Messages in this thread | | | Date | Thu, 14 Feb 2008 16:19:42 +0100 | From | Hans-Jürgen Koch <> | Subject | Re: Is there a "blackhole" /dev/null directory? |
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Am Thu, 14 Feb 2008 16:00:06 +0100 (CET) schrieb Jan Engelhardt <jengelh@computergmbh.de>:
> > On Feb 14 2008 10:46, Andi Kleen wrote: > >Jasper Bryant-Greene <jasper@unix.geek.nz> writes: > >> > >> This could be done fairly trivially with FUSE, and IMHO is a good > >> use for FUSE because since you're just throwing most data away, > >> performance is not a concern. > > There is a much more interesting 'problem' with a "/dev/null > directory". > > Q: Why would you need such a directory? > A: To temporarily fool a program into believing it wrote something. > > Q: Should all files disappear? (e.g. "unlink after open") > A: Maybe not, programs may stat() the file right afterwards and > get confused by the "inexistence". > > Q: What if a program attempts to mkdir /dev/nullmnt/foo to just > create a file /dev/nullmnt/foo/barfile? > A: /dev/nullmnt/foo must continue to exist or be accepted for a while, > or perhaps for eternity.
Well, the problem seems to be that a "directory" is not just data but also contains metadata. While it's easy to write data to /dev/null, you cannot simply discard metadata associated with a directory. So, such a "/dev/null-directory" would have to remember metadata (at least all created filenames including subdirectories) in the same way as other filesystems do. Only file _content_ can be discarded. To be honest, I still cannot see many sensible usecases for that...
Thanks, Hans
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