换源

root@firefly:~# cat /etc/apt/sources.list
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

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install build-essential

查看软件包

sudo apt list --installed

查看存在版本

apt-cache madison openjdk-8-jdk

卸载软件包

sudo apt remove package_name

保留软件不升级

sudo apt-mark hold openjdk-8-jre-headless

卸载软件包(包含文件)

重启网络

/etc/init.d/networking restart

同步时间

apt-get install -y ntpd           #安装
vim /etc/ntp.conf                 #添加下面一行
server cn.pool.ntp.org
/etc/init.d/ntp restart           #重启