Chmod review.

With more and more people using the command line, changing permissions is a must. Chmod (chmod) is used to change permissions of a file. Do not use it that much except when setting permissions on the .ssh folder or on a web server application directories


i.e.
$ sudo chmod -R 755 appdirectory

or

$ chmod 700 ~/.ssh
$ chmod 600 ~/.ssh/*

Explanation examples:

Permissions			Command
User	Group	World
rwx	rwx	rwx	chmod 777 filename
rwx	rwx	r-x	chmod 775 filename
rwx	r-x	r-x	chmod 755 filename
rw-	rw-	r--	chmod 664 filename
rw-	r--	r--	chmod 644 filename

r = readable  w = writable x = executable  - = no permission


Here is another way of looking at it:

ugw	---	function
400	r--	read by owner
040	-r-	read by group
004	--r	read by anybody (other)
200	w--	write by owner
020	-w-	write by group
002	--w	write by anybody
100	x--	execute by owner
010	-x-	execute by group
001	--x	execute by anybody

To get a combination, just add them up. For example, to get read, write, execute by owner, read, execute, by group, and execute by anybody, you would add 400+200+100+040+010+001 to give 751.

There is also a nice web based calculator you can use on a web page of your own making: http://wsabstract.com/script/script2/chmodcal.shtml

Note: Some people like to use:

chmod ugo=rwx myfile

Where the nerds use:

chmod 777 myfile