正常情况
1.ubuntu正常使用终端进入图形化界面；通过安装图形化界面即可；
2.确认系统能够上网：sudo dhclient eth0
eth0是物理网卡；即光纤以太网接口卡，系统默认网卡。
3.更新仓库和包列表：sudo apt-get update && sudo apt-get upgrade
4.安装桌面：sudo apt-get install ubuntu-desktop
非正常情况
由于运行某些脚本修改系统参数，导致原有的图形化界崩溃。需要恢复之图形化界面。
1.确认系统能够上网：sudo dhclient eth0
2.输出：cannot find device "eth0"：网卡已经被重命名
3.查看重命名的网卡：dmesg | grep eth
4.xxxx：renamed from eth0
5.重新联网：sudo dhclient xxxx
6.测网：ping www.baidu.com
7.更新软件源：sudo apt-get update
8.更换国内源：
`deb mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb-src mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse deb-src mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse deb-src mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse deb-src mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse deb-src mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse `
