Initial commit

vendor/github.com/hyperhq/hypercli/docs/admin/logging/journald.md

@@ -0,0 +1,92 @@
+<!--[metadata]>
++++
+aliases = ["/engine/reference/logging/journald/"]
+title = "journald logging driver"
+description = "Describes how to use the fluentd logging driver."
+keywords = ["Fluentd, docker, logging, driver"]
+[menu.main]
+parent = "smn_logging"
+weight = 2
++++
+<![end-metadata]-->
+
+# Journald logging driver
+
+The `journald` logging driver sends container logs to the [systemd
+journal](http://www.freedesktop.org/software/systemd/man/systemd-journald.service.html).  Log entries can be retrieved using the `journalctl`
+command, through use of the journal API, or using the `docker logs` command.
+
+In addition to the text of the log message itself, the `journald` log
+driver stores the following metadata in the journal with each message:
+
+| Field               | Description |
+----------------------|-------------|
+| `CONTAINER_ID`      | The container ID truncated to 12 characters. |
+| `CONTAINER_ID_FULL` | The full 64-character container ID. |
+| `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. |
+| `CONTAINER_TAG`     | The container tag ([log tag option documentation](log_tags.md)). |
+
+## Usage
+
+You can configure the default logging driver by passing the
+`--log-driver` option to the Docker daemon:
+
+    docker daemon --log-driver=journald
+
+You can set the logging driver for a specific container by using the
+`--log-driver` option to `docker run`:
+
+    docker run --log-driver=journald ...
+
+## Options
+
+Users can use the `--log-opt NAME=VALUE` flag to specify additional
+journald logging driver options.
+
+### tag
+
+Specify template to set `CONTAINER_TAG` value in journald logs. Refer to
+[log tag option documentation](log_tags.md) for customizing the log tag format.
+
+### labels and env
+
+The `labels` and `env` options each take a comma-separated list of keys. If there is collision between `label` and `env` keys, the value of the `env` takes precedence. Both options add additional metadata in the journal with each message.
+
+## Note regarding container names
+
+The value logged in the `CONTAINER_NAME` field is the container name
+that was set at startup.  If you use `docker rename` to rename a
+container, the new name will not be reflected in the journal entries.
+Journal entries will continue to use the original name.
+
+## Retrieving log messages with journalctl
+
+You can use the `journalctl` command to retrieve log messages.  You
+can apply filter expressions to limit the retrieved messages to a
+specific container.  For example, to retrieve all log messages from a
+container referenced by name:
+
+    # journalctl CONTAINER_NAME=webserver
+
+You can make use of additional filters to further limit the messages
+retrieved.  For example, to see just those messages generated since
+the system last booted:
+
+    # journalctl -b CONTAINER_NAME=webserver
+
+Or to retrieve log messages in JSON format with complete metadata:
+
+    # journalctl -o json CONTAINER_NAME=webserver
+
+## Retrieving log messages with the journal API
+
+This example uses the `systemd` Python module to retrieve container
+logs:
+
+    import systemd.journal
+
+    reader = systemd.journal.Reader()
+    reader.add_match('CONTAINER_NAME=web')
+
+    for msg in reader:
+      print '{CONTAINER_ID_FULL}: {MESSAGE}'.format(**msg)