small question about tape-based dumps

[Jerry McAllister]

On Sat, Oct 17, 2009 at 08:09:22PM -0600, Tim Judd wrote:

> On 10/17/09, Stevan Tiefert <stevan-tiefert at kabelmail.de> wrote:
> > Am Samstag, den 17.10.2009, 18:49 -0600 schrieb Tim Judd:
> >> On 10/17/09, Jerry McAllister <jerrymc at msu.edu> wrote:
> >> <snip>
> >>
> >> > You do not need to. dump alrady writes that when it finishes each time.
> >> > If you to that, you will get a second one at that location.
> >> >
> >> > You do not need to do the rewind and mt fsf between each dump.  I just
> >> > do it to make it very clear to myself in my scripts what I am expecting
> >> > and that I am doing it right.
> >> >
> >> > ////jerry
> >>
> >> <snip>
> >>
> >> If dump is the tool for tapes, and tar is named after tape archives...
> >
> > Please, no flamewar!!!
> 
> Wasn't planning on starting one.  Sorry if it came across that way.
> 
> >
> >> Do both of these utilities write the *proper* EOF to whatever medium
> >> it's writing to?
> >
> > They both write EOF.
> >
> >> I bring this up, because dump can also write to a file on a formatted
> >> FS.  Does the file end with this same EOF?  What does tar do?
> >
> > There is only one EOF: The EOF.
> >
> >
> >> Why have a mt weof function if it's useless?  I'm loosing the logic in
> >> this one, trying to make sure things work as they should.  I admit
> >> tapes on bsd are so foreign to me, I might as well be speaking
> >> $another-language.
> >
> > weof is not useless. There are some file operations without writing an
> > EOF, like streams or something like that, but tar and dump are writing
> > with an EOF at the end of files :-)
> 
> 
> So it's a item for "good measure" rather than an item "as necessity"
> in creating backups.

Not a good measure.  It would do something different from what
you expect.   You might get 2 EOF-s in a row and the system think
you have two files - one with stuff and one empty one.

////jerry

 
> 
> Thanks for all the info.  I'm happy knowing more.
> 
> 
> --Tim
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