sudo apt-get update not working [duplicate]

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 ??

Solution 1:

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