github.com/iamlotus/docker@v1.8.1/docs/reference/logging/journald.md (about)

     1  <!--[metadata]>
     2  +++
     3  title = "journald logging driver"
     4  description = "Describes how to use the fluentd logging driver."
     5  keywords = ["Fluentd, docker, logging, driver"]
     6  [menu.main]
     7  parent = "smn_logging"
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     9  <![end-metadata]-->
    10  
    11  # Journald logging driver
    12  
    13  The `journald` logging driver sends container logs to the [systemd
    14  journal](http://www.freedesktop.org/software/systemd/man/systemd-journald.service.html).  Log entries can be retrieved using the `journalctl`
    15  command or through use of the journal API.
    16  
    17  In addition to the text of the log message itself, the `journald` log
    18  driver stores the following metadata in the journal with each message:
    19  
    20  | Field               | Description |
    21  ----------------------|-------------|
    22  | `CONTAINER_ID`      | The container ID truncated to 12 characters. |
    23  | `CONTAINER_ID_FULL` | The full 64-character container ID. |
    24  | `CONTAINER_NAME`    | The container name at the time it was started. If you use `docker rename` to rename a container, the new name is not reflected in the journal entries. |
    25  
    26  ## Usage
    27  
    28  You can configure the default logging driver by passing the
    29  `--log-driver` option to the Docker daemon:
    30  
    31      docker --log-driver=journald
    32  
    33  You can set the logging driver for a specific container by using the
    34  `--log-driver` option to `docker run`:
    35  
    36      docker run --log-driver=journald ...
    37  
    38  ## Note regarding container names
    39  
    40  The value logged in the `CONTAINER_NAME` field is the container name
    41  that was set at startup.  If you use `docker rename` to rename a
    42  container, the new name will not be reflected in the journal entries.
    43  Journal entries will continue to use the original name.
    44  
    45  ## Retrieving log messages with journalctl
    46  
    47  You can use the `journalctl` command to retrieve log messages.  You
    48  can apply filter expressions to limit the retrieved messages to a
    49  specific container.  For example, to retrieve all log messages from a
    50  container referenced by name:
    51  
    52      # journalctl CONTAINER_NAME=webserver
    53  
    54  You can make use of additional filters to further limit the messages
    55  retrieved.  For example, to see just those messages generated since
    56  the system last booted:
    57  
    58      # journalctl -b CONTAINER_NAME=webserver
    59  
    60  Or to retrieve log messages in JSON format with complete metadata:
    61  
    62      # journalctl -o json CONTAINER_NAME=webserver
    63  
    64  ## Retrieving log messages with the journal API
    65  
    66  This example uses the `systemd` Python module to retrieve container
    67  logs:
    68  
    69      import systemd.journal
    70  
    71      reader = systemd.journal.Reader()
    72      reader.add_match('CONTAINER_NAME=web')
    73  
    74      for msg in reader:
    75        print '{CONTAINER_ID_FULL}: {MESSAGE}'.format(**msg)
    76