firewalld — Dynamic Firewall Manager
firewalld [OPTIONS...]
firewalld provides a dynamically managed firewall with support for network/firewall zones to define the trust level of network connections or interfaces. It has support for IPv4, IPv6 firewall settings and for ethernet bridges and has a separation of runtime and permanent configuration options. It also supports an interface for services or applications to add firewall rules directly.
These are the command line options of firewalld:
-h, --helpPrints a short help text and exists.
--debug[=level]
Set the debug level for firewalld to level. The range of the debug level is 1 (lowest level) to 10 (highest level). The debug output will be written to the firewalld log file /var/log/firewalld.
--debug-gcPrint garbage collector leak information. The collector runs every 10 seconds and if there are leaks, it prints information about the leaks.
--noforkTurn off daemon forking. Force firewalld to run as a foreground process instead of as a daemon in the background.
--nopidDisable writing pid file. By default the program will write a pid file. If the program is invoked with this option it will not check for an existing server process.
firewalld has a D-Bus interface for firewall configuration of services and applications. It also has a command line client for the user. Services or applications already using D-Bus can request changes to the firewall with the D-Bus interface directly. For more information on the firewalld D-Bus interface, please have a look at firewalld.dbus(5).
firewalld provides support for zones, predefined services and ICMP types and has a separation of runtime and permanent configuration options. Permanent configuration is loaded from XML files in /usr/lib/firewalld or /etc/firewalld (see the section called “Directories”).
If NetworkManager is not used, there are some limitations: firewalld will not get notified about network device renames.
If firewalld gets started after the network is already up, the connections and manually created interfaces are not bound to a zone.
You can add them to a zone with firewall-cmd [--permanent] --zone=zone --add-interface=interface,
but make sure that if there's a /etc/sysconfig/network-scripts/ifcfg-interface,
the zone specified there with ZONE=zone
is the same (or both are empty/missing for default zone), otherwise the behaviour would be undefined.
A network or firewall zone defines the trust level of the interface used for a connection. There are several pre-defined zones provided by firewalld. Zone configuration options and generic information about zones are described in firewalld.zone(5)
A service can be a list of local ports and destinations and additionally also a list of firewall helper modules automatically loaded if a service is enabled. Service configuration options and generic information about services are described in firewalld.service(5). The use of predefined services makes it easier for the user to enable and disable access to a service.
The Internet Control Message Protocol (ICMP) is used to exchange information and also error messages in the Internet Protocol (IP). ICMP types can be used in firewalld to limit the exchange of these messages. For more information, please have a look at firewalld.icmptype(5).
Runtime configuration is the actual active configuration and is not permanent. After reload/restart of the service or a system reboot, runtime settings will be gone if they haven't been also in permanent configuration.
firewalld supports two configuration directories:
/usr/lib/firewalld
This directory contains the default and fallback configuration provided by firewalld for icmptypes, services and zones. The files provided with the firewalld package should not get changed and the changes are gone with an update of the firewalld package. Additional icmptypes, services and zones can be provided with packages or by creating files.
/etc/firewalldThe system or user configuration stored here is either created by the system administrator or by customization with the configuration interface of firewalld or by hand. The files will overload the default configuration files.
To manually change settings of pre-defined icmptypes, zones or services, copy the file from the default configuration directory to the corresponding directory in the system configuration directory and change it accordingly.
For more information on icmptypes, please have a look at the firewalld.icmptype(5) man page, for services at firewalld.service(5) and for zones at firewalld.zone(5).