 3 provides Linked Clones support.

2) There are no VI API support for Linked Clones on a standalone ESX/ESXi host, you'll need to vCenter instance and the only available method that supports this is the one I've described in an earlier post.

=========================================================================
William Lam
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at: http://engineering.ucsb.edu/~duonglt/vmware/
vGhetto Script Repository
http://twitter.com/lamw



If you find this information useful, please award points for "correct" or "helpful".

I don't think you completely understand how Linked Clones work, you will not be able to merge the individual LC's into the base image as each LC uses the base image as an OS references and all differentials of each VM is written to it's individual delta file. The commonality between all the LC's is the common base OS, if you try to merge you'll probably lock the rest of the LC's out from functioning.

You may want to go through some of the VMware View 3 documents that describe Linked Clones in greater detail to get a better understanding and here is a quick snippet when View 3 was released that gives you some high level information: http://vmetc.com/2008/12/07/vmware-view-30-perspective-from-the-implementation-angle/

From my previous post you have 2 options, If you're looking to preserve user's data you'll need to create a second data disk that is attached to each VM OR you use full clones and not Linked Clones, remember LC's aren't for everyone, depending on your use case. Non-persistent LC's are great in a lab environment and this is something that I've worked on with my colleague Tuan at UCSB ResNet: http://communities.vmware.com/docs/DOC-9201

When creating Linked Clones, the base image must be off this is the same exact requirement in VMware View 3, you will not be able to Link from a running VM as the disk is locked and you'll need to take a snapshot. One big question that comes up is how do you patch Linked Clones, currently if you have a master image of WinXP-SP2 and you have 20 LC's linking off that base image, if you want to go to WinXP-SP3, you'll need to update your master and redeploy the 20 LC's again as the changes to the base are different from when you created the LC's originally. In VMware View 3, you provide a master image, that master image is actually fully cloned into what they call a replica, from this replica your LC's are then linked. This then allows you to keep sort of a master template in a sense because your image is not being linked, it's cloned and then linked.

Here is another page of diagrams that might have with the concept: http://rodos.haywood.org/2008/12/storage-analysis-of-vmware-view.html

View 3 will automatically help with this process and there is a recompose operation that aids in this when you need to create a new pool based on a new base/parent image.

Hopefully this answered your question and I do suggest going over some of the documentation on how LC's work and that should give you a better idea on how you potentially might implement this in code using the VI API

=========================================================================
William Lam
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at: http://engineering.ucsb.edu/~duonglt/vmware/
vGhetto Script Repository
http://twitter.com/lamw



If you find this information useful, please award points for "correct" or "helpful".

First off, you will NOT be able to create Linked Clones from a VMware template, it has to be a powered off VM with a base snapshot. Secondly, it's fine that you delete your LC(s) after a user logsoff or what not, but again you will not be able to merge the deltas from your LC(s) to your base image. You need to understand that the base image is to be left alone, if there are changes in the LC(s), then you need to store that in an external user data disk. It sounds like your use case may be more suited if you look into full clones but if you're hosting a lab type environment, then you'll get more bang for your buck and some storage savings by using Linked Clones, you just need to know that since this works off of a snapshot, as user's are modifying the system the snapshot will continue to grow and you need to monitor this. That's why in View 3, there's an option that will refresh or revert all changes a user has made and spin up a new LC. We do that currently today, by running a nightly revert on the snapshot to bring it back to a pristine state and all user data is stored on a remote drive as user's are authenticated in through AD and they have their personal drive mounted automatically.

If the above is not what you're looking for, then perhaps full clones can be leverage. Full clones is basically full copies of an image and IF you have vCenter, you can deploy clones from a template or from live running VM(s). State is preserved unless you set the disks to be non-persistent and upon a shutdown/startup the changes will disappear, a reboot will not delete the changes.

It might also help explain your exact use case for deleting the VM(s) after a user has signed off, it sounds like you want to keep a pristine image each time but you also want to preserve some state? Again, if you want user's to be able to save some state, you'll need an additional user data disk or some type of mapped drive based on AD permissions. Hopefully this clears up a few things and again VMware View 3 implements the solutions I've discussed through a user friendly interface and if you're looking to manage a significant amount of desktops, you may want to look into that tool vs. trying to write your own. (Remember Linked Clone functionality through the VI API is ONLY available in the new vSphere product) so with today's vCenter 2.5 and ESX(i) 3.5 you'll need to look into VMware View 3 for Linked Cloning

=========================================================================
William Lam
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at: http://engineering.ucsb.edu/~duonglt/vmware/
vGhetto Script Repository
http://twitter.com/lamw



If you find this information useful, please award points for "correct" or "helpful".

Its out today: http://www.vmware.com/support/developer/vc-sdk/visdk400pubs/ReferenceGuide/index.html

=========================================================================
William Lam
VMware vExpert 2009
VMware ESX/ESXi scripts and resources at: http://engineering.ucsb.edu/~duonglt/vmware/
vGhetto Script Repository
http://twitter.com/lamw



If you find this information useful, please award points for "correct" or "helpful".