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SubjectRe: Can't hardlink in different dirs. (BUG#826)
On Fri, 3 Dec 1999, Andrea Arcangeli wrote:

> For what exactly is it an handy feature? I never needed to hardlink to a
> file that I don't own, so you would convince me if you would raise good
> points.

It's a handy feature to piss off other users when quotas are on the file
system: you hard link every single bit they have in their home directory.
The users vulnerable to this must have world/group access to their home
directory, but most lame users have. A lame user won't notice that all
his file have a link count of 2. From time to time he will delete files
and create new ones (which you dutifully hard link). After a while he'll
end up with an empty directory and still has his quota exceeded.

But don't do this if the system administrator is anyone else than your best
buddy.

To be more serious: most of the time hard links between directory exist
if users have a low quota and need programs that aren't installed system
wide (usually for some reason). This way they share the size (I install
program X, and you install program Y, and we add a few hard links here and
there...). I know that the same goal can be achieved by using soft links, but
they have the fame of having a large overhead. This is a point for NFS
filesystems over a single 10Mbit ethernet with 40 diskless machines.

Then there are some ill scenarios where hard linked suid programs can be
used if the admin is too lazy to create the desperately needed groups which
would allow access to a common directory with the original files.

--
Klaus Espenlaub Email: espenlaub@informatik.uni-ulm.de
Universitaet Ulm Phone: +49 731 50-24178
Abteilung Rechnerstrukturen Fax: +49 731 50-24182
D-89069 Ulm Office: Building O27, Room 316

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