How to see files backed up on tape using dd command

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Operating Systems Linux Red Hat How to see files backed up on tape using dd command
# 1  
Old 01-31-2011
How to see files backed up on tape using dd command

Hi all,

I need some help...

- I have two servers - serverA and serverB.
- ServerB has a tape drive
- I took a backup of some files on serverB on to tape drive on serverA.
- I used the following command:

serverB> tar cvfb - 20 ./<file> | ssh <serverA> 'dd of=/dev/nst0 bs=20b'

- I repeated the same command for lots of other database files...
- Above works fine and gives no errors
- I went to serverA, which has tape drive, and rewind the tape, using

'mt -f /dev/nst0 rewind' commnd

- Now, I want to see contents on the tape but dont know how Smilie

- I thought tar tvf /dev/nst0 will do the trick but it gives input/output errors - there are no errors when files were copied to the tape.

- I now realise that command used to put files on tape was 'dd' and now I do not know how to display the contents of backup using dd command... I do not want to restore files to see if they backed up OK... I just want to see files are in the tape... I have 6TB of files to check Smilie

Any help from you will be appreciated.

# 2  
Old 01-31-2011
Well, the first thing that strikes me is that you have set a block size in your backup (-b 20) that you have not set on your listing request. It may suggest that it is the deafult, but you never know it might just be that.

The other thing I would worry about is if you are writing to the no-rewind device. If not, then you may auto-rewind at the end of the write and the next will overwrite each time, to you will only have the last backup. It depends on your OS as to which is the non-rewind device. AIX would normally be /dev/rmt0.1, but that doesn't match your format so you would have to look at man rmt - or perhaps man nst in your case to see if it helps.

It may also be that the ssh is getting in the way and you may not be writing a valid archive in the first place. When I have done this sort of thing, I have shared the device as a whole and driven it directly from server B without the piped control.

# 3  
Old 01-31-2011
Hi Robin,

Thanks for a prompt reply.

Everything worked fine, once I found where the problem was Smilie

Instead of using a backup software, I decided to work on the default unix utilities to control the tape library and device - mtx (for controlling the tape library/robotic arm; mt for the dive) and tar to do the backup. In doing so, I mixed the drive letter/number and the slot number from where the tape came from. My tape was in drive 1 and I was trying to read it from drive 0 Smilie .

Now all is fine (tar tvf /dev/nst0 is showing the contents) I am sorry to have taken so much of your's and others' time.

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