How to backup more than one time on same tape using DLT tape?

hocheetiong · 01-29-2008, 06:53 PM

Hi, I am have a DLT tape drive is 20/40GB model,than at /dev/st0. Now attach to my redhat enterprise linux system.

First time i am backup a folder /home to DLT tape:
# tar -cvf /dev/st0 /home

than ok, all file inside /home directory have been backup, i have try to check on command # tar -tvf /dev/st0.

I want to backup another directory is /etc on the same DLT tape just now, than i using same command # tar -cvf /dev/st0 /etc ,than all file show are backup. But when i want to check all my backup using command # tar -tvf /dev/st0 why just only show me the latest backup "/etc" file, than my previous backup file "/home" not show at all??

Is it my method to backup 2 or more time and continue backup at same tape are wrong?

In RHEL5 is it have any easy method(GUI) software to manage backup? is it Amanda?

Thank you for answer my question.

michaelk · 01-29-2008, 07:07 PM

The device /dev/st0 will rewind the tape when the current operation is complete.
The device /dev/nst0 will not rewind the tape when the current operation is complete.

Therefore when the first backup of your /home completes the tape rewinds and the second backup i.e /etc overwrites the first. Using /dev/nst0 will not cause the rewind to tape.

bigrigdriver · 01-29-2008, 07:37 PM

You could also use tar to *append" /etc to the /home archive.

A quick look at man tar, and a bit of reseach into DLT drives, and it seems to me that you could do:

Code:

tar -cvf /dev/st0 /home

to begin the archive, then

Code:

tar -rvf /dev/st0 /etc

to append /etc to the /home archive. It will take a while longer than michaelk's suggestion because the tape will have to unwind to the end of /home before writing /etc to the archive.

choogendyk · 01-30-2008, 06:54 AM

Following up on michaelk's post, use /dev/nst0 as the device. Then when you tar a directory or partition to the tape it will be left positioned at the end. You can then tar another to the same tape and have two tape files. Continue until you hit the end of the tape (if you do).

To find out what's up with the tape, use the mt command. `mt -f /dev/nst0 status` will tell you where it is positioned. `mt -f /dev/nst0 rewind` or `mt -f /dev/nst0 fsf 1` etc. allow you to rewind or reposition the tape.

Of course, you could use Amanda to manage your backups. It might be overkill for just one machine, but then you would have learned a new tool. It is not GUI based, but it is very straightforward from the command line.