ubuntu系统启动时等待网络服务问题

ubuntu在启动时会启动systemd service，常常会卡在网络服务上。下面是一些可以省去网络等待的方法。参考https://askubuntu.com/questions/972215/a-start-job-is-running-for-wait-for-network-to-be-configured-ubuntu-server-17-1

systemctl disable systemd-networkd-wait-online.service
systemctl mask systemd-networkd-wait-online.service