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Tunables

  2 minute read.

Last Modified 2021-03-17 18:59 EDT

TrueNAS allows you to add system tunables from the web interface. These can be manually defined or TrueNAS can run an autotuning script to attempt to optimize the system. Tunables are used to manage TrueNAS sysctls, loaders, and rc.conf options.

  • loader : specifies parameters to pass to the kernel or load additional modules at boot time.
  • rc.conf : enables system services and daemons and only take effect after a reboot.
  • sysctl : configures kernel parameters while the system is running and generally take effect immediately.
Adding a sysctl, loader, or rc.conf option is an advanced feature. A sysctl immediately affects the kernel running the TrueNAS system and a loader could adversely affect the ability of the TrueNAS system to successfully boot. Do not create a tunable on a production system before testing the ramifications of that change.

Configuring System Tunables

To configure a tunable, go to System > Tunables and click ADD.

SystemTunablesAdd

First, select the Type of tunable to add or modify. Enter the name of the loader, sysctl, or rc.conf variable to configure.

Next, enter the value to use for the loader, sysctl, or rc.conf. An optional description can be given.

If you wish to create the system tunable but not immediately enable it, unset the Enable checkbox. Configured tunables remain in effect until deleted or Enabled is unset.

Restarting the TrueNAS system after making sysctl changes is recommended. Some sysctls only take effect at system startup, and restarting the system guarantees that the setting values correspond with what is being used by the running system.

Be careful when adding or editing the default tunables. Changing the default tunables can make the system unusable.

Tunable

NameDescription
VariableEnter the name of the loader, sysctl, or rc.conf variable to configure. loader tunables are used to specify parameters to pass to the kernel or load additional modules at boot time. rc.conf tunables are for enabling system services and daemons and only take effect after a reboot. sysctl tunables are used to configure kernel parameters while the system is running and generally take effect immediately.
ValueEnter a value to use for the loader, sysctl, or rc.conf variable.
TypeCreating or editing a sysctl immediately updates the Variable to the configured Value. A restart is required to apply loader or rc.conf tunables. Configured tunables remain in effect until deleted or Enabled is unset.
DescriptionEnter a description of the tunable.
EnabledEnable this tunable. Unset to disable this tunable without deleting it.