Firely Server settings with Environment Variables


It is recommended to use Environment Variables for all sensitive information you want to pass onto to Firely Server, such as connection strings and secrets.

Environment Variables for appsettings

All the settings in Firely Server settings can be overridden by environment variables on your OS. This can be useful if you want to deploy Firely Server to several machines, each having their own settings for certain options. For Using Firely Server on Docker using environment variables in the docker-compose file is currently the only way to pass settings to the container. Or if you don’t want a database password in the appsettings.json file.

The format for the environment variables is:


So you start the variable name with the prefix VONK_, and then follow the properties in the json settings, separating each level with a double underscore __. Some examples:


"Repository" : "SQL"

environment variable:


To access an embedded value, using the ‘__’ separator:


"Administration" : {
        "SqlDbOptions" : {
                "ConnectionString" : "<some connectionstring>"

environment variable:

VONK_Administration__SqlDbOptions__ConnectionString=<some connectionstring>


A colon : is also valid as a separator in some environments, but not all. For its wider support we recommend to use __. See this article for more information.

Arrays in Environment Variables

Sometimes the appsettings allow for an array of values, e.g. in the setting for AllowedProfiles in Validating incoming resources. You can address them by appending an extra __ and an index number.


"Validation": {
   "ValidateIncomingResources": "true",

environment variables:


Another example for excluding namespaces in the PipelineOptions:

"PipelineOptions": {
"Branches": [
      "Path": "/",
      "Exclude": [

environment variables:


Log settings with Environment Variables

You can control the Log settings with Environment Variables the same way as the Environment Variables for appsettings above. The difference is in the prefix. For the log settings we use ‘VONKLOG_’.


"Serilog": {
     "MinimumLevel": {
         "Override": {
             "Vonk.Configuration": "Information",

environment variable:


Note that the . in Vonk.Configuration is part of a namespace and should not be replaced by a double underscore.

Audit log settings with Environment Variables

You can control the Audit log file configuration with Environment Variables the same way as the Environment Variables for appsettings above. The difference is in the prefix. For the log settings we use ‘VONKAUDITLOG_’.


"AuditLog": {
   "WriteTo": [
         "Name": "File",
         "Args": {
            "path": "./audit/AuditLog.log"

environment variable:


Return of call stack and Environment Variables

When first implementing Firely Server or for debugging purposes it can be convenient to have the call stack returned even though the server throws a 500 error code. If no specific environment variables are set, Firely Server will return ‘Oops! Something went wrong :(’ with a 500 error code. The call stack will only appear in the log. Setting the ‘ASPNETCORE_ENVIRONMENT’ variable to production will have the same result:


When the ‘ASPNETCORE_ENVIRONMENT’ variable is set to development the call stack is returned, even when a 500 error code is thrown by the server:


Customize the location of configuration files

It is possible to change the default location of the *.instance.json configuration files by setting a reserved environment variable. See Providing settings in a different folder for details.

Changing Environment Variables on Windows

In Windows you can change the Environment Variables with Powershell or through the UI. Based on the first example above:

  • In Powershell run:
    > $env:VONK_Repository="SQL"

  • or go to your System, open the Advanced system settings –> Environment variables and create a new variable with the name VONK_Repository and set the value to SQL.