在安装opencv时，sudo apt-get install build-essential 报错_sudo apt-get install build-essential 404

输入：sudo apt-get install build-essential
更新不完成，而且总是下载不了，网速慢
E: 无法下载 http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/dists/xenial/main/binary-i386/Packages 404 Not Found [IP: 101.6.8.193 80]

我得解决办法：更换Ubuntu源列表，我使用的Ubuntu18.04，源文件在 /etc/apt/sources.list中，首先进行备份

1. 备份sources.list

sudo cp /etc/apt/sources.list /etc/apt/sources.list_backup

2.修改 /etc/apt/sources.list 中内容
sudo gedit /etc/apt/sources.list 打开并修改源中内容

原来得源列表：

注释删除掉了，只保留原来源列表中的非注释内容，sources.list 中内容复制到本文中时，csdn就死了。。。

deb http://cn.archive.ubuntu.com/ubuntu/ bionic main restricted
deb http://cn.archive.ubuntu.com/ubuntu/ bionic-updates main restricted
deb http://cn.archive.ubuntu.com/ubuntu/ bionic universe
deb http://cn.archive.ubuntu.com/ubuntu/ bionic-updates universe
deb http://cn.archive.ubuntu.com/ubuntu/ bionic multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ bionic-updates multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu bionic-security main restricted
deb http://security.ubuntu.com/ubuntu bionic-security universe
deb http://security.ubuntu.com/ubuntu bionic-security multiverse
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/ bionic main multiverse restricted universe
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更改后得源列表

deb http://mirrors.aliyun.com/ubuntu/
bionic main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/
bionic-security main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/
bionic-updates main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/
bionic-proposed main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/
bionic-backports main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/
bionic main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/
bionic-security main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/
bionic-updates main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/
bionic-proposed main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/
bionic-backports main restricted universe multiverse
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3.更新
sudo apt-get update
sudo apt-get upgrade

参考链接

https://blog.csdn.net/weixin_44174099/article/details/89061637