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LiveCD’s and MD5SUMS – A Tutorial 1

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.

One comment on “LiveCD’s and MD5SUMS – A Tutorial

  1. Reply stlouisubntu Nov 8,2009 8:50 pm

    I agree with you and I prefer to use the md5sum command line utility. However, where I differ is that I do not want to have to manually compare md5 sums. Here’s what I do:

    Using your favorite text editor (such as gedit, leafpad, kate?),
    make a one line text file as follows:

    copy and paste full md5sum filename.iso

    and save as .iso.md5 in the same directory as the .iso file
    (also note that there are two spaces between the md5sum and the filename. Then from the command line in the same directory as the .iso file and your new md5sum text file enter

    md5sum -c filenane.iso.md5

    if successfully you get a message of .iso OK

    This eliminates human error in manually comparing md5sums. The most friendly .iso download sites include md5sum text files (so you will not need to make your own.) Ubuntu offers one big text file containing all the md5sums and filename.isos as one big text file from which to copy/cut and paste to easily make your own md5sum text file for the respective .iso you downloaded.

    Hope this helps.

    Cheers.

    (Please delete the first two posts as wordpress kept messing up my posts.)

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