Multiple *NIX Accounts with Identical UID
- by Tim
I am curious whether there is a standard expected behavior and whether it is considered bad practice when creating more than one account on Linux/Unix that have the same UID. I've done some testing on RHEL5 with this and it behaved as I expected, but I don't know if I'm tempting fate using this trick.
As an example, let's say I have two accounts with the same IDs:
a1:$1$4zIl1:5000:5000::/home/a1:/bin/bash
a2:$1$bmh92:5000:5000::/home/a2:/bin/bash
What this means is:
I can log in to each account using its own password.
Files I create will have the same UID.
Tools such as "ls -l" will list the UID as the first entry in the file (a1 in this case).
I avoid any permissions or ownership problems between the two accounts because they are really the same user.
I get login auditing for each account, so I have better granularity into tracking what is happening on the system.
So my questions are:
Is this ability designed or is it just the way it happens to work?
Is this going to be consistent across *nix variants?
Is this accepted practice?
Are there unintended consequences to this practice?
Note, the idea here is to use this for system accounts and not normal user accounts.
