ubuntu安装nginx

先stop apache2，否则会报错。
'''
stop apache2

sudo systemctl stop apache2.service

prevent apache2 to start at boot

sudo systemctl disable apache2.service

Reinstall nginx

sudo apt-get install nginx
'''

然后参考以下文档：https://www.digitalocean.com/community/tutorials/how-to-install-nginx-on-ubuntu-18-04-quickstart