Checking your CD / DVD ISO images after downloading . . .


Everyone could have murmured or shouted these words them self while they are facing some problem with installing ISO images. Last week  i downloaded Fedora 12 DVD -3.0 GB. but i got problem with installation due to corrupted media . I spent one day for downloading that iso image , i dont know why this iso image get corrupted .
 any way i tried to find the answer .  Finally i found some tips and tricks with downloading ISO images.


Oops , My Fedora dvd is getting struck .
What the hell is this ? why this DVD is not working  properly ?
Oh my God after 9 hours of downloading , I got problem with DVD .

Reason for corrupted ISO images
  1. Download Interruption or incomplete download – Use proper download manager or accelerator for downloading ISO images.
  2. The ISO image might be corrupted while burning with high speed . So use 2x /4x speed in your burning application to avoid this problem
  3. Forget to check with hash code  – All ISO images comes with some hash code for checking its content . user need to check after download it.
Checking ISO images using SHA1SUM or MD5SUM
The first two problem could be easily solved using download manager and setting burning speed . here some information about checking ISO image has been given for Linux users
  • Download ISO images , For example :  Fedora-12-i386-DVD.iso
  • Download the MD5SUM or SHA1SUM hash keys from fedora website – Save the second line into one text file [check.txt]
Hash: SHA1
f0ad929cd259957e160ea442eb80986b5f01daaffdbcc7e5a1840a666c4447c7 *Fedora-12-i386-DVD.iso
  • Now use sha1sum or md51sum command for checking your ISO image . In terminal type the following command
# sha1sum    -c check.txt
or
# md5sum    -c check.txt
  • If the file has no error then the output of above commands would be
Fedora-12-i386-DVD.iso: OK
  • Else some error message would be displayed .
Note : The format of the checksum file is so important , it has to be like
<checksum value><TWO WHITESPACES><name of file to be checked>
In our case , the check.txt sould have
f0ad929cd259957e160ea442eb80986b5f01daaffdbcc7e5a1840a666c4447c7  Fedora-12-i386-DVD.iso

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