Corrupted vmdk and vmsd files

I wanted to blog here about a silly mistake I made yesterday.

I need to expand a VM’s disk and was using the ol’ vmkfstools -X. However, I obviously do this all too flippantly and forgot to check if there was any snapshots. oops. That sunken feeling.

I corrupted the vmdk and the snapshot vmsd file.

Here’s how I fixed it all.

Firstly I couldn’t run anything against the original vmdk file, as it kept saying the file was locked by the host. I unregistered the VM from VC, put the ESX server into maintenance mode (which moved all the VMs off to other hosts in the clustering – fully enabled DRS) and power cycled the host. This remove the lock on the file thankfully.

The original vmdk had been 20GB before I tried expanding it to 30GB. So I created a new 20GB vmdk:
# vmkfstools -c 20G -d thick silver1.vmdk

I then copied the contents of the broken 30GB disk into the new one:
# dd if=silver-flat.vmdk of=silver1-flat.vmdk bs=1048576 count=20480

Moved the old vmdk and renamed the new one:
# vmkfstools -E silver.vmdk silver.vmdk.old
# vmkfstools -E silver1.vmdk silver.vmdk

All the snapshots rely upon a CID and a parentCID in their -00000x.vmdk files. I opened both snapshot disks to record the details.
# cat silver-000001.vmdk
# cat silver-000002.vmdk

Basically, 000002 parentCID is 000001’s CID. In turn 000001 parentID was set to point to the original vmdk. So I had to edit the new vmdk file and set this CID.
# vi silver.vmdk

I was then able to power on the VM. Phew!

However the snapshots were still screwed up. When I tries to commit the snapshots with:
# vmware-cmd silver.vmx removesnapshots

It thought it didn’t have any snapshots, but it was clearly using the two additional vmdk disks. The vmsd file was also corrupted. So I renamed the existing one:
# mv silver.vmsd silver.vmsd.old

Then I created a new snapshot, to re-generate a new vmsd file:
# vmware-cmd silver.vmx createsnapshot recreate_vmsd

And finally I could commit the snapshots:
# vmware-cmd silver.vmx removesnapshots

Now all that was left was to increase the disk:
#vmkfstools -X 30G silver.vmdk

I guess I won’t be doing that in a hurry again 🙂

4 thoughts on “Corrupted vmdk and vmsd files

  1. So if I have a problem with vcenter having a snapshot in snapshot manager (when there isnt one cause I had to clone it – the options was greyed out on or off) I could just recreate the .VMSD file and it should all be fine?

  2. Hi Chad,
    Personally, I would try to create a new snapshot then delete it at the CLI first. This should stop it thinking there are any previous snapshots.
    If you get really stuck, you can afford a few minutes downtime, and you don’t need any snapshots in the clone, you could:
    – shut it off
    – unregister it in vCenter
    – create a new VM in vCenter in a different datastore (or if you only have 1 datastore, then rename the old folder first)
    – move the VMDK base files from the old folder to the new folder from the vCenter GUI (this copies the flat file and descriptor file)
    – edit the new VM’s settings to add the existing disks now in its folder

    Hope that helps.

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  4. We use ESXi 5 U2 – simply powering off VM, remove from inventory, readd to inventory resolved this issue for us

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