ubuntu无法更新的问题，提示错误Err http://mirrors.163.com trusty Release.gpg Could not resolve 'mirrors.163.com

一般都会推荐使用国内的镜像源，比如163或者阿里云的镜像服务器
将下列文本添加到/etc/apt/sources.list文件里

cd /etc/opt/
sudo gedit source.list

阿里云

#阿里源
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

修改DNS

sudo vi /etc/resolv.conf

添加

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.1.1
#这里用的是阿里云的DNS服务器
nameserver 223.5.5.5  
nameserver 223.6.6.6

之后执行sudo apt-get update就正常了。