Hi there.
First, you need to download the correct iso file. Try from here:
http://www.releases.ubuntu.com/13.10/
You will then need to change directory (cd command) to the directory (AKA folder) that contains the downloaded iso.
Ubuntu is case sensitive, so downloads & Downloads are two different places.
Then run the md5 or sha256 command, for example:
Code:
md5sum ubuntu-13.10-desktop-i386.iso
Or whichever version you have downloaded.
The result will be a string of characters that should match the string for your downloaded version from this page:
https://help.ubuntu.com/community/UbuntuHashes
If the bunch of characters don't match download the iso again.
This all assumes you have a working Ubuntu installation to do this from.
Good luck.
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