[Gllug] Convertng a disk (regular) file to a named pipe

[Tethys]

Adrian McMenamin writes:

>> Oh I see - there seems to be a recipe there for freebsd (which doesn't
>> involve any named pipes at all):
>
>Why is it not a named pipe? I may well have got the nomeclture wrong (this is 
>a genuine question), but this:
>
>http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?named+pipe
>
>suggests that I haven't afaics.

It's not a named pipe because... well, because it's just not.
Why is an elephant not a banana?

All it's doing is creating a block device out of a file, and then
mounting that device. No named pipes were harmed by this operation.
Under Linux, use a loopback mount to do that. Note that last time I
tried it (which admittedly was 1996/7 or so) Linux didn't support
loopback mounts over NFS, but I believe that's now been fixed. Thus
to add 1MB of swap over NFS:

	dd if=/dev/zero of=/my/nfs/mounted/file bs=1024 count=1024
	losetup /dev/loop0 /my/nfs/mounted/file
	swapon /dev/loop0

Note that since Linux supports swapping to files directly as well
as to block devices, you should in theory just be able to do:

	dd if=/dev/zero of=/my/nfs/mounted/file bs=1024 count=1024
	swapon /my/nfs/mounted/file

But see this caveat in swapon(8):

	Swap over NFS may not work.

Tet


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