Clearsigned file isn’t valid, got ‘NOSPLIT’ (does the network require authentication?)

ubuntu 更新apt 软件源 失败

// 加入以下软件源地址后执行 apt-get update 后提示错误Clearsigned file isn’t valid, got ‘NOSPLIT’ (does the network require authentication

# 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.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/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.tuna.tsinghua.edu.cn/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.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted universe multiverse

出现这个错误主要愿意是因为网路不通导致的，很多同学和我一样用公司或者学校的内网上网，然后用虚拟机做一些开发，所以这里虚拟机可以上网但是却浏览器也能打开网页但是软件源更新失败，主要是因为DNS 域名解析错误

只需要在设置dns 解析服务器114.114.114.114重启网络连接即可

来源：xubaipei柏培