我使用的是 14.09 版 Ubuntu。当我将系统更新到 16.04 版时，出现错误
更新过程中出现问题。这通常是某种网络问题，请检查您的网络连接并重试。
但是我的连接很稳定，而且我正在使用主服务器，那么问题可能是什么呢？
W:Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/restricted/binary-arm64/Packages 404 Not Found [IP: 91.189.88.162 80]
W:Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/universe/binary-arm64/Packages 404 Not Found [IP: 91.189.88.162 80]
W:Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/main/binary-arm64/Packages 404 Not Found [IP: 91.189.88.162 80]
W:Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/multiverse/binary-arm64/Packages 404 Not Found [IP: 91.189.88.162 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/main/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/restricted/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/universe/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/multiverse/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-backports/main/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-backports/restricted/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-backports/universe/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-backports/multiverse/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/restricted/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/universe/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/multiverse/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-proposed/universe/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-proposed/restricted/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-proposed/main/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
W:Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-proposed/multiverse/binary-arm64/Packages 404 Not Found [IP: 91.189.88.149 80]
E:Some index files failed to download. They have been ignored, or old ones used instead.
答案1
您的 Ubuntu 版本是 14.04 还是 14.10？您的问题表明您正在尝试升级 Ubuntu 14.09。Ubuntu 仅允许您在将 LTS 升级到 LTS（14.04 到 16.04）时跳过中间版本。如果您从 14.10（不再受支持）升级，则需要升级到 15.04，然后是 15.10，然后是 16.04。如果是这种情况，只需全新安装 16.04 会更简单。