This question already has an answer here:

Err http://ppa.launchpad.net utopic/main amd64 Packages                        
  404  Not Found
Get:63 http://in.archive.ubuntu.com utopic/universe Sources [6,736 kB]         
Err http://ppa.launchpad.net utopic/main i386 Packages                         
  404  Not Found

W: Failed to fetch http://ppa.launchpad.net/cdemu/ppa/ubuntu/dists/utopic/main/binary-amd64/Packages  404  Not Found

W: Failed to fetch http://ppa.launchpad.net/cdemu/ppa/ubuntu/dists/utopic/main/binary-i386/Packages  404  Not Found

E: Some index files failed to download. They have been ignored, or old ones used instead.

What to do in this case ??

marked as duplicate by steeldriver, muru, Panther, Eric Carvalho, Elder Geek Feb 17 '15 at 15:28

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.


Follow following steps

  1. First Backup your old sources.list, mv /etc/apt/sources.list /etc/apt/sources.list.back

  2. Check your OS version, Release

    lsb_release -r

  3. Go to http://repogen.simplylinux.ch/

  4. Select Country

  5. Select Ubuntu Release

  6. Select Your choice. Important is first 12 and choose whatever you require

  7. Generate new sources list

  8. Open your editor like vi or vim

    vim /etc/apt/sources.list

  9. Save the file

  10. Retry with sudo apt-get update

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