small question about tape-based dumps
Tim Judd
tajudd at gmail.com
Sat Oct 17 02:43:27 UTC 2009
Replies inline
On 10/16/09, Jerry McAllister <jerrymc at msu.edu> wrote:
> On Fri, Oct 16, 2009 at 11:13:21PM +0200, Stevan Tiefert wrote:
>
>> Hello list,
>>
>> one example: If I have three partitions and I want to backup every day
>> these partitions, will I need 21 tapes?
>>
>> I ask because it seems it is not possible to place more than one dump on
>> one tape, isn't it?
>
> You can easily put more than one dump on a tape if there is
> room enough for them. Check out the mt(1) command.
>
> Something like mt fsf 1 will skip over the first dump file
> so you can write the second. mt fsf 2 will skip over two files, etc.
> That is dump files, not files within the dump. Each dump of a
> filesystem is one file.
>
> If you need to restore, it is just the same. The first dump is
> the first file. The second dump is reached by skipping 1 file
> with the mt command, etc.
>
> I actually rewind and skip between each dump of multiples made
> to the same tape. I also use the no-rewind device for the tape.
>
> So first dump is: dump 0af /dev/nsa0 /
I understand that this creates a dumpfile on nsa0, and as I understand
tapes (which may be wrong, which I ask for clarification here).. To
mark a end-of-file to be able to fast-forward/rewind, why can't you
use:
mt -f /dev/nsa0 weof
It's description in mt(1) says it writes the end-of-file mark at
current position
> For second dump: mt -f /dev/nsa0 rewind
> mt -f /dev/nsa0 fsf 1
> dump 0af /dev/nsa0 /usr
So if we use weof, would the 2nd dump then be:
dump 0af /dev/nsa0 /usr
mt -f /dev/nsa0 weof
> third mt -f /dev/nsa0 rewind
> mt -f /dev/nsa0 fsf 2
> dump 0af /dev/nsa0 /var
And 3rd:
dump 0af /dev/nsa0 /var
mt -f /dev/nsa0 weof
> etc.
>
> when all done mt -f /dev/nsa0 rewind
> mt -f /dev/nsa0 offline
And I've never used offline, guess I'll start now.
> I have this all in a script that also writes an index file
> as the first file on the tape.
>
> Of course if you are doing a change dump the dump command is
> going to look more like:
>
> dump 1af /dev/nsa0
> etc.
>
> ////jerry
>
>>
>> With regards
>> Stevan Tiefert
Thanks for any input!
--TJ
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