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).

The docker logscommand is available only for the json-file logging driver.

The 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+]

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.

The 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 syslog-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

The syslog-tag specifies a tag that identifies the container's syslog messages. By default, the system uses the first 12 characters of the container id. To override this behavior, specify a syslog-tag option

Specify 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.

Specify gelf options

The GELF logging driver supports the following options:

--log-opt gelf-address=udp://host:port
--log-opt gelf-tag="database"

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

The gelf-tag option specifies a tag for easy container identification.

Specify 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]
• fluentd-tag: specify tag for fluentd message,

When specifying a fluentd-tag value, you can use the following markup tags:

• {{.ID}}: short container id (12 characters)
• {{.FullID}}: full container id
• {{.Name}}: container name

For example, to specify both additional options:

docker run --log-driver=fluentd --log-opt fluentd-address=localhost:24224 --log-opt fluentd-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