Hi. I'm learning linux and decided to go with Slackware(I'm having a much more enjoyable time with it then I did a year ago trying to learn Fedora Core). I'm reading the slack book and so far I have had no problem understanding it. However, when I got to the section about permissions I became a bit confused. I understand how permissions work,the number and letter system,and how to set them,but I do not understand the set user id and set group id options. I'm not exactly sure what they do,and I was wondering if someone would mind explaning them. The sites I googled didn't help me much,either. For example,what would typing chmod 6755 do? Thanks for your help.

For files:
setuid: When executed the program will run as if the user who owns the file was running it
setgid: When executed the program will run as if it were a member of the file's group

For Directories:
setuid: No effect
setgid: When a new file is created in the directory, the new file will have the same group owner as the directory

Didn't ask about stickys so i assume you know about them

as for chmod 6755 you say you understand the number system for setting permissions so you understand that a regular chmod 755 would set permissions to rwx,r-x,r-x.

The fouth (first in line) bit works in a similar fashion

4000 is the setuid permission

2000 is the setgid permission

1000 is the sticky permission

therefore 6755 sets permissions to rws,r-s,r-x i.e. regular 755 permissions with the extended setuid and setgid permissions.


phew...now i feel less guilty about saying the following...

Bollocks. You didn't look very far

or try `man chmod`

Hi. I guess I just needed it explained a bit better,I understand it now. Thanks for your help.