Ubuntu18.04 更换 国内源

1.进入root模式        sudo -s

2.进入ubuntu源的目录     cd /etc/apt

3.备份sources.list     cp sources.list sources.list.bak   

4.修改sources.list    删除sources.list中的内容，把阿里云的源复制进source.list中   

   gedit sources.list(删除原有的内容)

   复制下面阿里的源：

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

 5.更新源    apt update

6.更新软件    apt upgrade    至此，更换国内源完毕