Configuration variables
Configuration variables allow you to provide runtime configuration to the host OS and supervisor. These variables all begin with RESIN_. Beginning with supervisor v7.0.0, a number of them appear automatically in your dashboard when your device is provisioned.
Configuration variables can be managed at both the fleet and device level.
Note: Configuration variables defined in the dashboard will not apply to devices in local mode. You will need to define them in your balena-sync.yml.
Variable list
This list contains configuration variables that can be used with balena devices, some of which will automatically appear for devices with supervisor v7.0.0 and greater. While they may not automatically populate in the dashboard, most of these variables can still be used with older supervisor versions, so be sure to check the Valid from column:
| Name | Default | Description | Valid from |
|---|---|---|---|
| RESIN_HOST_LOG_TO_DISPLAY | Enable / Disable logs on the HDMI display | v1.7.0 | |
| RESIN_SUPERVISOR_CONNECTIVITY_CHECK | true | Enable / Disable VPN connectivity check | v1.3.0 |
| RESIN_SUPERVISOR_DELTA | false | Enable / Disable delta updates | v1.7.0 |
| RESIN_SUPERVISOR_DELTA_REQUEST_TIMEOUT | 30000 | Define the timeout when requesting a delta, in milliseconds | v3.0.0 |
| RESIN_SUPERVISOR_DELTA_RETRY_COUNT | 30 | Define the number of times a delta download should be retried | v6.2.0 |
| RESIN_SUPERVISOR_DELTA_RETRY_INTERVAL | 1000 | Define the wait time between delta download attempts, in milliseconds | v6.2.0 |
| RESIN_SUPERVISOR_LOCAL_MODE | false | Enable / Disable local mode | v4.0.0 |
| RESIN_SUPERVISOR_LOG_CONTROL | true | Enable / Disable logs being sent to the balena API | v1.3.0 |
| RESIN_SUPERVISOR_POLL_INTERVAL | 60000 | Define the balena API poll interval in milliseconds | v1.3.0 |
| RESIN_SUPERVISOR_VPN_CONTROL | true | Enable / Disable VPN | v1.3.0 |
In addition to these values, there may be some device-type specific configuration variables that can be set. For example, these values apply to Raspberry Pi devices, reflecting the contents of the config.txt file:
| Name | Default | Description |
|---|---|---|
| RESIN_HOST_CONFIG_disable_splash | 1 | Enable / Disable the balena splash screen |
| RESIN_HOST_CONFIG_dtparam | "i2c_arm=on","spi=on","audio=on" | Define DT parameters |
| RESIN_HOST_CONFIG_enable_uart | 1 | Enable / Disable UART |
| RESIN_HOST_CONFIG_gpu_mem | 16 | Define device GPU memory in megabytes |
You can find more information on updating config.txt through configuration variables in our Advanced Boot Configuration Guide.
Managing fleet configuration variables
Configuration variables defined on the fleet level control the behavior of any devices running in that fleet, unless they are redefined with a device configuration variable of the same name.
If you want to change the default value for one of the prepopulated configuration variables, make sure you are in the Fleet Configuration tab, then click activate for the variable you wish to define:
A new dialog will pop up, allowing you to define the value for your configuration variable. Click Add to apply to all devices in your fleet that do not already have an identical device configuration variable defined:
To define a custom fleet configuration variable, scroll past the automatically populated variables, then click the Add custom variable button in the lower-right corner:
As before, a dialog pops up giving you the option to define a name and value (remember, all config variable names must begin with RESIN_). Click Add to apply:
If you have already defined configuration variables at the device level, they will appear in a list below your fleet configuration variables. You can easily apply a device value to the entire fleet by clicking Define fleet-wide:
Managing device configuration variables
Device configuration variables define the behavior of a single device. If both the fleet and the device have a configuration variable of the same name, the code on the device will use the value of the device configuration variable. In other words, device configuration variables redefine (or override) fleet configuration variables.
The device configuration variable list includes the prepopulated default values. Binary (true/false) variables can be easily switched with the provided toggles. Other values can be edited by clicking the small pencil icon:
This will pop up a small dialog for editing the value:
Adding a custom device configuration variable is very similar to adding a custom fleet configuration variable: scroll past the prepopulated variables, click Add custom variable, define a name and value, and click Add.
You can override the value of a custom fleet configuration variable by clicking override in the far-right column. This will pop up the variable editing dialog, where you can change the value:
