This step is optional and if you are happy with the ext3 filesystem then you can safely skip it.
I would highly recommend for this to have a remote console on the system as in most of the cases the auto fsck will fail and you will have to run it manually from the console.
Be sure to back up your data Before upgrading your system, it is strongly recommended that you make a full backup, or at least back up any data or configuration information you can't afford to lose.
The upgrade tools and process are quite reliable, but a hardware failure in the middle of an upgrade could result in a severely damaged system.
You need NOT to make any changes to this file until and unless you need extra repositories for your setup.
Type the following apt-get command: in addition to performing the function of upgrade, also intelligently handles changing dependencies with new versions of packages; apt-get has a “smart” conflict resolution system, and it will attempt to upgrade the most important packages at the expense of less important ones if necessary. The /etc/apt/file contains a list of locations from which to retrieve desired package files. It works like Microsoft or Red Hat update manager i.e.