WIP (add logging.md)

logging.md

@@ -3,3 +3,46 @@ layout: page
 title: Logging
 permalink: /logging/
 ---
+
+Radicale logs to ``stderr``. The verbosity of the log output can be controlled
+with ``--debug`` command line argument or the ``debug`` configuration option in
+the ``logging`` section.
+
+This is the recommended configuration for use with modern init systems
+(like **systemd**) or if you just test Radicale in a terminal.
+
+You can configure Radicale to write its logging output to files (and even
+rotate them).
+This is useful if the process daemonizes or if your chosen method of running
+Radicale doesn't handle logging output.
+
+A logging configuration file can be specified in the ``config`` configuration
+option in the ``logging`` section. The file format is explained in the
+[Python Logging Module](https://docs.python.org/3/library/logging.config.html#configuration-file-format).
+
+An example configuration to write the log output to the file */var/log/radicale/log*:
+```ini
+[loggers]
+keys = root
+
+[handlers]
+keys = file
+
+[formatters]
+keys = full
+
+[logger_root]
+level = WARNING  # Change this to DEBUG or INFO for higher verbosity.
+handlers = file
+
+[handler_file]
+class = FileHandler
+args = ('/var/log/radicale/log',)  # Specify the output file here.
+formatter = full
+
+[formatter_full]
+format = %(asctime)s - [%(thread)x] %(levelname)s: %(message)s
+```
+
+You can specify multiple **logger**, **handler** and **formatter** if you want
+to have multiple simultaneous log outputs.