GNU and Unix systems are set up to allow many people to use the same
computer, while keeping certain files private or keeping certain
people from modifying certain files. You can verify this for
yourself. Log in as yourself, i.e. _NOT_ as root.
whoami
This verifies that you are not root. Then enter the following
command:
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.