在VirtualBOx中安装ubuntu系统，将源更换为阿里，网易之类的源都报下面这写错误

E: Failed to fetch http://mirrors.aliyun.com/ubuntu/dists/trusty-backports/main/binary-arm64/Packages  404  Not Found [IP: 36.104.154.185 80]
E: Failed to fetch http://mirrors.aliyun.com/ubuntu/dists/trusty-proposed/main/binary-arm64/Packages  404  Not Found [IP: 36.104.154.185 80]
E: Failed to fetch http://mirrors.aliyun.com/ubuntu/dists/trusty-security/main/binary-arm64/Packages  404  Not Found [IP: 36.104.154.185 80]
E: Failed to fetch http://mirrors.aliyun.com/ubuntu/dists/trusty-updates/main/binary-arm64/Packages  404  Not Found [IP: 36.104.154.185 80]
E: Failed to fetch http://mirrors.aliyun.com/ubuntu/dists/trusty/main/binary-arm64/Packages  404  Not Found [IP: 36.104.154.185 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.

将源改为中国科学技术大学的源之后，就成功了：

$ sudo vim /etc/apt/sources.list

deb http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-backports main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-proposed main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-security main multiverse restricted universe
deb http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-updates main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-backports main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-proposed main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-security main multiverse restricted universe
deb-src http://mirrors.ustc.edu.cn/ubuntu-ports/ xenial-updates main multiverse restricted universe

更新命令：

sudo apt update