Incremental backup is daily backup.Only updated files are backed up.

profile is a file in the users home directory which contains details of user
environment The user working shell, path, mail are few variables which will be
defined in user profile file. The contents in profile works at user level.

egrep is a command that allow you to generate a listing using variables
egrep "First|Last"
this would produce a listing that gave only the data from the file queried that were associated with the variables Firt  and Last.

By following these steps we can recover a system when root password has lost -
-> first come to ok prompt by init 0 command.
-> enter into single user mode  #init -s
-> mount /dev/rdsk/c0t0d0 /a
-> edit shadow file by vi /a/etc/shadow  and  Remove the password
-> change to root directory #cd /
-> unmount the directory #umount /a
-> reboot the system

A filter is a Unix command that do some manipulation of the text of a file. The most powerful and popular Unix filters are sed and awk commands.