Here is how you do it
USE THE TERMINAL OPTION mdutil.
It has a switch, -i, to enable indexing on a volume. So I just went ahead as root (sudo bash) and ran:
sudo bash. (my network drive example is named "ldm" so replace ldm by your network drive name)
mdutil /Volumes/ldm -i on
Then I checked the status with
mdutil /Volumes/ldm -s
And, behold ... I got back the following:
/Volumes/ldm/:
Status: Indexing Enabled
A second later, the Spotlight Icon started pulsating. Half an hour later, it stopped. I went to a Finder window, typed a query, and selected the network volume ldm. To my delight, matches were coming back instantaneously on files deep down in the file hierarchy on that volume. I have not checked whether newly added files are indexed on the fly, too, and I do not know where the .Spotlight-V100 file is stored (not in the root of the volume in question it seems).
I thought that others may give it a try to confirm whether this is working as expected. The volume I tested this with was an AFP volume served via NETATALK (v. 2.0.2) by my Linux server (a x86 debian box). Unfortunately, it appears to fail with SAMBA. I have not checked NFS. One caveat: you must rerun the mdutil command each time the volume is mounted.
Hope it helps someone!
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