rm /etc/resolv.conf
You should be told Permission denied. /etc/resolv.conf is an essential system configuration file; you aren’t allowed to change or remove it unless you’re root. This keeps you from accidentally messing up the system, and if the computer is a public one (such as at an office or school), it keeps users from messing up the system on purpose.
Now type ls -l /etc/resolv.conf.
This will give you output that looks something like this:
-rw-r-r- 1 root root 119 Feb 23 1997 /etc/resolv.conf
The -l option to ls requests all that additional information. The info on the right is easy: The size of the file is 119 bytes; the date the file was last changed is February 23, 1997; and the file’s name is /etc/resolv.conf. On the left side of the screen, things are a little more complicated.
First, the brief, technical explanation: The -rw-r-r- is the mode of the file, the 1 is the number of hard links to this file (or the number of files in a directory), and the two roots are the user and group owning the file, respectively.
So that was cryptic. Let’s go through it slowly.
7.1.1 File Ownership
Every file has two owners: a user and a group. The above case is a little confusing because there’s a group called root in addition to the root user. Groups are just collections of users who are collectively permitted access to some part of the system. A good example is a games group. Just to be mean, you might create a group called games on your computer and then set up your system so that only people in a games group are allowed to play games.