backup problem (media error)

[Janghyegyung]

$ mt -f /dev/rmt0 rewind

$ tar tvf /dev/rmt0.1 (or tar xvf /dev/rmt0.1)
--> rwxrwxrwx 205 0 49 Oct 15 10:20:57 2001 /tmp/myfile

$ backup -u -0 -f /dev/rmt0.1 /myfilesystem
--> ...
...
backup: Media write error 160 blocks into volume 1
backup: MEDIA ERROR!
backup: NEEDS ATTENTION: Do you want to restart?: ("yes" or "no&quot

What's this problem?
Our backup script on unix servers contains the tar -xvf command before the backup command. We replaced the tape device last week and we tried to backup first after that time. All other servers processed backup script like this and no problems.

If

$ tar cvf /dev/rmt0.1 /tmp/myfile instead of tar tvf or tar xvf
$ $ backup -u -0 -f /dev/rmt0.1 /myfilesystem

Then NO problem!!
I don't know what the difference between tar xvf/tvf and tar cvf is.

Help me!

 

[KenCunningham]

tar cvf will write to the tape device or archive, whilst tar xvf will extract data from the tape or archive. Use tar tvf to read what's on the tape or in the archive without writing the data to disk. Further info. is available in the man pages for tar.

Hope this helps.

 

[Janghyegyung]

I know basic tar command, my point is the different backup results after the command tar -cvf/tar -xvf/tar -tvf and media error after the tar -xvf command and tar -tvf command.