Ubuntu 18.04.4 LTS 更换国内系统源

Ubuntu 18.04.4 LTS 更换国内系统源

  1.1) 好习惯先做备份在干活：
      mv /etc/apt/sources.list /etc/apt/sources.list.bak

  1.2) 查看ubuntu版本:
      lsb_release -c | grep -o "\s.*"
	      bionic

  1.3) 阿里云的源(将下列内容复制/etc/apt/sources.list)
      vim /etc/apt/sources.list

      *** 注意将$SYS_VERSION替换为上一步中获取的版本信息。***这点非常重要，否则会失败。(我这里的版本是：bionic) ***

## 阿里云的源(将下列内容复制/etc/apt/sources.list)：
deb http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION-backports main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ $SYS_VERSION-proposed main restricted universe multiverse

   1.4) 执行更新命令：
        apt-get update