neal@mnopltd.UUCP (02/14/91)
I gleaned the following sort of snippet of script from the i386 group to
make a cpio backup
compress it
increase the blocking to reduce the "shoe-shining" effect
find usr2 -print >> /tmp/bkup.names
cat /tmp/bkup.names | cpio -ocvB | compress | dd ibs=5120 obs=512k > /dev/rct0
However, it seems that dd cannot perform output to the tape drive under any
set of parameters without getting a write error on the last block.
Even:
dd ifs=/tmp/moo ofs=/dev/rct0
will generate a write error and, when copied back, the file will be missing
the last N hundred bytes. (where N depends on the blocking factor)
(BTW: the drive and tape work fine with tar and cpio) The drive is a Wantek
5150pk and I do have the software patch for it. Have I blown my valves
or is there maybe a buglet here?
------------------------------------------------------------------------------
Neal Rhodes MNOP Ltd (404)- 972-5430
President Lilburn (atlanta) GA 30247 Fax: 978-4741
emory!mnopltd!neal
------------------------------------------------------------------------------gene@zeno.mn.org (Gene H. Olson) (03/09/91)
itkin@mrspoc.Transact.COM (Steven M. List) writes: >tar and cpio used fixed size blocks. dd by default writes a partial block >if the last block is not fully sized. In this case it sometimes helps to >use the "conv=sync" option to dd. This forces ALL blocks to be the same >size and will force the last block out to full size. Be careful using conv=sync when dd is fed by a pipe. If for any reason it reads a partial block from the pipe (and there are lots of ways that can happen) it will pad out that block to full size. If that happens in the middle of your archive, you are screwed, and you may not discover it until you really need that archive. Ideally, your data compression program should do the padding for you. The "compact" program I posted to the net some time ago does that automatically. _________________________________________________________________________ __ / ) Gene H. Olson gene@zeno.mn.org / __ _ __ _ (__/ _(/_//_(/_ gene@digibd.com