firehol - an easy to use but powerful iptables stateful firewall
sudo -E firehol panic [ IP ]
firehol command [ -- conf-arg... ]
firehol CONFIGFILE [start|debug|try] [-- conf-arg... ]
firehol invokes iptables(8) to manipulate your firewall.
Run without any arguments,
firehol will present some help on usage.
When given CONFIGFILE,
firehol will use the named file instead of
/etc/firehol/firehol.conf as its configuration. If no command is given,
It is possible to pass arguments for use by the configuration file separating any conf-arg values from the rest of the arguments with
--. The arguments are accessible in the configuration using standard bash(1) syntax e.g. $1, $2, etc.
To block all communication, invoke
firehol with the
FireHOL removes all rules from the running firewall and then DROPs all traffic on all iptables(8) tables (mangle, nat, filter) and pre-defined chains (PREROUTING, INPUT, FORWARD, OUTPUT, POSTROUTING).
DROPing is not done by changing the default policy to DROP, but by adding one rule per table/chain to drop all traffic. This allows systems which do not reset all the chains to ACCEPT when starting to function correctly.
When activating panic mode, FireHOL checks for the existence of the SSH_CLIENT shell environment variable, which is set by ssh(1). If it finds this, then panic mode will allow the established SSH connection specified in this variable to operate.
In order for FireHOL to see the environment variable you must ensure that it is preserved. For sudo(8) use the
-Eand for su(1) omit the
If SSH_CLIENT is not set, the IP after the panic argument allows you to give an IP address for which all established connections between the IP address and the host in panic will be allowed to continue.
Activates the firewall using
Use of the term
restart is allowed for compatibility with common init implementations.
commit. If this word is not typed within 30 seconds, the previous firewall is restored.
/sbin/iptables -nxvL | less.
Start the firewall and then save it using iptables-save(8) to the location given by FIREHOL_AUTOSAVE. See firehol-defaults.conf(5) for more information.
The required kernel modules are saved to an executable shell script
/var/spool/firehol/last_save_modules.sh, which can be called during boot if a firewall is to be restored.
External changes may cause a firewall restored after a reboot to not work as intended where starting the firewall with FireHOL will work.
This is because as part of starting a firewall, FireHOL checks some changeable values. For instance the current kernel configuration is checked (for client port ranges), and RPC servers are queried (to allow correct functioning of the NFS service).
Enters an interactive mode where FireHOL accepts normal configuration commands and presents the generated iptables(8) commands for each of them, together with some reasoning for its purpose.
Additionally, FireHOL automatically generates a configuration script based on the successful commands given.
Some extra commands are available in
Tries to guess the FireHOL configuration needed for the current machine.
FireHOL will not stop or alter the running firewall. The configuration file is given in the standard output of firehol, thus
firehol helpme > /tmp/firehol.conf will produce the output in
The generated FireHOL configuration must be edited before use on your systems. You are required to take a number of decisions; the comments in the generated file will instruct you in the choices you must make.