Date: Sun, 23 May 2010 16:23:08 -0700 From: Doug Hardie <bc979@lafn.org> To: Manolis Kiagias <sonicy@otenet.gr> Cc: freebsd-questions - <freebsd-questions@freebsd.org> Subject: Re: Verifying a DVD Message-ID: <BB2CB2B0-942C-4510-990E-BAC7D92540D1@lafn.org> In-Reply-To: <4BF9ACDE.6050502@otenet.gr> References: <76E02DE6-9A61-4D24-9638-ABB7418711D9@lafn.org> <4BF9ACDE.6050502@otenet.gr>
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On 23 May 2010, at 15:31, Manolis Kiagias wrote: > On 24/05/2010 1:23 =CF=80.=CE=BC., Doug Hardie wrote: >> I am periodically backing up a bunch of files to DVD. I use mkisofs = to create the original image and growisofs to write it to a real DVD. = However, at that point I want to verify that the write was successful. = I tried using dd to read back in the DVD to a file. Its interesting = that the bs parameter must be at least 2048 or dd complains about a = parameter error. However, the big issues is that the original image = file is shorter than the read file. The difference is 10240 bytes. = This difference is the same for bs 2048, 10240, or 102400. It appears = that dd is adding one last block. Is there a way to prevent this or = remove that block? >>=20 >=20 > Use the count=3D parameter in dd to read the exact count of blocks in = the > DVD. Use isoinfo to obtain this information from the media itself. = Have > a look at the instructions here: >=20 > http://www.troubleshooters.com/linux/coasterless.htm >=20 >=20 Thanks. That works great. I did discover that appending 10240 zeros to = the end of the original iso file also works. However, I am not = convinced that it will always be that value. The approach above should = be more reliable.=
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