| Bill Jonas on Sat, 23 Mar 2002 01:00:15 +0100 |
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On Fri, Mar 22, 2002 at 10:18:19AM -0500, epike@isinet.com wrote: > this sounds very cool thanks for posting the info No problem. > if theres a read error does dd at least complain for warning? Yes. In fact, it will abort the whole transfer, with an error message like this: dd: reading `/dev/cdrom': Input/output error Something else I like to do when I want to make sure it transferred exactly is to use cmp to compare, like "cmp /dev/cdrom output-file.iso". On Fri, Mar 22, 2002 at 12:27:29PM -0500, Doug Crompton wrote: > I am not sure. Does dd from a device without limits copy the entire > medium? Yes. It reads until it reaches EOF, which means there's no more data. It would be the same as doing "cat /dev/cdrom >output-file.iso" or "cp /dev/cdrom output-file.iso". The nice thing about dd is that you can specify a block size to speed up the transfer, ie, bs=1M, so that you have fewer read/write operations going on (transfer a meg at a time versus the default block size for the device). You may be thinking of the use of dd to create a file of a certain size, dd'ing from /dev/zero. In this case, bs and count are needed since /dev/zero *never* returns EOF and dd will keep going until your device is full, failing with an error message like "dd: writing `filename': No space left on device". On Fri, Mar 22, 2002 at 01:08:05PM -0500, Fred K Ollinger wrote: > Try it w/ a cd-rw. It works great for me. And I'm the one w/ terrible luck > w/ things. :) Interesting. I seem to almost always get an I/O error when trying to dd a CD-RW that I've written. Maybe it's my burner. I've been wanting to replace it anyway since it's only 4x4x32. Maybe one of those nice new PlexWriter 40/12/40A (PX-W4012TA/SW) models, when I have cash (read: job -- still looking, BTW, if anyone has a lead). ;-) On a related note, I recently burned a CD with FreeBSD's burncd utility. I had FreeBSD booted at the time and wanted to write a small disc, so I thought I'd give that a shot. However, the resulting CD didn't seem to work in my DVD-ROM drive. It was a small bootable image for installing Gentoo, about 17M. DVD-ROM wouldn't read it while the drive I burned it on would, but even that went wonky once while copying data off of it. Anyone know if this would be because of burncd itself? In any event, it was nice not having to jump through hoops messing with SCSI emulation just to get an ATAPI CD-RW drive to work. -- Bill Jonas * bill@billjonas.com * http://www.billjonas.com/ Developer/SysAdmin for hire! See http://www.billjonas.com/resume.html Attachment:
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