Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!ndcheg!ndmath!mahesh
From: mahesh@ndmath.UUCP (Mahesh)
Newsgroups: comp.unix.questions
Subject: Tape doesn't rewind after backing up with 'tar'
Keywords: tar,backup,rmt8
Message-ID: <1325@ndmath.UUCP>
Date: 6 Mar 89 14:31:36 GMT
Distribution: usa
Organization: Math. Dept., Univ. of Notre Dame
Lines: 34

This is really perplexing, and I know I should know the answer, but,
somehow I can't seem to figure out the answer.  Problem is ==>

  When I back up tapes to the device /dev/rmt8, after the files are
  written to the tape, the tape rewinds.  On the other hand, if I wrote
  to /dev/mt8, the tape would not rewind after the write.  The manual
  says

  " The mt files are useful when it is desired to access the tape in a
  way compatible with ordinary files.  When foreign tapes are to be
  dealt with, and especially when long records are to be read or
  written, the 'raw' interface is appropriate. "

  Further, the manual goes on to mention that the files mt8...mt11 are
  rewound when closed.

This brings me back to the original questions:

1) What is the difference between mt8 and rmt8 (in simple english)
2) Why does the tape rewind after 'tar'ing to rmt8 and not after
'tar'ing to mt8
3) What does the phrase "compatible with ordinary files" mean in
paragraph three above?

The system I have is a convex running BSD 4.2, and I'm doing a standard
'tar' at 1600 bpi.

Thanx in advance for any help you can provide

Mahesh Subramanya
mahesh@darwin.cc.nd.edu
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