Incremental backup

[Karthik_sg]

All i need to know how we perform a incremental backup .Please explain it with steps.Thanks in advance

[Mark Ellzey]

Karthik,

Like most questions, the answer is "It depends...".

In order to perform a incremental backup, it is first necessary (manditory) to perform a full backup. How you do this is up to you. There are many tools available to backup your system; tar, cpio and amanda are just a few. There are also third-party backup applications available (for a price or free) that will do the same thing.

The first question I would ask is: what do you want to back up? Since you are asking about 'incremental' backup, I'm assuming that you mean application data.

Here's how I'd do it:
1. Write a script that shuts down your database manager and performs a full backup. Many databases have built-in backup utilities for this purpose. I'd find out which utility to use and script it. Then I'd test the script to make sure it does what I want it to do (my scripts very rarely do what I expect the first time). Then I'd create a cron job to run the script for me, say at the end of the week (Friday night, Saturday or Sunday).
2. Write, or better, modify my backup script to perform an incremental backup, based on the abilities of the utility I'm using. I would also create a cron job for this script to run on the days that I'm not running a full backup (i.e. Monday - Thursday or Friday).
3. I would document the hell out of the process. There is nothing worse than trying to restore a full backup and then not knowing which of the incrementals you need to get back to were you were before disaster struck. Keep good records.
4. Test, test and test some more. Make sure your backup can be restored. Funny how this works. We back up our data, but never restore it until something breaks. If we haven't tested our restore procedure, how will we know if it will work when we really need it?

For a good reference on backup, get the book: UNIX Backup & Recovery bye W. Curtis Preston. O'Reilly & Associates ISBN: 1-56592-642-0

Regards & good luck,
Mark

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