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Re: using dump?



 Hi, Scott. 


If you used "mt rewind", that would just rewinds the tape, 
and then it would get overwritten. I specified "mt rewoffl", 
which rewinds and ejects the tape. Then you insert the next 
tape for the next day's backups. So the first tape doesn't get 
overwritten unless you reinsert the same tape. 

In a real-world situation, you'd actually use a tape library, 
which would hold multiple tapes, and the mtx command 
to tell the tape library to grab the ejected tape and insert 
the next tape. Then you'd only change the tapes once a week 
(for a 7-tape library) or once a month (for a 30-tape library). 



Scott Ehrlich wrote: 
> Hi John: 
> 
> I'm not sure your response answered what I was looking for... 
> 
> If I am dumping files for backup, why would I want to rewind the tape 
> to be overwritten (I assume they'd be overwritten when performing the 
> next scheduled dump), or is dump smart enough to forward past the 
> written data and not overwrite it, unless, of course, I used /dev/st0, 
> which _would_ overwrite? 
> 
> Thanks. 
> 
> Scott 
> 
> On Thu, 20 Dec 2007, John Abreau wrote: 
> 
>> 
>> 
>> Scott Ehrlich wrote: 
>>> Clarification request - why rewind the tape after all dumps have 
>>> completed?  Wouldn't that be the same as using /dev/st0?  If not, 
>>> what's the difference? 
>>> 
>>> Thanks. 
>>> 
>>> Scott 
>> 
>> If you're doing 10 dumps to the tape, you could use nst0 for the first 9 
>> and then use st0 for the 10th.  But that's less elegant, as seen below: 
>> 
>>    #! /bin/sh 
>> 
>>    export TAPE=/dev/nst0 
>>    for fs in /foo /bar /baz ; do 
>>        dump -0 $fs 
>>    done 
>>    mt rewoffl 
>> 
>> vs 
>> 
>>    #! /bin/sh 
>> 
>>    export TAPE=/dev/nst0 
>>    for fs in /foo /bar ; do 
>>        dump -0 $fs 
>>    done 
>>    dump -0 -f /dev/st0 /baz 
>> 
>> If you want to add /zoidberg to the list, and you have scripts with 
>> dependencies on the order that the filesystems appear on the tapes, 
>> then /zoidberg needs to be dumped after /baz. In the first case, 
>> you could add it to the for... line, after /baz; in the latter, you'd 
>> have 
>> to move /baz to the for... line, and replace /baz in the final dump 
>> line. 
>> That's more complicated and error-prone. 
>> 
>> 
>> -- 
>> John Abreau 
>> IT Manager 
>> Zuken USA 
>> 238 Littleton Rd., Suite 100 
>> Westford, MA 01886 
>> T: 978-392-1777            F: 978-692-4725 
>> M: 978-764-8934 
>> E: [hidden email]  W: www.zuken.com 
>> 
>> 


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