home-assistant.io/source/_components/system_log.markdown

---
layout: page
title: "System Log"
description: "Summary of errors and warnings in Home Assistant during runtime."
date: 2017-11-11 18:00
sidebar: true
comments: false
sharing: true
footer: true
logo: home-assistant.png
ha_category: Other
ha_release: 0.58
ha_qa_scale: internal
---

The `system_log` component stores information about all logged errors and warnings in Home Assistant. All collected information is accessible directly in the frontend, just navigate to the `Info` section under `Developer Tools`. In order to not overload Home Assistant with log data, only the 50 last errors and warnings will be stored. Older entries are automatically discarded from the log. It is possible to change the number of stored log entries using the parameter `max_entries`.

## {% linkable_title Configuration %}

This component is automatically loaded by the `frontend` (so no need to do anything if you are using the frontend). If you are not doing so, or if you wish to change a parameter, add the following section to your `configuration.yaml` file:

```yaml
system_log:
  max_entries: MAX_ENTRIES
```

{% configuration %}
max_entries:
  description: Number of entries to store (older entries are discarded).
  required: false
  type: integer
  default: 50
fire_event:
  description: Whether events are fired (required when used for triggers).
  required: false
  type: string
  default: false
{% endconfiguration %}

## {% linkable_title Services %}

### {% linkable_title Service `clear` %}

To manually clear the system log, call this service.

### {% linkable_title Service `write` %}

Write a log entry

| Service data attribute | Optional | Description                                                                     |
| ---------------------- | -------- | ------------------------------------------------------------------------------- |
| `message`              | no       | Message to log                                                                  |
| `level`                | yes      | Log level: debug, info, warning, error, critical. Defaults to 'error'.          |
| `logger`               | yes      | Logger name under which to log the message. Defaults to 'system_log.external'.  |

## {% linkable_title Events %}

Errors and warnings are posted as the event `system_log_event`, so it is possible to write automations that trigger whenever a warning or error occurs. The following information is included in each event:

| Field       | Description                                                                 |
|-------------------------------------------------------------------------------------------|
| `level`     | Either `WARNING` or `ERROR` depending on severity.                          |
| `source`    | File that triggered the error, e.g., `core.py` or `media_player/yamaha.py`. |
| `exception` | Full stack trace if available, an empty string otherwise.                   |
| `message`   | Descriptive message of the error, e.g., "Error handling request".           |
| `timestamp` | Unix timestamp with as a double, e.g., 1517241010.237416.                   |

Live examples of these events can be found in the Home Assistant log file (`home-assistant.log`) or by just looking in the system log. An example could, for instance, look like this:

```text
2019-02-14 16:20:35 ERROR (MainThread) [homeassistant.loader] Unable to find component system_healt
2019-02-14 16:20:36 ERROR (MainThread) [homeassistant.components.device_tracker] Error setting up platform google_maps
Traceback (most recent call last):
  File "/home/fab/Documents/repos/ha/home-assistant/homeassistant/components/device_tracker/__init__.py", line 184, in
[...]
```

The message ("Unable to find component system_healt"), source (`homeassistant.loader`) and level (`ERROR`) can easily be extracted from the log. The exact timestamp and if there is a stack trace that's shown as well. Here is another error caused by the `google_map` integration with additional output present.

## {% linkable_title Examples  %}

Here are some examples using the events posted by `system_log`. `fire_event` must be set to `true` for these to work.

### {% linkable_title Counting Number of Warnings %}

This will create a `counter` that increases every time a warning is logged:

```yaml
counter:
  warning_counter:
    name: Warnings
    icon: mdi:alert

automation:
  - alias: Count warnings
    trigger:
      platform: event
      event_type: system_log_event
      event_data:
        level: WARNING
    action:
      service: counter.increment
      entity_id: counter.warning_counter
```

### {% linkable_title Conditional Messages %}

This automation will create a persistent notification whenever an error or warning is logged that has the word "service" in the message:

{% raw %}
```yaml
automation:
  - alias: Create notifications for "service" errors
    trigger:
      platform: event
      event_type: system_log_event
    condition:
      condition: template
      value_template: '{{ "service" in trigger.event.data.message }}'
    action:
      service: persistent_notification.create
      data_template:
        title: Something bad happened
        message: '{{ trigger.event.data.message }}'
```
{% endraw %}

### {% linkable_title Writing to log %}

This automation will create a new log entry when the door is opened:

{% raw %}
```yaml
automation:
  - alias: Log door opened
    trigger:
      platform: state
      entity_id: binary_sensor.door
      from: 'off'
      to: 'on'
    action:
      service: system_log.write
      message: 'Door opened!'
      level: info
```
{% endraw %}