logging {
[ channel channel_name {
( file path_name
[ versions ( number | unlimited ) ]
[ size size_spec ]
| syslog ( kern | user | mail | daemon | auth | syslog | lpr |
news | uucp | cron | authpriv | ftp |
local0 | local1 | local2 | local3 |
local4 | local5 | local6 | local7 )
| null );
[ severity ( critical | error | warning | notice |
info | debug [ level ] | dynamic ); ]
[ print-category yes_or_no; ]
[ print-severity yes_or_no; ]
[ print-time yes_or_no; ]
}; ]
[ category category_name {
channel_name; [ channel_name; ... ]
}; ]
...
};
The logging statement configures a wide variety of logging options for the nameserver. Its channel phrase associates output methods, format options, and severity levels with a name that you can then use with the category phrase to select how various classes of messages are logged.
You need only one logging statement to define as many channels and categories as you want. If there are multiple logging statements in a configuration file, the first defined statement determines the logging, and warnings are issued for the others. If there is no logging statement, the default logging configuration is as follows:
logging {
category default { default_syslog; default_debug; };
category panic { default_syslog; default_stderr; };
category packet { default_debug; };
category eventlib { default_debug; };
};
All log output goes to one or more channels; you can make as many of them as you want.
Every channel definition must include a clause that specifies whether messages selected for the channel go to a file, go to a particular syslog facility, or are discarded. It can optionally also limit the message severity level that will be accepted by the channel (default is info), and whether to include a time stamp generated by named, the category name, or severity level. The default is not to include anything.
The word null as the destination option for the channel will cause all messages sent to it to be discarded; other options for the channel are meaningless.
The file clause can include limitations both on how large the file is allowed to become, and how many versions of the file will be saved each time the file is opened.
The size option for files is simply a hard ceiling on log growth. If the file ever exceeds the size, named will not write anything more to it until the file is reopened; exceeding the size does not automatically trigger a reopen. The default is to not limit the size of the file.
If you use the version option, named will retain the specified number of backup versions of the file by renaming them when opening. For example, if you choose to keep three old versions of the file lamers.log, just before it is opened lamers.log.1 is renamed to lamers.log.2, lamers.log.0 is renamed to lamers.log.1, and lamers.log is renamed to lamers.log.0. No rolled versions are kept by default. The unlimited keyword is synonymous with 99 in current BIND releases.
The argument for the syslog clause is a syslog facility as described in the syslog reference page. How syslogd will handle messages sent to this facility is described in the syslog.conf reference page. If you have an old version of syslog that uses only two arguments to the openlog() function, this clause is silently ignored.
The severity clause works like syslog's priorities, except that they can also be used if you are writing straight to a file rather than using syslog. Messages that are not at least of the severity level given are not selected for the channel; messages of higher severity levels are accepted.
If you are using syslog, the syslog.conf priorities also determine what eventually passes through. For example, defining a channel facility and severity as daemon and debug but only logging daemon.warning via syslog.conf causes messages of severity info and notice to be dropped. If the situation were reversed, with named writing messages of only warning or higher, syslogd would print all messages it received from the channel.
The server can supply extensive debugging information when it is in debugging mode. If the server's global debug level is greater than zero, debugging mode will be active. The global debug level is set either by starting the server with the -d flag followed by a positive integer, or by sending the server the SIGUSR1 signal. The global debug level can be set to zero, and debugging mode turned off, by sending the server the SIGUSR2 signal. All debugging messages in the server have a debug level, and higher debug levels give more more detailed output. Channels that specify a specific debug severity will get debugging output of level 3 or less any time the server is in debugging mode, regardless of the global debugging level. For example:
channel specific_debug_level {
file "foo";
severity debug 3;
};
Channels with dynamic severity use the server's global level to determine what messages to print.
If print-time is turned on, the date and time are logged. The print-time option may be specified for a syslog channel, but is usually meaningless since syslog also prints the date and time. If print-category is requested, the category of the message will be logged as well. Finally, if print-severity is on, the severity level of the message will be logged. The print- options may be used in any combination, and will always be printed in the following order: time, category, severity. The following example shows the three print- options are on:
28-Apr-1997 15:05:32.863 default: notice: Ready to answer queries.
The following four predefined channels are used for named's default logging. See the category phrase section for a description on how to use them.
channel default_syslog {
syslog daemon; # send to syslog's daemon facility
severity info; # only send priority info and higher
};
channel default_debug {
file "named.run"; # write to named.run in the working directory
# Note: stderr is used instead of named.run
# if the server is started with the -f option.
severity dynamic; # log at the server's current debug level
};
channel default_stderr { # writes to stderr
file "<stderr>"; # this is illustrative only; there's currently
# no way of specifying an internal file
# descriptor in the configuration language.
severity info; # only send priority info and higher
};
channel null {
null; # toss anything sent to this channel
};
Once a channel is defined, it cannot be redefined. Thus you cannot alter the built-in channels directly, but you can modify the default logging by pointing categories at channels you have defined.
There are many categories, so you can send the logs you want to see wherever you want without seeing logs you do not want. If you do not specify a list of channels for a category, log messages in that category will be sent to the default category instead. If you do not specify a default category, the following is used:
category default { default_syslog; default_debug; };
As an example, if you want to log security events to a file, but you also want to keep the default logging behavior, you would specify the following:
channel my_security_channel {
file "my_security_file";
severity info;
};
category security { my_security_channel; default_syslog; default_debug; };
To discard all messages in a category, specify the null channel:
category lame-servers { null; };
category cname { null; };
The following categories are available:
category default { default_syslog; default_debug; };
category eventlib { default_debug; };
category panic { default_syslog; default_stderr; };