W: 仓库 “https://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial Release” 没有 Release 文件。 N: 无法认证来自该源的数据，所以使

W: 仓库 “https://mirrors.tuna.tsinghua.edu.cn/ubuntu xenial Release” 没有 Release 文件。N: 无法认证来自该源的数据，所以使用它会带来潜在风险。N: 参见 apt-secure(8) 手册以了解仓库创建和用户配置方面的细节。

解决方法：更新软件源

修改/etc/apt/sources.list

sudo gedit /etc/apt/sources.list

适用于ubuntu16.04

使用aliyun，将sources.list内容修改为下面内容

# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse

适用于ubuntu18.04

使用aliyun，将sources.list内容修改为下面内容

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

适用于ubuntu20.04

使用aliyun，将sources.list内容修改为下面内容

deb http://mirrors.aliyun.com/ubuntu focal main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu focal-updates main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu focal-security main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu focal-proposed main multiverse restricted universe
deb http://mirrors.aliyun.com/ubuntu focal-backports main multiverse restricted universe

最后更新软件包

sudo apt update

or

sudo apt-get update