Backup refers to copying of files or database of  a computer data . It may be used to restore original after data loss event. In other words we can say that we make backup of computer data so that if the computer will corrupt , we can restore data from backup files. There are mainly two types of backup . first is full backup and second is Incremental backup. A backup process is applied to critical database . The backup process is governed by predefined backup policies that specify how many duplicate copy is required and how frequently data is backed up. The policy also defined the time and location of databases. We can also use crontab to automatically scheduled the data backup.

What is Full backup and Incremental backup

Full backup :- In full backup each files and directory is written to backup media.

Incremental backup:- In incremental backup each piece of backed information is stored only once. Then successive backups only contain the information that changes since the previous one. It uses file modification time to determine which file need to backup. 

Software used to take backup:-

There are many software, which is used to take backup of our data or system. Some of software are – clonezilla, Mondo Rescue.

We can also take backup through command line. Some of the method are given below:-

Method 1 :- We can use ‘dd’ from Command mode

example : – If you want to backup entire hard disk (sda) –

If you want to create a image of  hard disk –

If you want to restore from your hard disk image –

If you want to create a ISO file –

where, bs = block size

Method 2 :- We also use “rsync” to take backup. rsync first copy all files and directory. and next time it copy only updated files and directory.