Privilege UID

[Caroline_11]

Hi, I know thant UID from 0 to 99 are privilege account but what type of privilege ? R, X or W ... For exemple UID 20

[Steven E. Protter]

User id 0
zero

Its God
root
all powerful
can do anything.

When I say anything, I mean it can wipe out a whole system with one command and no warning message.

The other reserved user id's are normal user id's reserved for daemons and applications.

more /etc/passwd

will give you an idea.

You should not use UID's below 100 for anything, the system needs them. If you add in a product such as cifs/9000 it might want one of those low user ids.

The function of non-zero UID's varies depnding on purpose.

SEP

[A. Clay Stephenson · Accepted solution]

The only hard and fast UID across all flavors of UNIX/Linux is UID 0 - root. The others can vary a bit as to the specific UID for bin, adm, lp, sys, uucp. There are also reserved GID's as well. For example, GID 7 is used across almost all flavors for lp, regardless of the UID for lp. By convention, normal UID's start at 101 but you should be aware that Linux considers UID below 1000 to be reserved. If you are starting from scratch, it's probably wise to respect the Linux convention in case you need to have users that span UNIX flavors.

There is nothing to prevent from using a low UID but you are setting yourself up for possible trouble later.

You should decouple your thinking from associating accounts with file permissions (r,w,x); reserved accounts are best thought of as unifying a number of related files (e.g. the lp subsystem) so that, for example, setuid/setgid programs execute properly.