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In a Linux server I will have an user with gid=0 but it's uid won't be 0. As there are many commands with root:root and execute permissions for group I know there will be a lot of administrative task that this user can't do because many programs checks at start if UID=0

Anyone knows what commands/tasks can't do a user with UID!=0 and GUID=0? That user could mount filesystems or change passwords...?

For example, the user can't read messages as it has only read permissions for root owner. I know the question is open.

Many thanks!

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migrated from serverfault.com May 24 '13 at 15:24

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marked as duplicate by Gilles, jasonwryan, vonbrand, slm, Anthon May 25 '13 at 3:24

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1 Answer

It depends highly on the configuration of the system. If an application has permissions like root:root 0770, users with the root group can execute it. If it has permissions like root:root 0700, they can't. There isn't really a standard for this kind of thing, and a simple chmod (or chown) command can change it.

Unless the suid bit is set, the program in question will run with the permissions of the user that launched it (eg. in this case non-root, but with the root group).

Users other than root can never do things like bypass filesystem permissions or change ownership of a file to another user, whether they have the root group or not. They also can't mount filesystems which are not in fstab.

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I was talking about "the logic" of some administrative commands that I have execute permissions for my group root. I know there are some commands that return an error if it is NOT executed with user UID=0 event you have permissions for execute it. I know this question is very strange :) –  RuBiCK May 24 '13 at 12:00
    
It's not strange. However, it is completely implementation defined. –  Falcon Momot May 24 '13 at 12:39
    
Only to discuss a little more.. :) –  RuBiCK May 24 '13 at 13:00
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