I would use 'man vmkfstools' to get the manual page and some examples on its usage. Also you may wish to place a backslash in front of the : in the name of the vmhba. I.e. vmhba32\:2\:51\:1 as colons mean something to the shell. Also, you may want to use 0 as the partition or drop the partition altogether if there is nothing else on that LUN.
Edward L. Haletky
VMware Communities User Moderator
Author of the book 'VMWare ESX Server in the Enterprise: Planning and Securing Virtualization Servers', Copyright 2008 Pearson Education.
As well as the Virtualization Wiki at http://www.astroarch.com/wiki/index.php/Virtualization
It works with:
vmkfstools -r /vmfs/devices/disks/vmhba32:2:51:0 /vmfs/volumes/oDatastore/xpto/xpto.vmdk