Path: utzoo!utgpu!watmath!clyde!att!ucbvax!NUSVM.BITNET!GBOPOLY1
From: GBOPOLY1@NUSVM.BITNET (fclim)
Newsgroups: comp.sys.apollo
Subject: re: getting tar to do what it is told
Message-ID: <8812030651.AA28193@umix.cc.umich.edu>
Date: 3 Dec 88 06:52:44 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 47
X-Unparsable-Date: Sat, 03 Dec 88 14:03:08 SST


     tom cunningham asked how to use tar on cartridge tapes.  the
domain/ix 4.2bsd man page (section 4 on mtio) says that /dev/rct[8|12]
has a block length of 512 bytes and the man page (section 1 on tar)
says that (under the b option) the blocking factor on cartridge tape
must be 1.
     therefore, you must do:
% /com/rbak -dev ct -rewind
% tar cvbf 1 /dev/rct8 ....

note the b option must be given and the arguments 1 and /dev/rct8 must
be in the same order as the b and f options.

you may specify the default blocking factor of 20 only when you are
using /dev/rmt[8|12].  ie
% tar -cv ....
% tar -cvb 20 ...
are the same.  the max arg to the b option on /dev/rmt[8|12] is 20.
note that you need not rewind the mag-tape.  but you must *always* issue
% /com/rbak -dev c -rewind
first before you use tar or dd(1) on the cart tape drive.

     sometimes, i make tapes in another way:
% pdtar cvzf foo.pdtar.Z ...
% /com/rbak -dev ct -rewind
% /com/rwmt -dev ct -raw -unlab -write -rl 512 -bl 512 -rf f -f 1 foo.pdtar.Z

this way, you may have a few tar files on tape by changing the -f 1 option
to /com/rwmt to -f 2, etc.  eg:
% /com/rwmt -dev c -raw -unlab -w -rl 512 -bl 512 -rf f -f 2 bar.pdtar.Z
puts bar.pdtar.Z after foo.pdtar.Z.  When reading this tape on, say, a
sun machine, one may use
% tar -xvf /dev/rct0
where /dev/rct0 on a sun does not rewind when tar finished reading
foo.pdtar.Z.

to read bar.pdtar.Z on an apollo, do
% /com/rwmt -dev c -raw -unlab -r -rl 512 -bf 1 -rf f -f 2 bar.pdtar.:z

     hope this helps.  :-).  fclim.


fclim          --- gbopoly1 % nusvm.bitnet @ cunyvm.cuny.edu
computer centre
singapore polytechnic
dover road
singapore 0513.