(logging-facility is available from 1.99.10 and onwards)
This chapter assumes familiarity with syslog, the unix logging device. PDNS logs messages with different levels. The more urgent the message, the lower the 'priority'. By default, PDNS will only log messages with an urgency of 3 or lower, but this can be changed using the loglevel setting in the configuration file. Setting it to 0 will eliminate all logging, 9 will log everything.
By default, logging is performed under the 'DAEMON' facility which is shared with lots of other programs. If you regard nameserving as important, you may want to have it under a dedicated facility so PDNS can log to its own files, and not clutter generic files.
For this purpose, syslog knows about 'local' facilities, numbered from LOCAL0 to LOCAL7. To move PDNS logging to LOCAL0, add logging-facility=0 to your configuration.
Furthermore, you may want to have separate files for the differing prioties - preventing lower priority messages from obscuring important ones.
A sample syslog.conf might be:
local0.info -/var/log/pdns.info local0.warn -/var/log/pdns.warn local0.err /var/log/pdns.err
Where local0.err would store the really important messages. For performance and diskspace reasons, it is advised to audit your syslog.conf for statements also logging PDNS activities. Many syslog.confs have a '*.*' statement to /var/log/syslog, which you may want to remove.
For performance reasons, be especially certain that no large amounts of synchronous logging take place. Under Linux, this is indicated by filenames not starting with a '-' - indicating a synchronous log, which hurts performance.
Be aware that syslog by default logs messages at the configured priority and higher! To log only info messages, use local0.=info.