A lot of people I've met new to
UNIX are afraid of using
octal permissions with
chmod. Forget everything you've read about them because here is how simple it really is.
4 = read
2 = write
1 = execute
To get a specific permission, simply add them up.
Read and Execute = (4+1) = 5
Execute and Write = (1+2) = 3
You need at least 3 of these numbers, one for what the Owner, Group and Other can do to this file, in that order.
So when you see a "chmod 751 runme", you know that the owner of the file can read, write and execute (4+2+1). The group that owns this file can read and execute (4+1), and everyone else can only execute this file (1).
The average UNIX user doesn't need to know this, but you will feel better knowing exactly what's going on and still be able to impress all of your friends with your guruness.