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Old 06-16-2005, 01:37 PM   #1
Registered: Feb 2003
Distribution: Kubuntu
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SUID and setting 'other' permission to _ _ x

I'm studying linux and am have difficulty understanding the differences between SUID and setting the "other" permission for a program to execute.

In short, what's the functional difference between the following permission sets for a program file?

rwt rw rw and rwx rw rwx

Thanks gang
Old 06-16-2005, 05:55 PM   #2
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Re: SUID and setting 'other' permission to _ _ x

Originally posted by hpladd
rwt rw rw and rwx rw rwx
Surely you mean
t means sticky, not SUID.

But to answer the question.

The purpose of SUID is to have the executable run as
the owner, no matter who starts it.

The need for it is obvious when an application has
been compiled to require root privileges (and you
don't want to use sudo) and you want a normal user
to be able to run it, e.g. /sbin/reboot ...

Btw, your rwsrw-rw- wouldn't work, the x still needs
to be there for other.

Old 06-17-2005, 09:57 AM   #3
Registered: Feb 2003
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(I posted a reply earlier, but it hasn't shown-up. Also I hit "thanks," but that doesn't seem to have gone well either.)

Thanks Tink,

Surely I did mean s. (I still think s should stand for sticky).

I now see how SUID an SGID are similar.

All the manuals refer to SUID and its use with executables because SUID is of very limited use in any other situation. How often would it be useful to have a user A create a file and have it inherit user B's user ownership? Right?

Also SUID does not provide access to an executable it just provides the permissions to those that do access the file. Therefore if user A needs access to the executable, the "other" permissions must at least be x. But does "other" also need rw, or are those permissions inherited after access to the exe. file is obtained?

Thanks again!
Old 06-17-2005, 01:37 PM   #4
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It's explained in more detail here: in paragraph 4.1.6.


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