[firewalld] Failed to start firewalld.service: Unit is masked.

[root@centos7 ~]# systemctl start firewalld
Failed to start firewalld.service: Unit is masked.

Failed to start firewalld.service: Unit is masked.

출력시 systemctl unmask firewalld

[root@centos7 ~]# systemctl unmask firewalld
Removed symlink /etc/systemd/system/firewalld.service.

[root@centos7 html]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
   Active: failed (Result: timeout) since Fri 2021-02-19 00:10:24 UTC; 4h 15min ago
     Docs: man:firewalld(1)
  Process: 8019 ExecStart=/usr/sbin/firewalld --nofork --nopid $FIREWALLD_ARGS (code=exited, status=0/SUCCESS)
 Main PID: 8019 (code=exited, status=0/SUCCESS)

Feb 19 00:08:54 centos7.localdomain systemd[1]: Starting firewalld - dynamic firewall daemon...
Feb 19 00:08:54 centos7.localdomain firewalld[8019]: WARNING: AllowZoneDrifting is enabled. This is con...ow.
Feb 19 00:10:24 centos7.localdomain systemd[1]: firewalld.service start operation timed out. Terminating.
Feb 19 00:10:24 centos7.localdomain systemd[1]: Failed to start firewalld - dynamic firewall daemon.
Feb 19 00:10:24 centos7.localdomain systemd[1]: Unit firewalld.service entered failed state.
Feb 19 00:10:24 centos7.localdomain systemd[1]: firewalld.service failed.
Hint: Some lines were ellipsized, use -l to show in full.

unmask firewalld 후에도 failed 경우에는

systemctl stop firewalld

pkill -f firewalld

systemctl start firewalld

[root@centos7 html]# systemctl stop firewalld.service
[root@centos7 html]#
[root@centos7 html]# pkill -f firewalld
[root@centos7 html]#
[root@centos7 html]# systemctl start firewalld
[root@centos7 html]#
[root@centos7 html]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
   Active: active (running) since Fri 2021-02-19 04:35:45 UTC; 6s ago
     Docs: man:firewalld(1)
 Main PID: 14319 (firewalld)
   CGroup: /system.slice/firewalld.service
           └─14319 /usr/bin/python2 -Es /usr/sbin/firewalld --nofork --nopid

Feb 19 04:35:45 centos7.localdomain systemd[1]: Starting firewalld - dynamic firewall daemon...
Feb 19 04:35:45 centos7.localdomain systemd[1]: Started firewalld - dynamic firewall daemon.
Feb 19 04:35:46 centos7.localdomain firewalld[14319]: WARNING: AllowZoneDrifting is enabled. This is co...ow.
Hint: Some lines were ellipsized, use -l to show in full.