Mean of 'S' in front of permission on the ls command

swamprat · 05-15-2007, 09:05 PM

Hello all,

I saw the following while doing an ls -la command and I don't know what the 'S' means in front of the permissions.

Newbie - Suse 9.2

srwxrwxrwx 1 root root 0 2007-05-15 21:04 X2

Thanks

GrapefruiTgirl · 05-15-2007, 09:25 PM

The S is the 'SUID' bit. It means that when someone runs the program, it runs with ROOT permissions (or with the permissions of its owner, in that case, ROOT).
Do some Googling about Linux File Permissions for further details, and also read the man pages for 'chmod' and 'chgrp' for more related info.

As in the 'su' command, which means 'Switch User', the SUID bit implies 'Switch User I.D.'.

S can also mean GID or STICKY, depending on its location amongst the rwx's. You can also read about this when you Google File Permissions.

gilead · 05-15-2007, 09:54 PM

In the example you give of srwxrwxrwx, X2 is a socket. If it was a file with the suid bit set it would have permissions similar to the sudo command where the execute bit for user is set to s instead of x:

Code:

$ ls -l /usr/bin/sudo
-rws--x--x 1 root bin 90400 2006-02-07 05:00 /usr/bin/sudo

Have a look at http://rute.2038bug.com/node17.html.gz for a description of permissions for files, directories, etc.

GrapefruiTgirl · 05-16-2007, 04:21 AM

@ Gilead -- thank you for the correction; once again, I learn something new

as the 'socket' aspect clearly slipped right by me in the wee hours! My apology to Swamprat for any misdirection.