linux下firewalld被Failed to start firewalld.service: Unit is masked的解决

//系统
CentOS Linux release 7.7.1908 (AltArch)

//现象
# systemctl start firewalld.service
Failed to start firewalld.service: Unit is masked.
//可以看到firewall被锁定了，无法正常使用
//解决(解除锁定)
# systemctl unmask firewalld
Removed symlink /etc/systemd/system/firewalld.service.

//重新锁定
# systemctl mask firewalld
Created symlink from /etc/systemd/system/firewalld.service to /dev/null.