moby--moby/docs/reference/logging/overview.md

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.

The docker logscommand 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]://host:port
--log-opt syslog-address=unix://path
--log-opt syslog-facility=daemon
--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

By default, Docker uses the first 12 characters of the container ID to tag log messages. Refer to the log tag option documentation 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 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 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,

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

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 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 reference documentation.