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Operating System - Tru64 Unix
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help regarding tape backup

Jessica P
Regular Advisor

help regarding tape backup

Hi

I am presently taking backup of my data (about 14 gb) on tru64 using the command
tar cvf /dev/nrmt0h .
The tape i am using has capacity of 24 gb.now plz suggest me how can i reuse the same tape and start writing from the first sector itself ie i want to erase the previous data and use the tape again and again
also what is the differnce b/w tar rmt and nrmt


also how can i see the contents of the my tape

plz suggest

thanks
jessica
6 REPLIES
Vladimir Fabecic
Honored Contributor

Re: help regarding tape backup

Hello
nrmt is "non rewind" tape, and rmt is "rewind" tape. That means, if you use:
# tar cvf /dev/nrmt0h .
you use "no rewind" tape and you can write to available tape space with another tar cvf command.
If you use:
# tar cvf /dev/rmt0h .
tape will rewind after backup is completed.
If you use second option, you will overwrite previous data.
So use # tar cvf /dev/rmt0h .
and you will use tape from beginning again and again.
See man tar.
To see the contents of the tape:
# tar tvf /dev/rmt0h
In vino veritas, in VMS cluster
Mulgund
Frequent Advisor

Re: help regarding tape backup

I am assuming you are using a v51b system connected to the tape drive.

0. Difference b/w rmt and nrmt: using rmt, tape drive will rewind after completion of dump/restore. nrmt will just leave the tape head beyond the dumped/restored block without rewinding the tape. rmt and nrmt are v4.x ver . device naming, /dev/tape and /dev/ntape are v5.x ver. device naming.


1. How to see the current tape contents.
As root,
# mt -f /dev/ntape/tape0_d1 online

/* the above command will rewing the tape and place the tape head on top of the first recorded media block.*/

#tar tvf /dev/ntape/tape0_d1 |more

/* the above command will list the contents as in 'ls' command o/p. */

2. To reuse the tape.

#mt -f /dev/ntape/tape0 online
/* this will rewind */

#tar cvf /dev/ntape/tape0_d1

/* this will overwrite the existing data on the tape. You need not specifically erase the current tape content.

Hope this helps.

-Srinivas
Vladimir Fabecic
Honored Contributor

Re: help regarding tape backup

Mulgund
/dev/nrmt0h means it is TRU64 v4.0x, not v5.x.
Regards
In vino veritas, in VMS cluster
Mulgund
Frequent Advisor

Re: help regarding tape backup

Right, I said the same,

>> rmt and nrmt are v4.x ver . device naming, /dev/tape and /dev/ntape are v5.x ver. device naming.

I meant /dev/rmt and /dev/nrmt only

-Srinivas
Michael Schulte zur Sur
Honored Contributor

Re: help regarding tape backup

Hi Jessica,

does this mean you do not remove the tape after a backup?

greetings,

Michael
Ivan Ferreira
Honored Contributor

Re: help regarding tape backup

You are using the no rewind device, /dev/nrmt0h, if you want to overwrite the data, use the rewind device:

tar cvf /dev/rmt0h .

This will rewind the tape and start writing from the beginin overwriting all again.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?