> For the complete documentation index, see [llms.txt](https://docs.cybus.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.cybus.io/2-6-1/broker/cybusmq/environment-variables.md).

# Environment Variables (CybusMQ)

Environment variables for configuring CybusMQ.

Configure CybusMQ to match your deployment requirements using environment variables.

{% hint style="info" %}
CybusMQ uses the original VerneMQ variable names.
{% endhint %}

{% hint style="warning" %}

## Prefer Helm values over environment variables in Kubernetes deployments

For Kubernetes deployments, configuration is primarily done through Helm chart values. Environment variables should only be used if there is no corresponding Helm value.
{% endhint %}

The following environment variables are available for simple configurations. If you need further options, you must provide your own configuration file in which you can use all VerneMQ configuration options.

## Environment Variables

| Environment Variable                               | Description                                                                                                                                                                                                                                             |
| -------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `DOCKER_VERNEMQ_ALLOW_REGISTER_DURING_NETSPLIT`    | Allows clients to connect even if the cluster is incomplete.                                                                                                                                                                                            |
| `DOCKER_VERNEMQ_ALLOW_PUBLISH_DURING_NETSPLIT`     | Allows clients to publish even if the cluster is incomplete.                                                                                                                                                                                            |
| `DOCKER_VERNEMQ_ALLOW_SUBSCRIBE_DURING_NETSPLIT`   | Allows clients to subscribe even if the cluster is incomplete.                                                                                                                                                                                          |
| `DOCKER_VERNEMQ_ALLOW_UNSUBSCRIBE_DURING_NETSPLIT` | Allows clients to unsubscribe even if the cluster is incomplete.                                                                                                                                                                                        |
| `MAX_OFFLINE_MESSAGES`                             | Maximum number of messages stored while a client is offline.                                                                                                                                                                                            |
| `MAX_ONLINE_MESSAGES`                              | Maximum number of messages stored while a client is online. To keep buffered messages from being dropped when a client reconnects after a network partition or other infrastructure disruption, set this close to the expected per-client MQTT traffic. |
| `PERSISTENT_CLIENT_EXPIRATION`                     | Defines how long persistent sessions are kept without client activity.                                                                                                                                                                                  |
| `DOCKER_VERNEMQ_LOG__CONSOLE__LEVEL`               | Configures the console log level.                                                                                                                                                                                                                       |


---

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