Customize log driver output
Estimated reading time: 1 minuteThe tag log option specifies how to format a tag that identifies the
container’s log messages. By default, the system uses the first 12 characters of
the container ID. To override this behavior, specify a tag option:
$ docker run --log-driver=fluentd --log-opt fluentd-address=myhost.local:24224 --log-opt tag="mailer"
Docker supports some special template markup you can use when specifying a tag’s value:
| Markup | Description |
|---|---|
{{.ID}} |
The first 12 characters of the container ID. |
{{.FullID}} |
The full container ID. |
{{.Name}} |
The container name. |
{{.ImageID}} |
The first 12 characters of the container’s image ID. |
{{.ImageFullID}} |
The container’s full image ID. |
{{.ImageName}} |
The name of the image used by the container. |
{{.DaemonName}} |
The name of the docker program (docker). |
For example, specifying a --log-opt tag="{{.ImageName}}/{{.Name}}/{{.ID}}" value yields syslog log lines like:
Aug 7 18:33:19 HOSTNAME hello-world/foobar/5790672ab6a0[9103]: Hello from Docker.
At startup time, the system sets the container_name field and {{.Name}} in
the tags. If you use docker rename to rename a container, the new name is not
reflected in the log messages. Instead, these messages continue to use the
original container name.