why root? (was Re: How does 'mv' rename directories?)

[Randal Schwartz]

In article <4195 at buengc.BU.EDU>, bph at buengc (Blair P. Houghton) writes:
[...much much gibberish deleted...]
| Moving from one partition to the next requires a copy-then-unlink,
| whereas moving within a partition only requires a link-then-unlink.
[...]
| But, basically, there's no need to become uid 0 when you're just moving
| files around in a partition.

>From link(2)[sunos3.2]:

"With hard links, both files must be on the same file system.  Unless
the caller is the super-user, the file named by [the first parameter]
must not be a directory...."

I cannot, as J. Random Luser, write a program that renames a directory
because I cannot do the link/unlink pair that you mention ....unless I
have the rename(2) system call, in which case mv(1) is indeed not
setuid root, because it can be done in simple user code.  The original
question was probably regarding a system that hasn't incorporated the
rename(2) system call (originally in 4.0BSD, I think), and *requires*
root privs to rename a directory.

Enough bogosity.  Think of all the things mv does.

Just another UNIX hacker,
-- 
/== Randal L. Schwartz, Stonehenge Consulting Services (503)777-0095 ====\
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