Manually revert snapshot esxi 5.5

I have a VM that is running on a snapshot that i need to revert. However there is not enough diskspace on the datastore to revert the snapshot. "An error occurred while reverting to a snapshot: msg.disklib.NOSPACE."

Is there a way to manually delete the delta file and have the system boot from the previously created snapshot?
Coriron HazManaging DirectorAsked:
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
I'm afraid you must go through the procedure, you cannot just manually delete files from the datastore, without causing corruption to the virtual machine disk files.

Please see my EE Article for more info on snapshots.

HOW TO: VMware Snapshots :- Be Patient

Do you want to revert or remove all the snapshots, snapshots are dangerous, if you run out of datasore space, please also not performance of he VM will be poor running on a snapshot.

Is the VM off ?
Coriron HazManaging DirectorAuthor Commented:
I want to revert the snapshot. The machine is currently off. As I said, if I "go to" the snapshot in the snapshot manager of will not let me revert as the data store is full (there is nothing else on the data store other than this VM, so freeing up disk space is not an option)
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
I'm afraid you will need to free up space on the datastore, this is the danger of using snapshots which can fill up the datastore.

you may be able to turn off other VMs, which will free up some space, when the memory VM swap files are removed.

So you could try turning off all VMs, and try again.
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Coriron HazManaging DirectorAuthor Commented:
Unfortunately this is the ONLY VM running on the host. (It's a bodge job because the customer didn't want to spend money and we have to restore the snapshot every 2 weeks to avoid a database issue. It was the difference between a 3k fix and a 40k fix that they weren't willing to spend. This is the result. Grr. )
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
As snapshots can grow at a rate of 1GB per hour, even if you could power on the VM, time would be limited before the VM would stop, because you have no space on the datastore.

Snapshots are not backups, and you should be backing up the VM, and backup and restore, snapshots are not designed for this purpose.

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Coriron HazManaging DirectorAuthor Commented:
Yeah...tried explaining this to the customer...they aren't interested. Oh well....rebuild it is! Thanks Andrew
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Maybe you should state, that it could cause virtual disk corruption and the VM would be lost forever!

and there is nothing you can do or anyone else, do you still want to risk it ?
Coriron HazManaging DirectorAuthor Commented:
Good point. I'll leave the ball firmly in their court and see what they want to do. If nothing else then this incident proves my point.
Coriron HazManaging DirectorAuthor Commented:
I assume there is no way to manually edit the vm / vmdk to point at the xxxxx-flat.vmdk instead of the delta?
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Yez, past risk back to them for Action, you can only advise, "you can lead a horse to water......"
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
You can modify the VMX file, but the end results, may not be what you desire, you could have a corrupt virtual machine disk, which does not boot, if it did boot it certainly would be missing all the changes in the delta.

If desperate times, and you have no other choices, or datastore to move to, or VMs to shutdown...
Coriron HazManaging DirectorAuthor Commented:
I'll give it a go. The original flat file was created from a backup of a physical machine. The flat file should be in a bootable state (dis-regarding any VM disk corruption that may or may not occur) I'll give this a go. Any tips / documentation you can point me in the direction of? If not i'll just go it alone. (i have a rough idea how to achieve this)
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
It's a quite straightforward, just add the VMDK (parent) file to the VMX and power on.

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