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SYSLOGD(8)                BSD System Manager's Manual               SYSLOGD(8)

NAME
     syslogd -- Apple System Log server

SYNOPSIS
     syslogd [-d] [-D] [-m mark_interval] [-l lib_path] [-db_max size] [-utmp_ttl time] [-mps_limit quota]
             [-dup_delay time] [-module_name {0|1}]

DESCRIPTION
     The syslogd server receives and processes log messages.  Several modules receive input messages through
     various channels, including UNIX domain sockets associated with the syslog(3), asl(3), and kernel
     printf APIs, and optionally on a UDP socket from network clients.

     The Apple System Log facility comprises the asl(3) API, a new syslogd server, the syslog(1) command-line commandline
     line utility, and a data store file manager, aslmanager(8).  The system supports structured and exten-sible extensible
     sible messages, permitting advanced message browsing and management through search APIs and other com-ponents components
     ponents of the Apple system log facility.

     Log messages are retained in a data store, subject to automatic archival, and input filtering as
     described below, to simplify the task of locating log messages and to facilitate browsing and search-ing. searching.
     ing.  The data store is intended to become a replacement for the numerous log files that are currently
     found in various locations on the system.  Those files will be phased out in future versions of Mac OS.

     The following options are recognized:

     -d          Run syslogd in debugging mode.  The server stays attached to the controlling terminal and
                 prints debugging messages.

     -D          Start as a daemon.  This option forces syslogd to fork and have the child process become a
                 daemon.  Since syslogd is started by launchd, this is not normally required.

     -m          Set the number of minutes between ``mark'' messages.  Mark messages are normally disabled.
                 If -m is specified with no arguments, mark messages will be written every 20 minutes.  The
                 ``mark'' facility is disabled if the setting is zero minutes.

     -db_max     Sets the size limit in bytes for individual files in the data store.  The default value for
                 -db_max is 25600000 bytes.  Files are closed upon reaching the maximum size, and a new file
                 is opened for subsequent messages.

     -utmp_ttl   Sets the time-to-live in seconds for messages used by the utmp, wtmp, and lastlog subsys-tems. subsystems.
                 tems.  The default is 31622400 seconds (approximately 1 year).  Note that if archival is
                 enabled (see the aslmanager(8) manual), these messages will be copied to an archive after
                 the regular time-to-live interval, but will persist in the data store until their own
                 expiry time.

     -mps_limit  Sets the kernel quota for messages per second allowed by syslogd.  Any messages in excess
                 of the quota limit from any process are ignored.  An error message is logged stating that
                 the kernel message quota has been exceeded, and that remaining messages for the current
                 second will be discarded.  The default limit is 500 messages per second per process.  A
                 value of 0 turns off the quota mechanism.

                 Note that this setting only limits the number of kernel messages that will be saved by
                 syslogd.  User processes are limited to 36000 messages per hour.  The limit for a user
                 process is not enforced if a remote-control ASL filter is in place for the process.

     -dup_delay  Sets the time to delay for coalescing duplicate message in log files.  If a process logs
                 multiple messages with the same text, syslogd will wait for the specified period of time to
                 coalesce duplicates.  If identical messages arrive during this interval, syslogd will print
                 a message of the form:

                      May 7 12:34:56: --- last message repeated 17 times ---The --The

                 The default delay time is 30 seconds.  Setting the value to 0 disables the coalescing mech-anism. mechanism.
                 anism.

     The remaining options of the form -module_name {0|1} may be used to disable (0) or enable (1) the
     action of several of internal modules.

     -asl_in      The ``asl_in'' module receives log messages on the UNIX domain socket associated with the
                  asl(3) API.  The module may be disabled using -asl_in 0.  The module is normally enabled.

     -asl_action  The ``asl_action'' module examines the stream of received log messages and acts upon them
                  according to the rules specified in the file /etc/asl.conf.  See asl.conf(5) for details.

     -klog_in     The ``klog_in'' module receives log messages on the UNIX domain socket associated with the
                  kernel logging API.  The module may be disabled using -klog_in 0.  The module is normally
                  enabled.

     -bsd_in      The ``bsd_in'' module receives log messages on the UNIX domain socket associated with the
                  syslog(3) API.  The module may be disabled using -bsd_in 0.  The module is normally
                  enabled.

     -bsd_out     The ``bsd_out'' module examines the stream of received log messages and acts upon them
                  according to the rules specified in the file /etc/syslog.conf.  See syslog.conf(5) for
                  details.  This module exists for backward compatibility with previous syslogd implementa-tions. implementations.
                  tions.  Apple encourages use of the syslog(1) and asl(3) search APIs over the use of the
                  log files that are specified in the /etc/syslog.conf file.  Future versions of Mac OS will
                  move functions that are currently handled by the ``bsd_out'' module to the ``asl_action''
                  module.

     -udp_in      The ``udp_in'' module receives log messages on the UDP socket associated with the Internet
                  syslog message protocol.

                  This module is normally enabled, but is inactive.  The actual UDP sockets are managed by
                  launchd, and configured in the syslogd configuration file /System/Library/LaunchDae-mons/com.apple.syslogd.plist. /System/Library/LaunchDaemons/com.apple.syslogd.plist.
                  mons/com.apple.syslogd.plist.  In the default configuration, launchd does not open any
                  sockets for the ``syslog'' UDP service, so no sockets are provided to the ``udp_in'' mod-ule. module.
                  ule.  If no sockets are provided, the module remains inactive.  A socket may be specified
                  by adding the following entry to the ``Sockets'' dictionary in the com.apple.syslogd.plist
                  file.

                             <key>NetworkListener</key>
                             <dict>
                                  <key>SockServiceName</key>
                                  <string>syslog</string>
                                  <key>SockType</key>
                                  <string>dgram</string>
                             </dict>

                  The module may be specifically disabled using the -udp_in 0 option.

     syslogd reinitializes in response to a HUP signal.

MESSAGE EXPIRY AND ARCHIVAL
     syslogd periodically invokes the aslmanager utility, which manages files in the ASL data store.  Files
     are removed or optionally copied to an archival directory after a (default) 2 day time-to-live.  See
     the aslmanager(8) manual for details.  syslogd invokes aslmanager shortly after it starts up, at mid-night midnight
     night local time if it is running, and any time that a data store file reaches the -db_max size limit.

DATA STORE SECURITY
     Messages saved in the ASL message store are written to files in /var/log/asl.  The message files are
     given read access controls corresponding to the read UID and GID specified in the messages themselves.
     Read access UID and GID settings may be attached to messages using the asl(3) library by setting a
     value for the "ReadUID" and/or "ReadGID" message keys.  The file permissions prevent access-controlled
     messages from being read by unauthorized users.

     Although clients are generally free to use any value for the "Facility" message key, only processes
     running with UID 0 may log messages with a facility value of "com.apple.system", or with a value that
     has "com.apple.system" as a prefix.  Messages logged by non UID 0 processes that use "com.apple.system"
     as a facility value or prefix will be saved with the facility value "user".

FILES
     /etc/syslog.conf      bsd_out module configuration file
     /etc/asl.conf         asl_action module configuration file
     /var/run/syslog.pid   process ID file
     /var/run/syslog       name of the UNIX domain datagram log socket
     /dev/klog             kernel log device
     /var/log/asl          data store directory
     /var/log/asl.archive  default archive directory
     /System/Library/LaunchDaemons/com.apple.syslogd.plist
                           launchd configuration file for syslogd

SEE ALSO
     syslog(1), logger(1), asl(3), syslog(3), asl.conf (5) syslog.conf (5)

HISTORY
     The syslogd utility appeared in 4.3BSD.

     The Apple System Log facility was introduced in Mac OS X 10.4.

Mac OS X                       October 18, 2004                       Mac OS X