We’ve had this error on ESX 3.5 and 4.0 hosts, both ESX and ESXi.
When trying to add a new NFS datastore we get the above error message, both in the vSphere Client and when using the command-line tools.

Logging on to the Service Console on an affected host, “esxcfg-nas -l” also results in the same error.

The cause is invalid entries in the /etc/vmware/esx.conf file. Fortunately, it seems to be possible to remove the bad entries and the host then starts working properly without a reboot.

In our case, the bad entries looked like:
/nas/./enabled = "false"
/nas/./host = "1"
/nas/./share = "0"
whereas valid entries are recognisable:
/nas/vmdesktop/enabled = "true"
/nas/vmdesktop/host = "10.0.0.100"
/nas/vmdesktop/readOnly = "false"
/nas/vmdesktop/share = "/vol/vmdesktop"

As I mention above, fixing it on ESX isn’t too hard, just edit /etc/vmware/esx.conf using nano or vi as root, being careful not to affect any other lines.

On ESXi, it’s a little more tricky as you can’t readily log on and edit files without enabling Technical Support mode.

It is, however, possible to edit esx.conf via the Remote CLI (Linux or Windows) or using the vMA.

Below are some example commands which grabs the esx.conf file, edit it using ‘sed’, and then put the altered file back on the host.

vifs -get /host/esx.conf work.conf
cat work.conf | sed -e '/\/nas\/\./d' > fixed.conf
vifs.pl -put fixed.conf /host/esx.conf


The ‘sed’ command will probably need to change for you, depending on what the invalid lines look like. You can just use nano or vi on Linux or the vMA to do the edit, but if you’re using Windows you may find that Notepad and Wordpad either don’t display the file clearly or convert the line endings from Unix format to DOS. Using the free VIM for Windows (http://www.vim.org/download.php) will let you keep the file in the same format.

After making those changes, it was possible to add NFS datastores as normal.