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While BIND sends all logging to the UNIX sislog facility by default, as discussed later in the lesson where to start trouble shooting BIND, it is also possible to control BIND logging in a more granular fashion. You can direct events to the sislog, other log files, the STDERR facility, which is the system console by default or null which discards logs. BIND logging has two essential definitions - a channel and a category. A channel defines a location where log events are sent. A category is a type of log event; by placing a channel in a category phrase, the specified category's events are sent to the specified channel. Logging is configured through the logging statement in the named.conf file. Open your named.conf file in the text editor; start a logging statement followed by an open brace, on the next line you can first begin your first channel. 4 channels are defined by default: null which discards the log events, default_sislog which sends log entries to the sislog, default_debug which sends log entries to a file named named.run in the working directory, and default_stderr which sends log entries to STDERR. You can add your own channel by adding a channel phrase. Type channel, followed by an arbitrary channel name in quotes, and an open brace. The first option in the channel phrase should define where the channel points. This can be file followed by a file name in quotes sislog domain, STDERR or null. The file option can also have two other options: versions and size. Size controls how large the log file is allowed to grow and versions determines how many log files are kept when they surpass the size value. If size is not set and versions is, a new log file is created each time BIND starts and versions controls how many are kept. Versions can also be set to unlimited. If you specify a size value, versions must also be specified, or BIND will stop logging when the file reaches a specified size. If your channel is writing to a file, you will probably want to add the print-time yes, and the print-category yes options. This makes the time and category of each log entry record in the file; we can also specify print-severity yes if you want the severity level logged as well. Print-time isn't used with sislog, as sislog prints a time with each entry by default. A channel can also have a severity option, which defines the minimum severity level at which events must be to be logged to the channel. The default is info; remember to end the channel phrase with a close brace and semicolon. Next you need to specify category phrase; type category followed by the category for which to set logging. A list of these categories can be found in the BIND9 administrator's reference manual. Some examples of categories are default, general, security and update. Following the categories an open brace, the name of the channel to which to log followed by a semicolon, followed by a close brace and another semicolon. You can list multiple channels in the category phrase as long as each is followed by a semicolon. Events for the specified category will go to each of the specified channels. Once you have configured all the channels and categories you need, close the logging statement with a close brace and semicolon.