一、故障现象
1、启动防火墙
# systemctl start firewalld
Failed to start firewalld.service: Unit is masked.
（启动防火墙失败：防火墙被锁定）
二、解决方法
1、防火墙解锁
# systemctl unmask firewalld
输出如下结果：
Removed symlink /etc/systemd/system/firewalld.service.
（移除符号链接）
2、再次启动firewalld：
# systemctl start firewalld
3、查看firewalld状态：
# systemctl status firewalld
输出如下结果：
● firewalld.service – firewalld – dynamic firewall daemon
Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
Active: active (running) since 四 2019-06-06 14:59:42 CST; 6s ago
Docs: man:firewalld(1)
Main PID: 31046 (firewalld)
Tasks: 2
Memory: 25.9M
CGroup: /system.slice/firewalld.service
└─31046 /usr/bin/python -Es /usr/sbin/firewalld –nofork –nopid
6月 06 14:59:41 node-3 systemd[1]: Starting firewalld – dynamic firewall daemon…
6月 06 14:59:42 node-3 systemd[1]: Started firewalld – dynamic firewall daemon.
4Active: active (running) 表示防火墙已经启动。
