Permissions

Here’s a single file from our ls -l file listing earlier. I’ve tweaked the permissions to make this example more illustrative:

rwxr-xr-x 1 root root  386 Aug  2 13:14 os-release

Specifically, look at the permission bits:

rwxr-xr-x

They are displayed in three groups of three here. Imagine them separated into three groups, to make it easier:

rwx r-x r-x

Each of these triplets represents read (r), write (w), and execute (x) permissions for a specific set of users, based on the user and group ownership information for that file. If you see a - character in place of a letter, that action (for the set of users it applies to) is not permitted. Let’s look at them in more detail:

1. The first three bits represent the permissions of the file owner. In this case, the file’s owner (root) can read, write, and execute the file – rwx.
2. The second three bits represent permissions for the group owner of the file...