Mention new logging configuration

source/Releases/Release-Galactic-Geochelone.rst

@@ -36,6 +36,18 @@ It is now possible to specify different logging levels for different loggers on
 The above command sets a global log level of WARN, but sets the log level of the talker node messages to DEBUG.
 The ``--log-level`` command-line option can be passed an arbitrary number of times to set different log levels for each logger.
 
+Ability to configure logging directory through environment variables
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+It is now possible to configure the logging directory through two environment variables: ``ROS_LOG_DIR`` and ``ROS_HOME``.
+The logic is as follows:
+
+* Use ``$ROS_LOG_DIR`` if ``ROS_LOG_DIR`` is set and not empty.
+* Otherwise, use ``$ROS_HOME/log``, using ``~/.ros`` for ``ROS_HOME`` if not set or if empty.
+
+Thus the default value stays the same: ``~/.ros/log``.
+
+Related PRs: `ros2/rcl_logging#53 <https://github.com/ros2/rcl_logging/pull/53>`_ and `ros2/launch#460 <https://github.com/ros2/launch/pull/460>`_.
 
 Changes since the Foxy release
 ------------------------------

source/Tutorials/Logging-and-logger-configuration.rst

@@ -19,6 +19,76 @@ Over time you will see output from various log calls with different properties.
 To start with you will only see output from log calls with severity ``INFO`` and above (``WARN``, ``ERROR``, ``FATAL``).
 Note that the first message will only be logged once, though the line is reached on each iteration, as that is a property of the log call used for that message.
 
+Logging directory configuration
+-------------------------------
+
+.. note::
+
+   The logging directory can only be configured starting in Galactic.
+
+The logging directory can be configured through two environment variables: ``ROS_LOG_DIR`` and ``ROS_HOME``.
+The logic is as follows:
+
+* Use ``$ROS_LOG_DIR`` if ``ROS_LOG_DIR`` is set and not empty.
+* Otherwise, use ``$ROS_HOME/log``, using ``~/.ros`` for ``ROS_HOME`` if not set or if empty.
+
+For example, to set the logging directory to ``~/my_logs``:
+
+.. tabs::
+
+  .. group-tab:: Linux
+
+    .. code-block:: bash
+
+      export ROS_LOG_DIR=~/my_logs
+      ros2 run logging_demo logging_demo_main
+
+  .. group-tab:: macOS
+
+    .. code-block:: bash
+
+      export ROS_LOG_DIR=~/my_logs
+      ros2 run logging_demo logging_demo_main
+
+  .. group-tab:: Windows
+
+    .. code-block:: bash
+
+      set "ROS_LOG_DIR=~/my_logs"
+      ros2 run logging_demo logging_demo_main
+
+You will then find the logs under ``~/my_logs/``.
+
+Alternatively, you can set ``ROS_HOME`` and the logging directory will be relative to it (``$ROS_HOME/log``).
+``ROS_HOME`` is intended to be used by anything that needs a base directory.
+Note that ``ROS_LOG_DIR`` has to be either unset or empty.
+For example, with ``ROS_HOME`` set to ``~/my_ros_home``:
+
+.. tabs::
+
+  .. group-tab:: Linux
+
+    .. code-block:: bash
+
+      export ROS_HOME=~/my_ros_home
+      ros2 run logging_demo logging_demo_main
+
+  .. group-tab:: macOS
+
+    .. code-block:: bash
+
+      export ROS_HOME=~/my_ros_home
+      ros2 run logging_demo logging_demo_main
+
+  .. group-tab:: Windows
+
+    .. code-block:: bash
+
+      set "ROS_HOME=~/my_ros_home"
+      ros2 run logging_demo logging_demo_main
+
+You will then find the logs under ``~/my_ros_home/log/``.
+
 Logger level configuration: programmatically
 --------------------------------------------