LiveCD’s and MD5SUMS – A Tutorial

don — Sun, 08 Nov 2009 17:52:28 +0000

Fedora 12 is scheduled for release on November 17. I will download the .iso file and the associated md5sum. I’ll take it for a spin and most likely will write my thoughts on it. I will not again make the very foolish error that I did a few days with another livecd. I burned that CD and DID NOT check the md5sum. After all, it’s been awhile since I burned any ‘coasters’. Murphy’s law. I burned a coaster and did not know it. I popped the CD into my drive and rebooted. There were a slew of I/O error messages and a crash. What now? I rebooted again, but into the BIOS setup. There, I changed the first boot device back to the hard disk and completed the boot into a working OS. I could now eject the defective disk from the command line (“eject”).

All of the trouble could have been avoided simply by checking the md5sum. Both K3b and Brasero have built-in tools to do this and while both are reliable burners, either will produce a defective disk from time to time. That is why most distros provide md5sums. They help you to avoid grief.

To be honest, I usually do not have the built-in checking enabled. I prefer to use the command utility md5sum twice as follows:
(1) Bring up a terminal.
(2) Navigate to the directory containing the downloaded .iso file.
(3) Enter “md5sum myfile.iso”, substituting your filename for myfile.
(4) Compare the result to the published md5sum to verify your image.
(5) Exit the terminal and burn the CD with your favorite burning tool.
(6) Insert the CD in your drive. DO NOT reboot.
(7) Bring up a terminal again.
(8) Enter “md5sum /dev/cdrom”
(9) Compare the result to the published md5sum to verify your burn.
(10) Repeat as necessary if either verification fails.

The procedure works well with Ubuntu. You may have to vary the syntax in step (8) for other distros.

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LiveCD’s and MD5SUMS – A Tutorial