Marek Pawinski wrote:
I picked this up, i don't know if it pertains to the issue:
Bad Md5sums? (maybe not)
Just burned a CD from an ISO image and the md5sum doesn't match?
The CD may be just fine... what you may be experiencing is padding which alters the md5sum. Before throwing away the CD and cursing, try this:
cmp /dev/cdrom ISO_image
For example, I got a bad md5sum from my 9.2beta1 CD1:
$ dd if=/dev/cdrom | md5sum 1333216+0 records in 1333216+0 records out e82309091ad6b44a1218dc6f33c3b058 -
It should be: 7a0479dc917d35bd822cecb558c8d432
So, I tried:
$ cmp /dev/cdrom /ISO/Mandrake/MandrakeLinux-9.2beta1-CD1.i586.iso cmp: EOF on /ISO/Mandrake/MandrakeLinux-9.2beta1-CD1.i586.iso
The EOF on the ISO image means that the CD image is an EXACT copy PLUS padding. An EOF on /mnt/cdrom would have meant the CD was incomplete.
Just to prove the CD was really OK, I issued this piped string of commands:
$ dd if=/dev/cdrom | head -c 682575872 | md5sum 1333162+0 records in 1333161+0 records out 7a0479dc917d35bd822cecb558c8d432 -
Got the correct md5sum... :^) BTW, 682575872 is simply the length of that particular ISO image.
So, more generically, we can use this pipe stream:
dd if=/dev/cdrom | head -c `stat --format=%s ISO_image` | md5sum
i.e.,
$ dd if=/dev/cdrom | head -c `stat --format=%s /ISO/Mandrake/MandrakeLinux-9.2beta1-CD1.i586.iso` | md5sum
1333162+0 records in
1333161+0 records out
7a0479dc917d35bd822cecb558c8d432 -
For the purists, the size can be passed as an argument to dd like this (not verified):
dd if=/dev/cdrom bs=`stat --format=%s ISO_image` | md5sum
Marek
Hi Marek, I've been giving your CL examples a try today, been a bit busy lately, anyway this is how it worked for me.
cmp /dev/scd0 /mnt/Win-g/disc3.iso cmp: EOF on /mnt/Win-g/disc3.iso
Now this result surprized me. I used cdrecord to create the installation CD I don't remember using any command that would of added padding to the burnt disc. I use -dao almost without exception, nothing else that adds Zero's etc between data tracks. But still this says I did. I just wondered why ? and what would it return if an exact copy ?
then, dd if=/dev/scd0 | head -c 669016064 | md5sum 5ad870e696953f4bbd0a91936873890e - 1306673+0 records in 1306672+0 records out
which agrees with, 5ad870e696953f4bbd0a91936873890e disc3.iso the correct md5sum
I note you can pass the iso file size direct to head CL
OK, so everything looks fine so far.
Now for the problem, dd if=/dev/scd0 bs=`stat --format=%s /mnt/Win-g/disc3.iso` | md5sum 1+1 records in 1+1 records out 526cfebe2c2da7c6e464bed37969e4c9 -
OK, I did something obvious wrong. but what ?
By the way, NICE ! I like it.
John
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