It looks like you're logged in as "you" and you're trying to edit the system file
/etc/fstab; that file can only be written to by the super-user (
root). To edit that file, you must know the root password and you can temporarily become root with the
su or
sudo utilities (both require the root password); e.g.,
Code:
su
Password: <type the root password>
# vi /etc/fstab
You exit
su (or
sudo) by typing
Ctrl-D or
exit at a command prompt.
If you do not know the root password, you will not be able to edit system files.
Whenever you attempt to edit a file that you do not own or a file that you do own but is read-only, the editor will want you to override with a "bang" (the exclamation point); in
vi or its derivatives, you would enter
Again, however, if you do not own or have write permission, that will fail.
Take a look at the manual pages for
su and
sudo for more information.
Hope this helps some.