ubuntu桌面選擇圖形介面很簡單，設定下就行，但是安裝了ubuntu server字元介面就要自己來配置了

在sources.llist中加入

deb mirror://mirrors.ubuntu.com/mirrors.txt bionic main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt bionic-backports main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt bionic-proposed main restricted universe multiverse
 

deb mirror://mirrors.ubuntu.com/mirrors.txt bionic-security main restricted universe multiverse
deb mirror://mirrors.ubuntu.com/mirrors.txt bionic-updates main restricted universe multiverse
deb-src mirror://mirrors.ubuntu.com/mirrors.txt bionic main restricted universe multiverse
deb-src mirror://mirrors.ubuntu.com/mirrors.txt bionic-backports main restricted universe multiverse
 

deb-src mirror://mirrors.ubuntu.com/mirrors.txt bionic-proposed main restricted universe multiverse
deb-src mirror://mirrors.ubuntu.com/mirrors.txt bionic-security main restricted universe multiverse
deb-src mirror://mirrors.ubuntu.com/mirrors.txt bionic-updates main restricted universe multiverse

其中bionic是版本代號，替換成當前使用的版本