> `log-opts` configuration options in the `daemon.json` configuration file must
> be provided as strings. Boolean and numeric values (such as the value for
> `max-file` in the example above) must therefore be enclosed in quotes (`"`).

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 json-file --log-opt max-size=10m \
      alpine echo hello world
```

### Options

The `json-file` logging driver supports the following logging options:

| Option         | Description                                                                                                                                                                                                   | Example value                                      |
| :------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | :------------------------------------------------- |
| `max-size`     | The maximum size of the log before it is rolled. A positive integer plus a modifier representing the unit of measure (`k`, `m`, or `g`). Defaults to -1 (unlimited).                                          | `--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. **Only effective when `max-size` is also set.** A positive integer. Defaults to 1. | `--log-opt max-file=3`                             |
| `labels`       | Applies when starting the Docker daemon. A comma-separated list of logging-related labels this daemon accepts. Used for advanced [log tag options](log_tags.md).                                              | `--log-opt labels=production_status,geo`           |
| `labels-regex` | Similar to and compatible with `labels`. A regular expression to match logging-related labels. Used for advanced [log tag options](log_tags.md).                                                              | `--log-opt labels-regex=^(production_status\|geo)` |
| `env`          | Applies when starting the Docker daemon. A comma-separated list of logging-related environment variables this daemon accepts. Used for advanced [log tag options](log_tags.md).                               | `--log-opt env=os,customer`                        |
| `env-regex`    | Similar to and compatible with `env`. A regular expression to match logging-related environment variables. Used for advanced [log tag options](log_tags.md).                                                  | `--log-opt env-regex=^(os\|customer)`              |
| `compress`     | Toggles compression for rotated logs. Default is `disabled`.                                                                                                                                                  | `--log-opt compress=true`                          |

### 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-opt max-size=10m --log-opt max-file=3 alpine ash
```