How does one check / verify the md5sum of a disk *after* the iso is burned to the CD?
Elton
On Fri, 2003-09-26 at 00:05, Elton Woo wrote:
How does one check / verify the md5sum of a disk *after* the iso is burned to the CD?
Elton
Assuming the first disk boots properly, when you see the boot: prompt, type:
boot: linux mediacheck
It will check the disk for you (an md5sum is implanted in each disk) and it will tell you if any or all the disks are good.
make an iso of the CD again and do a md5sum name of new iso ?. usually tho, when you download the iso is where you get the problem, so just check the md5sum of the iso you downloaded to the MD5SUM of the files they gave you.
On Thu, 2003-09-25 at 23:05, Elton Woo wrote:
How does one check / verify the md5sum of a disk *after* the iso is burned to the CD?
Elton
On September 26, 2003 12:12 am, Vidyut Luther Vidyut Luther vid@linuxpowered.com wrote:
make an iso of the CD again and do a md5sum name of new iso ?. usually tho, when you download the iso is where you get the problem, so just check the md5sum of the iso you downloaded to the MD5SUM of the files they gave you.
I always run "md5sum *.iso" before burning the disk. What I meant, was "is there a command to run against the finished disk, before proceeding to install (or boot the disk)?"
But I guess I can do as Chris Kloiber suggested and do it after booting.
Elton ;-)
On Fri, 26 Sep 2003, Elton Woo wrote:
On September 26, 2003 12:12 am, Vidyut Luther Vidyut Luther vid@linuxpowered.com wrote:
make an iso of the CD again and do a md5sum name of new iso ?. usually tho, when you download the iso is where you get the problem, so just check the md5sum of the iso you downloaded to the MD5SUM of the files they gave you.
I always run "md5sum *.iso" before burning the disk. What I meant, was "is there a command to run against the finished disk, before proceeding to install (or boot the disk)?"
But I guess I can do as Chris Kloiber suggested and do it after booting.
"md5sum /dev/cdrom" The problem with that is that it is possible for it to fail and the cd still be good or so I am told. I always burn in DAO mode and have never had problems with the above command failing.
HTH,
On 2003-09-26 at 07:36, Tom Diehl wrote:
"md5sum /dev/cdrom" The problem with that is that it is possible for it to fail and the cd still be good or so I am told.
That won't usually work, md5sum will try to read past end of the disc, generate an error and give you wrong checksum.
You have to read exactly right amount of data, isosize will give the size of iso9660 filesystem on disc:
dd count=$[`isosize /dev/cdrom`/2048] bs=2048 if=/dev/cdrom | md5sum -
(2048 is the block size on cdrom.)
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
On Fri, 26 Sep 2003 11:56:56 +0300, Mikko Paananen wrote:
On 2003-09-26 at 07:36, Tom Diehl wrote:
"md5sum /dev/cdrom" The problem with that is that it is possible for it to fail and the cd still be good or so I am told.
That won't usually work, md5sum will try to read past end of the disc, generate an error and give you wrong checksum.
No. It won't, because Tom mentioned DAO mode (Disk-At-Once) where you don't get any run-out sectors at the end of the CD. I think in cdrecord 2.0, it's called SAO mode (Session-At-Once).
You have to read exactly right amount of data, isosize will give the size of iso9660 filesystem on disc:
dd count=$[`isosize /dev/cdrom`/2048] bs=2048 if=/dev/cdrom | md5sum -
(2048 is the block size on cdrom.)
There's also the "readcd" utility to read an ISO image.
- -- Michael, who doesn't reply to top posts and complete quotes anymore.
Hello Tom,
"md5sum /dev/cdrom"
Never realized it could be as easy as that :). I usually do a dd if=/dev/cdrom | md5sum . Difference when using dd is that you could also specify a bs and count which will avoid errors about sectors not found at the end of the disk.
The problem with that is that it is possible for it to fail and the cd still be good or so I am told.
Why would that be? Were you told that as well? The above mentioned errors should not cause md5sum to produce a wrong result.
Bye, Leonard.
-- How clean is a war when you shoot around nukelar waste? Stop the use of depleted uranium ammo! End all weapons of mass destruction.
On Fri, 26 Sep 2003, Leonard den Ottolander wrote:
Hello Tom,
"md5sum /dev/cdrom"
The problem with that is that it is possible for it to fail and the cd still be good or so I am told.
Why would that be? Were you told that as well? The above mentioned errors should not cause md5sum to produce a wrong result.
i'm pretty sure i have had perfectly good CDs produce a bad MD5 sum when running the above command. note -- i didn't say their ISO image files would produce a bad MD5 sum, just running "md5sum" against the burned CD in the drive.
is it possible that there would be extraneous junk at the tail end of the CD that would throw off the checksum?
rday
Hello Robert,
"md5sum /dev/cdrom"
i'm pretty sure i have had perfectly good CDs produce a bad MD5 sum when running the above command.
is it possible that there would be extraneous junk at the tail end of the CD that would throw off the checksum?
Maybe the error output also gets used in the checksum generation. As said, I use dd | md5sum for this. In that case I get correct checksums even if I do not specify a bs and count and see I/O errors. Probably because the error output does not get piped to md5sum.
Ok, I did a test of md5sum /dev/cdrom[1] on both my cd-player and cd- writer. I get a correct result with the writer, and no result due to an I/O error with the player (ie it chokes at the end of the disk, dd with no count works fine).
Bye, Leonard.
-- How clean is a war when you shoot around nukelar waste? Stop the use of depleted uranium ammo! End all weapons of mass destruction.
On Fri, 26 Sep 2003, Leonard den Ottolander wrote:
Hello Tom,
"md5sum /dev/cdrom"
Never realized it could be as easy as that :). I usually do a dd if=/dev/cdrom | md5sum . Difference when using dd is that you could also specify a bs and count which will avoid errors about sectors not found at the end of the disk.
The problem with that is that it is possible for it to fail and the cd still be good or so I am told.
Why would that be? Were you told that as well? The above mentioned errors should not cause md5sum to produce a wrong result.
The image is good but the cd has garbage on the back end. It is one of those things that if the md5sum is good than all is well if it is bad then it might still be good. :-)
HTH,
On Fri, 26 Sep 2003, Tom Diehl wrote:
The image is good but the cd has garbage on the back end. It is one of those things that if the md5sum is good than all is well if it is bad then it might still be good. :-)
i think the trick is to checksum the ISO image as a file if you can, before you burn it to CD.
rday
On September 26, 2003 12:40 pm, Robert P. J. Day "Robert P. J. Day" rpjday@mindspring.com wrote:
i think the trick is to checksum the ISO image as a file if you can, before you burn it to CD.
I *always* run md5sum against the ISOs before burning. If they fail, I *don't* waste my time burning the CD, but I do another download. My question was HOWTO verify the CD *after* it is burnt, but *before* booting it into install mode.
Elton ;-)
On Sep 26, 2003, Elton Woo elwoo@videotron.ca wrote:
"is there a command to run against the finished disk, before proceeding to install (or boot the disk)?"
/usr/lib/anaconda-runtime/checkisomd5
On September 26, 2003 12:40 am, Alexandre Oliva Alexandre Oliva aoliva@redhat.com wrote:
"is there a command to run against the finished disk, before proceeding to install (or boot the disk)?"
/usr/lib/anaconda-runtime/checkisomd5
However, I don't have anaconda-runtime installed ...
Elton ;-)
-
Alexandre Oliva -
Chris Kloiber -
Elton Woo -
Leonard den Ottolander -
Michael Schwendt -
Mikko Paananen -
Robert P. J. Day -
Tom Diehl -
Vidyut Luther