Why tar Can Not Back Up All

[Steven Chen_1]

Hi,

I have a script to get tar to backup 3 directories, but only the last directory files are backed up. I wonder why and would like to have some comment.

The codes are like:
--------------------------

#!/bin/sh
cd /disk7/aaa
tar cvf /dev/rmt/c2t0d0BEST /disk7/aaa
#
cd /disk8/bbb
tar cvf /dev/rmt/c2t0d0BEST /disk8/bbb
#
cd /disk3/ccc
tar cvf /dev/rmt/c2t0d0BEST /disk3/ccc
#
#eof
---------------------------------------

So only /disk3/ccc files being backed up. That measn only last line of codes is executed.
Is it strange?

Thanks,

Steven

[Patrick Wallek · Accepted solution]

You must use the no-rewind tape device in order for your backup to work properly. Replace the /dev/rmt/c2t0d0BEST with /dev/rmt/c2t0d0BESTn and your backups will work.

Without the no-rewind device file the tape is getting rewound after each tar session, thus each backup overwrites the previous and you are only left with the last backup.

Do the step above and it will work for you.

[A. Clay Stephenson]

Hi Steven,

This is is easy. Actually all 3 are being backed up but since you are using a rewind device the first two are overwritten each time.
If you will switch to /dev/rmt/c2t0d0BESTn, things will be better.

Regards, Clay

[Kofi ARTHIABAH]

Steven:

In addition to the above, you could do :

tar -cvf /dev/rmt/.... -C /disk7/aaa -C /disk8/bbb -C /disk9/ccc etc.

check:
man tar

good luck

[Steven Chen_1]

Thanks for all the help.

BTW, can someone explain what c2t0b0BESTb and nb means?

Steven

[Patrick Wallek]

The normal device file c?t?d?BEST are AT&T best density
The c?t?d?BESTb are Berkely best density
You add the 'n' c?t?d?BESTn or c?t?d?BESTnb and that makes them no-rewind device files.

As to the difference between AT&T and Berkeley, I'm not sure.

[A. Clay Stephenson]

Hi Steven, Patrick:

You can man mt for a very explanation of the berkeley and AT&T tape behavior.

Clay

[Patrick Wallek]

Thanks for the point in the right direction for AT&T vs. Berkeley, Clay. That does explain it pretty well.

[Bill Hassell]

One additional point: start using the lssf command instead of ls -l or ll for all device files. The names of device files are subject to change so you need a tool to actually decode what the major/minor numbers actually mean.

[Steven Chen_1]

Thanks for the help and I get what I want -- all are tar up.

However, I don't get it is it is still in absolute path that is not what I desire. Otherwise I simply use tar with all directories.

While I cd to proper directory, and have tar to backup, how come I still get absolute path with slash?

Anyway to get a relative path in this case?

[Victor BERRIDGE]

Hi Steve,
In order to backup with tar directories with relative path, once in the directory use . in your tar:
cd /home; tar -cvf {tapedevice} .

It will archive from this directory as ./files...

All the best

Victor

[Curt Thompson]

Hello Steven,

One more option.

Continue to use the same devicefile you have always used before. Instead, use tar with the
'-r' option. This will append a new file to the end of the archive without regard to its current position. This is most helpful if you rewind or eject the tape and then need to add more to it later.

For example:
tar -rvf /dev/rmt/c4d0t0BEST yourfile

Good Luck,
Curt