Settings

Besides the configuration options that every component has, OPNsense also contains a lot of general settings that you can tweak. This page contains an overview of them.

Administration

The settings on this page concerns logging into OPNsense. The “Secure Shell” settings are described under Creating Users & Groups.

Setting Explanation
Web GUI
Protocol It is strongly recommended to leave this on “HTTPS”
SSL Certificate By default, a self-signed certificate is used. Certificates can be added via System ‣ Trust ‣ Certificates.
SSL Ciphers Can be used to limit SSL cipher selection in case the system defaults are undesired. Note that restrictive use may lead to an inaccessible web GUI.
Enable HTTP Strict Transport Security Enforces loading the web GUI over HTTPS, even when the connection is hijacked (man-in-the-middle attack), and do not allow the user to trust an invalid certificate for the web GUI.
TCP port Can be useful if there are other services that are reachable via port 80/443 of the external IP, for example.
Disable web GUI redirect rule If you change the port, a redirect rule from port 80/443 will be created. Check this to disable creating this rule.
Disable logging of web GUI successful logins  
Session Timeout Time in minutes to expire idle management sessions.
Disable DNS Rebinding Checks OPNsense contains protection against DNS rebinding by filtering out DNS replies with local IPs. Check this box to disable this protection if it interferes with web GUI access or name resolution in your environment.
Alternate Hostnames Alternate, valid hostnames (to avoid false positives in referrer/DNS rebinding protection).
HTTP Compression Reduces size of transfer, at the cost of slightly higher CPU usage.
Enable access log Log all access to the Web GUI (for debuggin/analysis)
Listen interfaces Can be used to limit interfaces on which the Web GUI can be accessed. This allows freeing the interface for other services, such as HAProxy.
Disable HTTP_REFERER enforcement check The origins of requests are checked in order to provide some protection against CSRF. You can turn this off of it interferes with external scripts that interact with the Web GUI.
Console
Use the virtual terminal driver (vt) When unchecked, OPNsense will use the older sc driver.
Primary Console The primary console will show boot script output. All consoles display OS boot messages, console messages, and the console menu.
Secondary Console See above.
Serial Speed Allows adjusting the baud rate. 115200 is the most common.
Use USB-based serial ports Listen on /dev/ttyU0, /dev/ttyU1, … instead of /dev/ttyu0.
Password protect the console menu Can be unchecked to allow physical console access without password. This can avoid lock-out, but at the cost of attackers being able to do anything if they gain physical access to your system.
Authentication
Server Select one or more authentication servers to validate user credentials against. Multiple servers can make sense with remote authentication methods to provide a fallback during connectivity issues. When nothing is specified the default of “Local Database” is used.
Sudo Permit sudo usage for administrators with shell access.
Disable integrated authentication When set, console login, SSH, and other system services can only use standard UNIX account authentication.

Cron

Cron is a service that is used to execute jobs periodically. Cron jobs can be viewed by navigating to System ‣ Settings ‣ Cron. New jobs can be added by click the + button in the lower right corner.

When adding a new job or modifying an existing one, you will be presented with fields that directly reflect the cron file syntax and that mostly speak for themselves. A job needs a name, a command, command parameters (if applicable), a description (optional, but recommend) and most importantly, a schedule. All time-related fields share the same syntax:

  • An asterisk (*) can be used to mean “any”
  • Specifying multiple values is possible using the comma: 1,4,9
  • Ranges can be specified using a dash: 4-9

General

The general settings mainly concern network-related settings like the hostname. The general setting can be set by going to System ‣ Settings ‣ General. The following settings are available:

Setting Explanation
System
Hostname Hostname without domain, e.g.: firewall
Domain The domain, e.g. mycorp.com, home, office, private, etc. Do not use ‘local’ as a domain name. It will cause local hosts running mDNS (avahi, bonjour, etc.) to be unable to resolve local hosts not running mDNS.
Time zone  
Language Default language. Can be overridden by users.
Theme More themes can be installed via plug-ins.
Networking
Prefer to use IPv4 even if IPv6 is available  
DNS servers A list of DNS servers, optionally with a gateway. These DNS servers are also used for the DHCP service, DNS services and for PPTP VPN clients. When using multiple WAN connections there should be at least one unique DNS server per gateway.
Allow DNS server list to be overridden by DHCP/PPP on WAN If this option is set, DNS servers assigned by a DHCP/PPP server on the WAN will be used for their own purposes (including the DNS services). However, they will not be assigned to DHCP and PPTP VPN clients.
Do not use the local DNS service as a nameserver for this system When enabling local DNS services such as Dnsmasq and Unbound, OPNsense will use these as a nameserver. Check this option to prevent this.
Allow default gateway switching If the link where the default gateway resides fails switch the default gateway to another available one.

Tunables

Tunables are the settings that go into the sysctl.conf file, which allows tweaking of low-level system settings. They can be set by going to System ‣ Settings ‣ Tunables.

Here, the currently active settings can be viewed and new ones can be created. All valid sysctl.conf settings can be added this way if desired. A list of possible values can be obtained by issuing sysctl -a on an OPNsense shell.

Miscellaneous

As the name implies, this section contains the settings that do not fit anywhere else.

Setting Explanation
Cryptography settings  
Diffie-Hellman parameters The server and client needs to use the same parameters in order to set up a connection. How parameters are updated can be tweaked. Please leave on default unless you know why to change it.
Hardware acceleration Select your method of hardware acceleration, if present. Check the full help for hardware-specific advice.
Use /dev/crypto Old hardware crypto drivers expose the /dev/crypto interface. This is not used by newer hardware or software any more.
Thermal Sensors  
Hardware Select between No/ACPI thermal sensor driver and processor-specific drivers.
Periodic Backups  
Periodic RRD Backup Periodically backup Round Robin Database.
Periodic DHCP Leases Backup Periodically backup DHCP leases.
Periodic NetFlow Backup Periodically backup Netflow state.
Periodic Captive Portal Backup Periodically backup Captive Portal state.
Power Savings  
Use PowerD PowerD allows tweaking power conservation features. The modes are maximum (high performance), minimum (maximum power saving), adaptive (balanced), hiadaptive (balanced, but with higher performance).
On AC Power Mode  
On Battery Power Mode  
On Normal Power Mode  
Disk / Memory Settings  
Swap file Create a 2 GB swap file. This can increase performance, at the cost of increased wear on storage, especially flash.
/var RAM disk This can be useful to avoid wearing out flash storage. Everything in /var, including logs will be lost upon reboot.
/tmp RAM disk See above.
System Sounds  
Disable the startup/shutdown beep Disable beeps via the built-in speaker (“PC Speaker”)