# Local file logging driver


The `local` logging driver captures output from container's stdout/stderr and
writes them to an internal storage that's optimized for performance and disk
use.

By default, the `local` driver preserves 100MB of log messages per container and
uses automatic compression to reduce the size on disk. The 100MB default value is based on a 20M default size
for each file and a default count of 5 for the number of such files (to account for log rotation).

> [!WARNING]
>
> The `local` logging driver uses file-based storage. These files are designed
> to be exclusively accessed by the Docker daemon. Interacting with these files
> with external tools may interfere with Docker's logging system and result in
> unexpected behavior, and should be avoided.

## Usage

To use the `local` driver as the default logging driver, set the `log-driver`
and `log-opt` keys to appropriate values in the `daemon.json` file. For more
about configuring Docker using `daemon.json`, see
[daemon.json](/reference/cli/dockerd/#daemon-configuration-file).



> [!NOTE]
>
> If you're using Docker Desktop, edit the daemon configuration through the
> Docker Desktop Dashboard. Open **Settings** and select **Docker Engine**.
> For details, see
> [Docker Engine settings](/desktop/settings-and-maintenance/settings/#docker-engine).


The following example sets the log driver to `local` and sets the `max-size`
option.

```json
{
  "log-driver": "local",
  "log-opts": {
    "max-size": "10m"
  }
}
```

Restart Docker for the changes to take effect for newly created containers.
Existing containers don't use the new logging configuration automatically.

You can set the logging driver for a specific container by using the
`--log-driver` flag to `docker container create` or `docker run`:

```console
$ docker run \
      --log-driver local --log-opt max-size=10m \
      alpine echo hello world
```

Note that `local` is a bash reserved keyword, so you may need to quote it in scripts.

### Options

The `local` logging driver supports the following logging options:

| Option     | Description                                                                                                                                                   | Example value              |
| :--------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------ | :------------------------- |
| `max-size` | The maximum size of the log before it's rolled. A positive integer plus a modifier representing the unit of measure (`k`, `m`, or `g`). Defaults to 20m.      | `--log-opt max-size=10m`   |
| `max-file` | The maximum number of log files that can be present. If rolling the logs creates excess files, the oldest file is removed. A positive integer. Defaults to 5. | `--log-opt max-file=3`     |
| `compress` | Toggle compression of rotated log files. Enabled by default.                                                                                                  | `--log-opt compress=false` |

### Examples

This example starts an `alpine` container which can have a maximum of 3 log
files no larger than 10 megabytes each.

```console
$ docker run -it --log-driver local --log-opt max-size=10m --log-opt max-file=3 alpine ash
```