Linux – File Ownership and Permissions

Akkkk. Linux file permissions drive me crazy. Yes they are completely necessary (or so I am told) but I feel like I fight with them all the time.

Here is my cheat sheet for viewing and changing permissions:

View Owner and Permissions

ls -l or ls -l filename

It shows the permission settings, grouped in a string of characters (-, r, w, x) classified into four sections:

File type. There are three possibilities for the type. It can either be a regular file (–), a directory (d) or a link (i).
File permission of the user (owner)
File permission of the owner’s group
File permission of other users

chown [OPTIONS] USER[:GROUP] FILE(s)

The following example will change the ownership of all files and subdirectories:

chown -R user:group /file/path/

-R means recursive

In symbolic notation, we provide chmod with a comma-separated string using references for user (u), group (g) and others (o).

We can set these same permissions with the symbolic notation:

chmod u=rwx,g=rw,o=r <document.docx>

the privledges you can give are r, w, and x, for read, write, and execute

What about these numbers? basically the same thing – you can do:

chmod 764 filename

Where each of the three numbers above are User Owner Group permissions – equivalent to the chmod u=rwx,g=rw,o=r example above

With the numbers:
7 = read, write, and execute

6 = read and write

5 = read and execute

4 = read only