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.

Listen interfaces

Warning

Before considering the use of manual selected interfaces, make sure to read this chapter so you are aware of the pitfalls upfront. Misconfigurations likely lead to a non accesible web interface and/or missing ssh access.

Both the WebUI and the Secure Shell server support the option to only listen on specific interfaces, the use of this option however comes with clear warnings which you do need to be aware of before deciding to use this option.

By default (our recommended settings), these services listen on all addresses (interfaces).

If for whatever reason, you do need to listen only on specific interfaces, the following rules apply:

• The interface must always be available, so do not try to bind to vpn instances of any kind (OpenVPN, Wireguard, …)

• The addressing must be fully static, so no IPv6 tracking configured for example

As the webgui is not able to predict with 100% certainty that these rules do apply, it is possible to select interfaces that don’t support binding for these services.

Note

When facing issues with the webgui (and/or ssh) and the above rules are not met, please do not bother to open a ticket as these are unsupported scenario’s.

Tip

In case (for any service) one would like to prevent binding on all interfaces, it is possible to add a loopback interface (Interfaces->Other Types->Loopback), assign an ip address and bind to that.

If traffic is being routed through the firewall, the “loopback ip” (some private addres, not in the loopback range) should be directly accessible from the network behind it. For example use an address like 192.192.192.192/32 to access the web interface while your own network is using 192.168.1.0/24.

Technologies like Network Address Translation can also be combined if the other end is not aware of the route to this single address.

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.
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.
Session Timeout	Time in minutes to expire idle management sessions.
DNS Rebind Check	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.
Access log	Log all access to the Web GUI for debugging/analysis.
Server Log	Display all web GUI errors in the main system log.
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.
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.

Secure Shell

User accounts can be used for logging in to the web frontend, as well as for logging in to the console (via VGA, serial or SSH). The latter will only work if the user shell is not set to /sbin/nologin.

In order to access OPNsense via SSH, SSH access will need to be configured via System ‣ Settings ‣ Administration. Under the “Secure Shell” heading, the following options are available:

Secure Shell Server	Enable a secure shell service
Login Group	Select the allowed groups for remote login. The “wheel” group is always set for recovery purposes and an additional local group can be selected at will. Do not yield remote access to non-administrators as every user can access system files using SSH or SFTP.
Permit Root Login	Root login is generally discouraged. It is advised to log in via another user and switch to root afterwards.
Permit password login	When disabled, authorized keys need to be configured for each User that has been granted secure shell access.
SSH port	Port to listen on, default is 22
Listen Interfaces	Only accept connections from the selected interfaces. Leave empty to listen globally. Use with extreme care.
Key exchange algorithms	The key exchange methods that are used to generate per-connection keys
Ciphers	The ciphers to encrypt the connection
MACs	The message authentication codes used to detect traffic modification
Host key algorithms	Specifies the host key algorithms that the server offers
Public key signature algorithms	The signature algorithms that are used for public key authentication

Console

In case of an emergency, it’s always practical to make sure to configure a console to be able to access the firewall when network connectivity is not possible.

Tip

After initial installation, always make sure to test if the console actually works. When concluding the console is not functional when you need it can be very unpractical.

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

The authentication section of the Administrationm settings offers general security settings for users logging into the firewall.

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. |
Disable integrated authentication	When set, console login, SSH, and other system services can only use | standard UNIX account authentication. |
Sudo	Permit sudo usage for administrators with shell access. |
User OTP seed	Select groups which are allowed to generate their own OTP seed on the | password page. |

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

Available cron jobs are registered in the backend to prevent command injection and privilege escalation. These can be found under Command and may allow an additional Parameter. Restart and reload actions are self-explanatory. They take no parameters and will restart (usually slower stop and start of a process) or reload (usually a faster SIGHUP) the respective service. The availability of restart and reload is subject to their respective services as not all software will support a reload for implementational reasons.

The most common core commands are as follows:

Command in GUI	Command in shell	Supported parameters	Background information
Update and reload firewall aliases	configctl filter refresh_aliases	No parameters	Updates IP aliases for DNS entries and MAC addresses as well as URL tables.
Firmware update check	configctl firmware poll	No parameters	Refresh current update status from firmware mirror for e.g. remote status check via API. Note this utilizes a skew interval of 25 minutes.
Firmware changelog update	configctl firmware changelog cron	No parameters	Refresh current changelog status from authoritative firmware location to preview changelogs for new versions. Note this utilizes a skew interval of 25 minutes and is also performed by the firmware update check.
Automatic firmware update	configctl firmware auto-update	No parameters	Perform a minor update if applicable.
Update and reload intrusion detection rules	configctl ids update	No parameters	Fetches remote rules and reloads the IDS instance to make use of newly fetched rules.
Periodic interface reset	configctl interface reconfigure [identifier]	identifier: Internal name of the interface as shown in assignments or overview page, e.g. “lan”, “wan”, “optX”.	Cycle through an interface reset that removes all connectivity and reactivates it cleanly.
Download and reload external proxy ACLs	configctl proxy fetchacls	No parameters	Fetch and activate the external ACL files for configured blocklists.
Remote backup	configctl system remote backup	No parameters	Trigger the remote backup at the specified time as opposed to its nightly default.
Issue a reboot	configctl system reboot	No parameters	Perform a reboot at the specified time.
HA update and reconfigure backup	configctl system ha_reconfigure_backup	No parameters	Synchronize the configuration to the backup firewall and restart its services to apply the changes.
Update Unbound DNSBLs	configctl unbound dnsbl	No parameters	Update the the DNS blocklists and apply the changes to Unbound.
ZFS pool trim	configctl zfs trim [pool]	pool: ZFS pool name to perform the action on	Initiates an immediate on-demand TRIM operation for all of the free space in a pool. This operation informs the underlying storage devices of all blocks in the pool which are no longer allocated and allows thinly provisioned devices to reclaim the space.
ZFS pool scrub	configctl zfs scrub [pool]	pool: ZFS pool name to perform the action on	Begins a scrub or resumes a paused scrub. The scrub examines all data in the specified pools to verify that it checksums correctly. For replicated (mirror, raidz, or draid) devices, ZFS automatically repairs any damage discovered during the scrub.

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 loader.conf and sysctl.conf files, 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. A list of possible values can be obtained by issuing sysctl -a on an OPNsense shell. Additional tunables may exist depending on boot loader capabilities and kernel module support.

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”)

Logging

Local log settings can be found at System ‣ Settings ‣ Logging, tab “Local”.

The regular log files will use the following standard pattern on disk /var/log/<application>/<application>_[YYYYMMDD].log (one file per day). Our user interface provides an integrated view stitching all collected files together. Available settings may change the appearance on disk depending on space and time constraints for log rotation.

Many plugins have their own logs. In the UI, they are grouped with the settings of that plugin. They mostly log to /var/log/ in text format, so you can view or follow them with tail.

An overview of the local settings:

Setting	Explanation
Enable local logging	Disable to avoid wearing out flash memory when applicable and set up remote logging instead.
Maximum preserved files	Configures the number of days to keep logs or the number of files if “maximum file size” option is used.
Maximum file size	Limit the file size of the logs instead of keeping one log per day.

Remote log settings can be found at System ‣ Settings ‣ Logging, tab “Remote”.

Add a new Destination to set up a remote target destination.

Setting	Explanation
Enabled	Master on/off switch.
Transport	Protocol to use for syslog.
Applications	Select a list of applications to send to remote syslog. Leave empty for all.
Levels	Choose which levels to include, omit to select all.
Facilities	Choose which facilities to include, omit to select all.
Hostname	Hostname or IP address where to send logs to.
Port	Port to use, usually 514.
Certificate	Client certificate to use (when selecting a tls transport type)
Description	Set a description for you own use.

Note

When using syslog over TLS, make sure both ends are configured properly (certificates and hostnames), certificate errors are quite common in these type of setups. On OPNsense the general system log usually contains more details. When it comes to tracking syslog-ng messages, this is usually a good resource.

A reconfigure doesn’t always apply the new tls settings instantly, if that’s not the case best stop and start syslog in OPNsense (using the gui).

To activate any changed settings use the “Apply” button below.

To clear all the logs on the system use the “Reset Log Files” button.