Older versions of ircd had no consistent way of logging various
actions.  Some things, such as G-lines, were written out to log files
with names compiled into the server.  Others could only be logged
through syslog.  Some required that their log files exist beforehand.
Starting with u2.10.11, this situation has changed dramatically.

All logging in the server is now unified through a single logging
subsystem.  Unfortunately, the server still does not generate all the
logs that it could, and some more tuning is in store for the next
major release of ircd.  Nevertheless, the logs that are generated are
far more consistent, and those log messages may be sent to a given
file, to syslog, or even to online operators--or any combination of
these three methods.  This file is intended to describe configuration
of the logging subsystem.

All logs are classified by a "subsystem" and a "level."  The subsystem
is a major classification; each subsystem may be configured
individually.  The level classification is used to indicate how
important the message is; subsystems may be configured to omit log
messages with less than a certain importance--not unlike syslog.

Levels

Levels are used to classify the importance of various log messages.
The most important level is the "CRIT" level; the least important is
the "DEBUG" level.  Each of the levels is also mapped to a
corresponding syslog level, and some may even force generation of
certain types of server notices.  Each importance level is described
below.

 * CRIT - Used for very critical notifications, such as server
   termination.  This is mapped to the corresponding "CRIT" syslog
   priority.  This will also generate server notices to the "OLDSNO"
   server notice mask.

 * ERROR - Used to report important error conditions.  This is mapped
   to the corresponding "ERR" syslog priority.

 * WARNING - Used to warn about certain conditions.  This is mapped to
   the corresponding "WARNING" syslog priority.

 * NOTICE - Used for reporting important information.  This is mapped
   to the corresponding "NOTICE" syslog priority.

 * TRACE - Used to tracing operation of the server.  This is mapped to
   the corresponding "INFO" syslog priority.

 * INFO - Used for reporting unimportant but potentially useful
   information.  This is mapped to the corresponding "INFO" syslog
   priority.

 * DEBUG - Used for reporting debugging information.  This is mapped
   to the corresponding "DEBUG" syslog priority.  This will also
   generate server notices to the "DEBUG" server notice mask.

Subsystems

All of the subsystems are described below, along with their default
logging configuration.  There are no default log files to log to, and
the default logging level is INFO (unless the server is compiled with
debugging enabled)--this means that only notices of importance INFO or
higher will be logged.

 * SYSTEM - Used to report information that affects the server as a
   whole.  By default, log messages to this subsystem go nowhere.

 * CONFIG - Used to report information concerning the configuration
   file.  By default, log messages to this subsystem go to the default
   syslog facility, which defaults to "USER," and to the "OLDSNO"
   server notice mask.

 * OPERMODE - Used to report usage of /OPMODE and /CLEARMODE.  By
   default, log messages to this subsystem go to the "HACK4" server
   notice mask.

 * GLINE - Used to report usage of /GLINE, particularly BADCHANs.  By
   default, log messages to this subsystem go to the "GLINE" server
   notice mask.

 * JUPE - Used to report usage of /JUPE.  By default, log messages to
   this subsystem go to the "NETWORK" server notice mask.

 * WHO - Used to report usage of the extended features of /WHO
   (/WHOX).  By default, log messages to this subsystem go nowhere.

 * NETWORK - Used to report net junctions and net breaks.  By default,
   log messages to this subsystem go to the "NETWORK" server notice
   mask.

 * OPERKILL - Used to report usage of /KILL by IRC operators.  By
   default, log messages to this subsystem go nowhere.

 * SERVKILL - Used to report usage of /KILL by other servers.  By
   default, log messages to this subsystem go nowhere.

 * USER - Used to report user sign-ons and sign-offs.  By default, log
   messages to this subsystem go nowhere.

 * OPER - Used to report usage of /OPER, either successfully or
   unsuccessfully.  By default, log messages to this subsystem go to
   the "OLDREALOP" server notice mask.

 * RESOLVER - Used to report error messages or other conditions from
   the resolver and authentication system.  By default, log messages
   to this subsystem go nowhere.

 * SOCKET - Used to report problems with sockets.  By default, log
   messages to this subsystem go nowhere.

 * IAUTH - Used to report connects, disconnects and errors for the
   IAuth authorization mechanism.  By default, log messages to this
   subsystem go to the "NETWORK" server notice mask.

 * DEBUG - Used only when debugging is enabled.  All log messages to
   this subsystem go either to the console or to the debug log file
   compiled into the server, as well as to the "DEBUG" server notice
   mask.  This is the only subsystem with a default log file.

Configuration

The true power of the logging subsystem comes from its extremely
flexible configuration.  The default server facility can be
configured, as can the facility for each individual subsystem
described above.  Moreover, administrators can configure the server to
log to specific files, send selected log messages to operators
subscribed to any server notice mask, and even change the default log
level for each subsystem.

The logging subsystem has a set of tables mapping names to the
numerical values used internally.  Subsystems, levels, syslog
facilities, and server notice masks are all configured using strings.
These tables even include special strings, such as "DEFAULT" and
"NONE."  Each possible configuration piece is described below.

Default Syslog Facility

The IRC server has a default facility that it uses when sending log
messages to syslog.  The default facility may be overridden for each
individual subsystem, but the default itself can be changed with an
appropriate Feature entry in the configuration file.  The facility
normally defaults to "USER," but may be configured to be any of AUTH,
CRON, DAEMON, LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6,
LOCAL7, LPR, MAIL, NEWS, USER, or UUCP.  Some systems also have the
AUTHPRIV facility.  To configure this default, add a Feature line to
the configuration file that looks like "LOG" = "<facility>";
<facility> should be replaced with the string for the desired default
syslog facility.

Log Files

Each subsystem may be configured to send its log messages to any
single log file with a Feature entry like "LOG" = "<subsys>" "FILE"
"<file>"; <subsys> should be replaced with one of the subsystem names
described above, and <file> should be a file name for the log file.
The file name may be relative to the server's data directory
("DPATH"), or it may be an absolute path name.  Note that if you're
using chroot, these absolute path names will be relative to the
server's root directory.

Logging to Syslog

By default, except for the CONFIG subsystem, no logs are sent to
syslog.  This can be overridden using an Feature entry like "LOG" =
"<subsys>" "FACILITY" "<facility>"; <subsys>, as above, should be
replaced with one of the subsystem names described above, and
<facility> must be one of the facility strings mentioned under
"Default Syslog Facility."  The facility string may also be "NONE," to
turn off syslog for that subsystem, and "DEFAULT," to use the server's
default facility.  Please don't confuse a DEFAULT facility with the
default for a particular subsystem; only the CONFIG subsystem defaults
to DEFAULT, whereas all the rest default to NONE.

Logging via Server Notices

Log messages can be sent to online IRC operators.  Many subsystems
actually default to this behavior, in fact.  For security, log
messages containing IP addresses or other extremely sensitive data
will never be sent via server notices, but all others can be sent to a
specific server notice mask.  (For more information about server
notice masks, please see doc/snomask.html.)  The available mask names
are OLDSNO, SERVKILL, OPERKILL, HACK2, HACK3, UNAUTH, TCPCOMMON,
TOOMANY, HACK4, GLINE, NETWORK, IPMISMATCH, THROTTLE, OLDREALOP,
CONNEXIT, and DEBUG.  The special mask name "NONE" inhibits sending of
server notices for a particular subsystem.  The Feature entry for this
configuration looks like "LOG" = "<subsys>" "SNOMASK" "<mask>"; again,
<subsys> is one of the subsystems described above, and <mask> is one
of the mask names.

Setting Minimum Logging Level

The minimum log level for a particular subsystem may be set with an
Feature entry like "LOG" = "<subsys>" "LEVEL" "<level>"; here,
<subsys> is yet again one of the subsystems described above, and
<level> is one of the level names, also described above.