I have made tar archive of my system.. How can I make that tar archive to be bootable.. simply to install new linux from the archived tar file.. thanks in advance
If I understand this correctly, you made a tarball of everything under /, and want to restore the contents of your tarball to a new system?
sun2ecliptic yes u are right 
I have made tarbal of /
Tar archives are not actually bootable. Really, there isn't any sort of way to boot from that. What you could with a tar archive would be use a rescue mode linux session to re-partition your hard disk, and then extract the contents of your tar archive (consider it similar to a zip file), to the filesystem while it is mounted.
Are you simply looking for a good way of recovering in the event of disaster? I'd recommend making use of r1soft's CDP platform. Some information about that can be found at r1soft.com.
You're really only left with one option for restoring from tarball, aside from going into rescue mode. First, put the tarball on some sort of removable media (likely an external USB hard drive, given the size). Second, do a fresh install on the system in question. Mount the external media with the tarball. Extract the usual configuration directories (/etc/, /usr/local/, /opt, /var/lib) and /home, after installing the software required.
Hypothetically, you could uncompress the tarball somewhere else and do a straight dd or block level copy, but I have my doubts that would work unless you manipulated the boot loader after, to agree with the uncompressed kernel and content. I agree with ahyes, the bigger picture is coming up with a better backup method. You can backup with tar, but using tar to backup is really more of a supplemental solution to configurations, databases, home directories - not binaries. You're best bet, if using tar to backup everything important, is to create a kickstart image. That way, if you need to restore, you simply run the kickstart and extract your tar.
Thanks Dear friends for your reply! Well I think if a disaster happens and if I untar tarbal archive to newly installed system and rewrite archive to / it will be completly restored.. Am i not right?
mark54g Mondo rescue seems quite nice... thanks any way bit I have already made backup using tar thanks to all
No problem. I just thought that looking forward it may be a better solution