问题：
## ubuntu 18.04
apt install nodejs
E: 无法获得锁 /var/lib/dpkg/lock-frontend - open (11: 资源暂时不可用)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?
原因：apt update后提示有多个软件包可以升级。软件包未升级结束。
解决：多执行几次apt update再apt install
问题：nginx重启异常
/usr/local/nginx/sbin/nginx -c /usr/local/nginx/conf/nginx.conf
/usr/local/nginx/sbin/nginx -s reload
