jmsellens@watdragon.waterloo.edu (John M. Sellens) (10/20/87)
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I've been trying to read some TK50 dump tapes I wrote under Ultrix
1.2 with the 4.3 dump using a blocksize of 126. Under Ultrix 2.0,
it seems that dd has trouble with large block sizes, at least on
my sort of weird system. It won't read in the dump tape I have
using an input block size of 126k. After experimenting a while,
it seems that dd may have some problems. For example:
% ls -l a
-rw-r--r-- 1 root 1024000 Oct 17 00:41 a
% mt -f /dev/rmt0h rewind
% dd obs=100k of=/dev/rmt0h <a
write: Error 0
200+0 records in
0+0 records out
Exit 255 ./dd obs=100k of=/dev/rmt0h < a
%
(Lovely error message isn't it? Doesn't even tell you it's from dd.)
Does this happen to anyone else? Or have I broken my system?
This is on a VAXstation II/GPX with a TK50.
John Sellens -- Logic Programming and Artificial Intelligence Group
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jmsellens@dragon.waterloo.{edu,CDN} jsellens@watmta.BITNET
jmsellens%dragon@waterloo.csnetbarnett@steinmetz.UUCP (Bruce G Barnett) (10/23/87)
Reply-Path: In article <9966@felix.UUCP> jmsellens@watdragon.waterloo.edu (John M. Sellens) writes: |I've been trying to read some TK50 dump tapes I wrote under Ultrix |1.2 with the 4.3 dump using a blocksize of 126. Under Ultrix 2.0, |it seems that dd has trouble with large block sizes | |John Sellens -- Logic Programming and Artificial Intelligence Group I had a similar problem with Ultrix 2.0 I was reading in a tape using dd and the following command dd ibs=2048 conv=unblock if=/dev/rmt0 of=file.out The files were corrupted. Actually, every character after 2048 was zero. I read the new man page on dd and tried: dd ibs=2048 conv=unblock rbuf=0 if=/dev/rmt0l of=file.out ------ - The new version of dd uses a read buffer default value of 8. Changing it to 0 seemed to fix the problem. -- Bruce G. Barnett <barnett@ge-crd.ARPA> <barnett@steinmetz.UUCP> uunet!steinmetz!barnett
davids@iscuva.iscs.com (David Schmidt) (10/23/87)
Reply-Path: In article <9966@felix.UUCP> jmsellens@watdragon.waterloo.edu (John M. Sellens) writes: >I've been trying to read some TK50 dump tapes I wrote under Ultrix >1.2 with the 4.3 dump using a blocksize of 126. Under Ultrix 2.0, >it seems that dd has trouble with large block sizes, at least on >my sort of weird system. It won't read in the dump tape I have >using an input block size of 126k. After experimenting a while, >it seems that dd may have some problems. For example: > >[...] > >John Sellens -- Logic Programming and Artificial Intelligence Group I had the same problem. When re-reading the Ultrix 2.0 release notes I found: Paragraph 2.2.5.2, page 2-25, binder 3A (System Manager, release notes) THE DD COMMAND RESTRICTIONS Do not specify a blocksize greater than (64K minus 1) bytes when using the dd command or TMSCP devices may hang. If you want to read the tape you will have to read it under Ultrix 1.2 and then re-write it with a blocksize <= 127. (We had some machines running both versions so we were able to convert our few tapes with the large block size) -- David Schmidt UUCP: davids@iscuva.ISCS.COM ISC Systems Corporation (uunet!iscuva!davids) East 22425 Appleway Phone: +1 509 927-5479 Liberty Lake, WA 99019