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aliases = ["/engine/reference/logging/overview/"]
title = "Configuring Logging Drivers"
description = "Configure logging driver."
keywords = ["docker, logging, driver, Fluentd"]
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parent = "smn_logging"
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# Configure logging drivers

The container can have a different logging driver than the Docker daemon. Use
the `--log-driver=VALUE` with the `docker run` command to configure the
container's logging driver. The following options are supported:

| `none`      | Disables any logging for the container. `docker logs` won't be available with this driver.                                    |
|-------------|-------------------------------------------------------------------------------------------------------------------------------|
| `json-file` | Default logging driver for Docker. Writes JSON messages to file.                                                              |
| `syslog`    | Syslog logging driver for Docker. Writes log messages to syslog.                                                              |
| `journald`  | Journald logging driver for Docker. Writes log messages to `journald`.                                                        |
| `gelf`      | Graylog Extended Log Format (GELF) logging driver for Docker. Writes log messages to a GELF endpoint likeGraylog or Logstash. |
| `fluentd`   | Fluentd logging driver for Docker. Writes log messages to `fluentd` (forward input).                                          |
| `awslogs`   | Amazon CloudWatch Logs logging driver for Docker. Writes log messages to Amazon CloudWatch Logs.                              |
| `splunk`    | Splunk logging driver for Docker. Writes log messages to `splunk` using HTTP Event Collector.                                 |
| `etwlogs`   | ETW logging driver for Docker on Windows. Writes log messages as ETW events.                                                  |

The `docker logs`command is available only for the `json-file` and `journald`
logging drivers.

The `labels` and `env` options add additional attributes for use with logging drivers that accept them. Each option takes a comma-separated list of keys. If there is collision between `label` and `env` keys, the value of the `env` takes precedence.

To use attributes, specify them when you start the Docker daemon.

```
docker daemon --log-driver=json-file --log-opt labels=foo --log-opt env=foo,fizz
```

Then, run a container and specify values for the `labels` or `env`.  For example, you might use this:

```
docker run --label foo=bar -e fizz=buzz -d -P training/webapp python app.py
```

This adds additional fields to the log depending on the driver, e.g. for
`json-file` that looks like:

    "attrs":{"fizz":"buzz","foo":"bar"}


## json-file options

The following logging options are supported for the `json-file` logging driver:

    --log-opt max-size=[0-9+][k|m|g]
    --log-opt max-file=[0-9+]
    --log-opt labels=label1,label2
    --log-opt env=env1,env2

Logs that reach `max-size` are rolled over. You can set the size in kilobytes(k), megabytes(m), or gigabytes(g). eg `--log-opt max-size=50m`. If `max-size` is not set, then logs are not rolled over.

`max-file` specifies the maximum number of files that a log is rolled over before being discarded. eg `--log-opt max-file=100`. If `max-size` is not set, then `max-file` is not honored.

If `max-size` and `max-file` are set, `docker logs` only returns the log lines from the newest log file.


## syslog options

The following logging options are supported for the `syslog` logging driver:

    --log-opt syslog-address=[tcp|udp|tcp+tls]://host:port
    --log-opt syslog-address=unix://path
    --log-opt syslog-facility=daemon
    --log-opt syslog-tls-ca-cert=/etc/ca-certificates/custom/ca.pem
    --log-opt syslog-tls-cert=/etc/ca-certificates/custom/cert.pem
    --log-opt syslog-tls-key=/etc/ca-certificates/custom/key.pem
    --log-opt syslog-tls-skip-verify=true
    --log-opt tag="mailer"

`syslog-address` specifies the remote syslog server address where the driver connects to.
If not specified it defaults to the local unix socket of the running system.
If transport is either `tcp` or `udp` and `port` is not specified it defaults to `514`
The following example shows how to have the `syslog` driver connect to a `syslog`
remote server at `192.168.0.42` on port `123`

    $ docker run --log-driver=syslog --log-opt syslog-address=tcp://192.168.0.42:123

The `syslog-facility` option configures the syslog facility. By default, the system uses the
`daemon` value. To override this behavior, you can provide an integer of 0 to 23 or any of
the following named facilities:

* `kern`
* `user`
* `mail`
* `daemon`
* `auth`
* `syslog`
* `lpr`
* `news`
* `uucp`
* `cron`
* `authpriv`
* `ftp`
* `local0`
* `local1`
* `local2`
* `local3`
* `local4`
* `local5`
* `local6`
* `local7`

`syslog-tls-ca-cert` specifies the absolute path to the trust certificates
signed by the CA. This option is ignored if the address protocol is not `tcp+tls`.

`syslog-tls-cert` specifies the absolute path to the TLS certificate file.
This option is ignored if the address protocol is not `tcp+tls`.

`syslog-tls-key` specifies the absolute path to the TLS key file.
This option is ignored if the address protocol is not `tcp+tls`.

`syslog-tls-skip-verify` configures the TLS verification.
This verification is enabled by default, but it can be overriden by setting
this option to `true`. This option is ignored if the address protocol is not `tcp+tls`.

By default, Docker uses the first 12 characters of the container ID to tag log messages.
Refer to the [log tag option documentation](log_tags.md) for customizing
the log tag format.


## journald options

The `journald` logging driver stores the container id in the journal's `CONTAINER_ID` field. For detailed information on
working with this logging driver, see [the journald logging driver](journald.md)
reference documentation.

## gelf options

The GELF logging driver supports the following options:

    --log-opt gelf-address=udp://host:port
    --log-opt tag="database"
    --log-opt labels=label1,label2
    --log-opt env=env1,env2

The `gelf-address` option specifies the remote GELF server address that the
driver connects to. Currently, only `udp` is supported as the transport and you must
specify a `port` value. The following example shows how to connect the `gelf`
driver to a GELF remote server at `192.168.0.42` on port `12201`

    $ docker run --log-driver=gelf --log-opt gelf-address=udp://192.168.0.42:12201

By default, Docker uses the first 12 characters of the container ID to tag log messages.
Refer to the [log tag option documentation](log_tags.md) for customizing
the log tag format.

The `labels` and `env` options are supported by the gelf logging
driver. It adds additional key on the `extra` fields, prefixed by an
underscore (`_`).

    // […]
    "_foo": "bar",
    "_fizz": "buzz",
    // […]


## fluentd options

You can use the `--log-opt NAME=VALUE` flag to specify these additional Fluentd logging driver options.

 - `fluentd-address`: specify `host:port` to connect [localhost:24224]
 - `tag`: specify tag for `fluentd` message,
 - `fail-on-startup-error`: true/false; Should the logging driver fail container startup in case of connect error during startup. Default: true (backwards compatible)
 - `buffer-limit`: Size limit (bytes) for the buffer which is used to buffer messages in case of connection outages. Default: 1M

For example, to specify both additional options:

`docker run --log-driver=fluentd --log-opt fluentd-address=localhost:24224 --log-opt tag=docker.{{.Name}}`

If container cannot connect to the Fluentd daemon on the specified address,
the container stops immediately. For detailed information on working with this
logging driver, see [the fluentd logging driver](fluentd.md)


## Specify Amazon CloudWatch Logs options

The Amazon CloudWatch Logs logging driver supports the following options:

    --log-opt awslogs-region=<aws_region>
    --log-opt awslogs-group=<log_group_name>
    --log-opt awslogs-stream=<log_stream_name>


For detailed information on working with this logging driver, see [the awslogs logging driver](awslogs.md) reference documentation.

## Splunk options

The Splunk logging driver requires the following options:

    --log-opt splunk-token=<splunk_http_event_collector_token>
    --log-opt splunk-url=https://your_splunk_instance:8088

For detailed information about working with this logging driver, see the [Splunk logging driver](splunk.md)
reference documentation.

## ETW logging driver options

The etwlogs logging driver does not require any options to be specified. This logging driver will forward each log message
as an ETW event. An ETW listener can then be created to listen for these events. 

For detailed information on working with this logging driver, see [the ETW logging driver](etwlogs.md) reference documentation.