---
title: "loki.source.journal | Grafana Agent documentation"
description: "Learn about loki.source.journal"
---

# loki.source.journal

`loki.source.journal` reads from the systemd journal and forwards them to other `loki.*` components.

Multiple `loki.source.journal` components can be specified by giving them different labels.

## Usage

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
loki.source.journal "LABEL" {
  forward_to    = RECEIVER_LIST
}
```

## Arguments

The component starts a new journal reader and fans out log entries to the list of receivers passed in `forward_to`.

`loki.source.journal` supports the following arguments:

Expand table

| Name             | Type                 | Description                                                                                            | Default | Required |
|------------------|----------------------|--------------------------------------------------------------------------------------------------------|---------|----------|
| `format_as_json` | `bool`               | Whether to forward the original journal entry as JSON.                                                 | `false` | no       |
| `max_age`        | `duration`           | The oldest relative time from process start that will be read.                                         | `"7h"`  | no       |
| `path`           | `string`             | Path to a directory to read entries from.                                                              | `""`    | no       |
| `matches`        | `string`             | Journal matches to filter. The `+` character is not supported, only logical AND matches will be added. | `""`    | no       |
| `forward_to`     | `list(LogsReceiver)` | List of receivers to send log entries to.                                                              |         | yes      |
| `relabel_rules`  | `RelabelRules`       | Relabeling rules to apply on log entries.                                                              | `{}`    | no       |
| `labels`         | `map(string)`        | The labels to apply to every log coming out of the journal.                                            | `{}`    | no       |

> **NOTE**: A `job` label is added with the full name of the component `loki.source.journal.LABEL`.

When the `format_as_json` argument is true, log messages are passed through as JSON with all of the original fields from the journal entry. Otherwise, the log message is taken from the content of the `MESSAGE` field from the journal entry.

When the `path` argument is empty, `/var/log/journal` and `/run/log/journal` will be used for discovering journal entries.

The `relabel_rules` argument can make use of the `rules` export value from a [loki.relabel](../loki.relabel/) component to apply one or more relabeling rules to log entries before they’re forwarded to the list of receivers in `forward_to`.

All messages read from the journal include internal labels following the pattern of `__journal_FIELDNAME` and will be dropped before sending to the list of receivers specified in `forward_to`. To keep these labels, use the `relabel_rules` argument and relabel them to not be prefixed with `__`.

> **NOTE**: many field names from journald start with an `_`, such as `_systemd_unit`. The final internal label name would be `__journal__systemd_unit`, with *two* underscores between `__journal` and `systemd_unit`.

## Component health

`loki.source.journal` is only reported as unhealthy if given an invalid configuration.

## Debug Metrics

- `agent_loki_source_journal_target_parsing_errors_total` (counter): Total number of parsing errors while reading journal messages.
- `agent_loki_source_journal_target_lines_total` (counter): Total number of successful journal lines read.

## Example

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
loki.relabel "journal" {
  forward_to = []

  rule {
    source_labels = ["__journal__systemd_unit"]
    target_label  = "unit"
  }
}

loki.source.journal "read"  {
  forward_to    = [loki.write.endpoint.receiver]
  relabel_rules = loki.relabel.journal.rules
  labels        = {component = "loki.source.journal"}
}

loki.write "endpoint" {
  endpoint {
    url ="loki:3100/api/v1/push"
  }
}
```

## Compatible components

`loki.source.journal` can accept arguments from the following components:

- Components that export [Loki `LogsReceiver`](../../compatibility/#loki-logsreceiver-exporters)

> Note
> 
> Connecting some components may not be sensible or components may require further configuration to make the connection work correctly. Refer to the linked documentation for more details.