I cannot upgrade my ubuntu from 13.04 to 13.10
This is error while i try to upgrade:
W: GPG error: http://download.opensuse.org Release: The following signatures were invalid: KEYEXPIRED 1386276565 W: Failed to fetch http://th.archive.ubuntu.com/ubuntu/dists/natty-backports/main/source/Sources 404 Not Found W: Failed to fetch http://th.archive.ubuntu.com/ubuntu/dists/natty-backports/restricted/source/Sources 404 Not Found W: Failed to fetch http://th.archive.ubuntu.com/ubuntu/dists/natty-backports/universe/source/Sources 404 Not Found W: Failed to fetch http://th.archive.ubuntu.com/ubuntu/dists/natty-backports/multiverse/source/Sources 404 Not Found E: Some index files failed to download. They have been ignored, or old ones used instead.
What have i tried already?
- Unchecked something like ..from CD-ROM.. on Ubuntu Software Center > Software Source.
- Tried to use this command "sudo rm -rf /var/lib/apt/lists/*"
- Tried to change download server
How can i solve this problem?