Where is a log file with logs from a container?

You can docker inspect each container to see where their logs are:

docker inspect --format='{{.LogPath}}' $INSTANCE_ID

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And, in case you were trying to figure out where the logs were to manage their collective size, or adjust parameters of the logging itself you will find the following relevant.

Fixing the amount of space reserved for the logs

This is taken from Request for the ability to clear log history (issue 1083)):

Docker 1.8 and docker-compose 1.4 there is already exists a method to limit log size using docker compose log driver and log-opt max-size:

mycontainer:
  ...
  log_driver: "json-file"
  log_opt:
    # limit logs to 2MB (20 rotations of 100K each)
    max-size: "100k"
    max-file: "20"

In docker compose files of version '2' , the syntax changed a bit:

version: '2'
...
mycontainer:
  ...
  logging:
    #limit logs to 200MB (4rotations of 50M each)
    driver: "json-file"
    options:
      max-size: "50m"
      max-file: "4"

(note that in both syntaxes, the numbers are expressed as strings, in quotes)

Possible issue with docker-compose logs not terminating

• issue 1866: command logs doesn't exit if the container is already stopped

A container's logs can be found in :

/var/lib/docker/containers/<container id>/<container id>-json.log

(if you use the default log format which is json)