我正在尝试将系统从 Ubuntu 11.04 升级到最新支持的版本。与通常使用 Linux 时一样，我遇到了很多乐趣。我找到了一个建议重新映射软件源的答案到不同的位置。
重新映射后，一些条目保持不变，现在引起了问题：
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
deb http://archive.canonical.com/ubuntu maverick partner
deb-src http://archive.canonical.com/ubuntu maverick partner
## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu maverick main
deb-src http://extras.ubuntu.com/ubuntu maverick main
我也需要重新映射它们。这是我在升级失败之前升级时看到的内容：
W:Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/main/source/Sources.gz 404 Not Found
, W:Failed to fetch http://extras.ubuntu.com/ubuntu/dists/natty/main/binary-i386/Packages.gz 404 Not Found
, E:Some index files failed to download, they have been ignored, or old ones used instead.
那么旧版本该服务器的版本？