CHMOD

symon · Posted: Sun Apr 23, 2006 7:59 pm Post subject: CHMOD

CHMOD Permissions Settings - Definitions and Overview
To change a file or directory's permissions, use the UNIX 'chmod' command
(which actually stands for 'change mode').

CHMOD Permissions Settings

Permissions Settings - Definitions and Overview

In order for your CGI program to run, it must be executable by the server. Therefore, you must set the permissions so the server can read or execute your files, which usually means making your CGI programs world executable. The way you set your file permissions is by using the CHMOD commands.

The CHMOD's permission mask is a three-digit number. Each digit of the number defines the permission for a different user of the file. The first digit defines the permission for the owner, the second digit defines the permissions for the group and the third digit defines the permissions for everyone else (referred to by CuteFTP as public). Each digit works the same for each group of users: the owner, group, and public. What you set for one digit has no effect on the other two digits.

Owner = the files users (you)
Group = the files group
Others = others

Permissions Definitions:
r = read access x = execute access w = write access

Numerical Definitions:
r = 4 x = 2 w = 1

You will come to recognize, if you do not already, Chmod as a word used for changing Permissions from within Telnet or your FTP client.

Some scripts will tell you to chmod 775 (for example). When using the numeric system, the code for permissions is as follows:

4 + 2 + 1 (rwx) = 7

The first number applies to Owner, the second number applies to Group, and the third number applies to Others. Therefore the first 7 of the chmod 775 tells Unix to change the Owner's permissions to rxw (because r=4 + w=2 + x=1 adds up to 7, this giving the Owner Read, Write, and Execute Permission. The second 7 applies to the group, this giving the Group Read, Write, and Execute Permission, and the last number 5, refers to Others (4 + 1= 5), giving Others only Read and Execute Permission. The permissions for chmod 775 look like this: rwx rwx -rx.

Permissions are always broken up into three groups of letters, however if there is a dash, this dash simply means that Permission wasn't given for that particular function, for example in the chmod 775, Permission to Write was not given to Others.

Remember: the first 3 letters always apply to Owner, the second 3 apply to Group, and the third 3 apply to Others.

CHMOD and File Permission Settings
400	r--------	files (won't let you accidently erase)
444	r--r--r--	files (lets everyone read
600	rw-------	files (no one else can read or see files
644	rw-r--r--	files (getting the idea?)
664	rw-rw-r--	files
666	rw-rw-rw-	files, (note: this could allow havoc of satanic proportions)
700	rwx------	programs and directories
750	rwxr-x---	programs and directories
755	rwxr-xr-x	programs and directories
777	rwxrwxrwx	programs and directories
Note: 777 will produce a wide open executable script, this is dangerous!

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