I have setup a test vmware 4 environment at home, using esxi4. The setup consists of a few virtual machines, two esxi servers and a storage box.
Today, i found that a couple of machines were not booting correctly due to the datastore they lived on running out of free space. I created a few snapshots a while ago but did not remove them so had built up over time. Do not try the same on a live environment. Mine was just a test environment.
Anyway, the error which appeared is shown below 
I had the option of extending the datastore which would have resolved the issue, but decided to resolve the difficult way.
I tried removing all snapshots but received error below: Click to enlarge
‘The operation cannot be allowed at the current time because the virtual machine has a question pending: There is no more space for virtual disk. You might be able to continue this session by freeing disk space on the relevant volume and clicking retry.’
I tried migrating but obviously couldn’t due to a snapshot being attached.
I tried powering down the machines so i could attempt to remove the snapshots, but machine would not power down.
Finally, i decided to kill the machine so enabled SSH on the esxi host the machines were sitting on. Instruction on how to enable SSH can be found at https://cloudbuild.co.uk/?p=1531
1) Logged onto the esxi 4 host using putty. The below also works with esxi5
2) I typed ps | grep vmx
The command above listed the vmx’s on the host. See screen shot below. Your output should be similar.
3) The first column lists the PID and the second contains the parent PID. Make a note of the Parent PID in the second column for the VM you are experiencing issues with.
Please take a note of the correct parent PID as you could shutdown the wrong VM.
4) I typed kill ‘Parent PID’ – replace parent pid with the id you noted in step 3. Press enter
5) Wait for a few seconds and carry out step 2 again, to check whether the machine has disappeared.
6) My results showed that i had successfully killed the VM parent PID. If you find that the parent pid still exists, give it a minute. If the issue still exists, try kill – 9 ‘Parent PID’ replace parent pid with the id you noted in step 3. Press enter
7) After carrying out the above steps, i was able to remove the snapshots succcessfully and migrate the machine to a larger data store.
Thank you. Spot on instructions. Perfect.
Perfect instructions. Thank you.
Thank you for this instruction. Great job…
Thank you for instructions, very useful.
Fantastic, short and sweet, did the trick, Thanks a lot…