VMWare: Cannot open the disk… The parent virtual disk has been modified

here the complete problem description:

we had a vmware-guest machine which had one snapshot running for a long time. we wanted to increase the disk space for this machine but we didn’t recognize that there extisted a snapshot.

at first we wanted to increase the space over the vmware virtual infrastructure client but the original size always was reset… so we decided (before we knew we had a snapshot) to increase the disk with vmkfstools – this was a great failure because after increasing the vmdk the following error occured:

“Cannot open the disk ‘/vmfs/volumes/XXX/MACHINE/MACHINE-000001.VMDK’ or one of the snapshot disks it depends on: The parent virtual disk has been modified since the child was created.”

sh…

that was the time we knew that we had a running snapshot…

so, what to do? vmkfstools won’t change the disk size back to the size it was. fortunately we exactly knew the size of the file before our increase!

after some search we wanted to split the .vmdk at the size it was but split is limited to a file size of 2gb and we had a 5gb big .vmdk. dd was our friend! :)

dd if=MACHINE-flat.vmdk of=./splitted/MACHINE-flat-cut.vmdk bs=51712K count=100

e voila – the original file size has been “restored”. ;)

the only thing we had to do now was to write the original extent size to the vmdk as follows:

RW 10477216 VMFS “MACHINE-flat.vmdk”

after a short start of the machine – it ran! :)

what to learn about this problem? always look if there exists a running snapshot!