syslogd.8   [plain text]


.\"Copyright (c) 2004-2008 Apple Inc. All rights reserved.
.\"
.\"@APPLE_LICENSE_HEADER_START@
.\"
.\"This file contains Original Code and/or Modifications of Original Code
.\"as defined in and that are subject to the Apple Public Source License
.\"Version 2.0 (the 'License'). You may not use this file except in
.\"compliance with the License. Please obtain a copy of the License at
.\"http://www.opensource.apple.com/apsl/ and read it before using this
.\"file.
.\"
.\"The Original Code and all software distributed under the License are
.\"distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
.\"EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
.\"INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
.\"FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
.\"Please see the License for the specific language governing rights and
.\"limitations under the License.
.\"
.\"@APPLE_LICENSE_HEADER_END@
.\"
.Dd October 18, 2004
.Dt SYSLOGD 8
.Os "Mac OS X"
.Sh NAME
.Nm syslogd
.Nd Apple System Log server
.Sh SYNOPSIS
.Nm
.Op Fl d
.Op Fl D
.Op Fl m Ar mark_interval
.Op Fl c Ar log_cutoff
.Op Fl l Ar lib_path
.Op Fl db_max Ar size
.Op Fl utmp_ttl Ar time
.Op Fl fs_ttl Ar time
.Op Fl mps_limit Ar quota
.Op Fl dup_delay Ar time
.Op Fl module_name Li {0|1}
.Sh DESCRIPTION
The
.Nm
server receives and processes log messages.
Several modules receive input messages through various channels,
including UNIX domain sockets associated with the
.Xr syslog 3 ,
.Xr asl 3 ,
and kernel printf APIs, 
and optionally on a UDP socket from network clients.
.Pp
The Apple System Log facility comprises the 
.Xr asl 3
API, a new 
.Nm
server, the
.Xr syslog 1
command-line utility, and a data store file manager,
.Xr aslmanager 8 .
The system supports structured and extensible messages, 
permitting advanced message browsing and management through search APIs and
other components of the Apple system log facility.
.Pp
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 searching.
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.
.Pp
The following options are recognized:
.Bl -tag -width "-dup_delay"
.It Fl d
Run
.Nm
in debugging mode.
The server stays attached to the controlling terminal and prints debugging messages.
.It Fl D
Start as a daemon.
This option forces 
.Nm
to fork and have the child process become a daemon.
Since
.Nm
is started by
.Nm launchd ,
this is not normally required.
.It Fl m
Set the number of minutes between
.Dq mark
messages.
Mark messages are normally disabled.
If
.Fl m
is specified with no arguments, mark messages will be written every 20 minutes.
The 
.Dq mark
facility is disabled if the setting is zero minutes.
.It Fl c
Sets a cutoff filter for log priorities for messages to be retained in the log message data store.
The value of 
.Ar log_cutoff
must be between 0 and 7, corresponding to log priorities LOG_EMERG or ASL_LEVEL_EMERG
and LOG_DEBUG or ASL_LEVEL_DEBUG as defined in the 
.Xr syslog 3
and
.Xr asl 3
header files.
Received messages with a priority or level value greater than the cutoff will not be saved in the data store.
The default filter value is set to allow all message priorities.
Message filtering is primarily specified by the rules in the /etc/asl.conf file.
However, if there are no matching rules for the ASL data store in the asl.conf file,
then all messages that are allowed by the cutoff filter are saved.
.Pp
Note that a this filter value may be adjusted while
.Nm
is running using the
.Nm syslog
command-line utility.
See the
.Xr syslog 1
manual.
The filter may be adjusted using the
.Dq -c
option.
.It Fl l
Specifies an alternate path for loading plug-in modules.
By default,
.Nm
checks for plug-in modules in the directory /usr/lib/asl.
.It Fl db_max
Sets the size limit in bytes for individual files in the data store.
The default value for
.Fl db_max
is 25600000 bytes.
Files are closed upon reaching the maximum size, and a new file is opened for subsequent messages.
.It Fl utmp_ttl
Sets the time-to-live in seconds for messages used by the
.Xr utmp ,
.Xr wtmp ,
and
.Xr lastlog
subsystems.
The default is 31622400 seconds (approximately 1 year).
Note that if archival is enabled (see the
.Xr 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.
.It Fl fs_ttl
Sets the time-to-live in seconds for filesystem error messages generated by the kernel.
The default is 31622400 seconds (approximately 1 year).
As in the case of
.Fl utmp_ttl ,
if archival is enabled, 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.
.It Fl mps_limit
Sets the per-process quota for messages per second allowed by
.Nm .
Any messages in excess of the quota limit from any process are ignored.
An error message is logged on behalf of the limited process, stating that its 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.
.It Fl dup_delay
Sets the time to delay for coalescing duplicate message in log files.
If a process logs multiple messages with the same text,
.Nm
will wait for the specified period of time to coalesce duplicates.
If identical messages arrive during this interval,
.Nm
will print a message of the form:
.Pp
.Li		May  7 12:34:56: --- last message repeated 17 times ---
.Pp
The default delay time is 30 seconds.
Setting the value to 0 disables the coalescing mechanism.
.El
.Pp
The remaining options of the form
.Fl module_name Li {0|1}
may be used to disable (0) or enable (1) the action of several of
.Mn 's
internal modules.
.Bl -tag -width "-asl_action"
.It Fl asl_in
The 
.Dq asl_in
module receives log messages on the UNIX domain socket associated with the 
.Xr asl 3
API.
The module may be disabled using
.Fl asl_in Li 0 .
The module is normally enabled.
.It Fl asl_action
The 
.Dq 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 
.Xr asl.conf 5
for details.
.It Fl klog_in
The 
.Dq klog_in
module receives log messages on the UNIX domain socket associated with the kernel logging API.
The module may be disabled using
.Fl klog_in Li 0 .
The module is normally enabled.
.It Fl bsd_in
The 
.Dq bsd_in
module receives log messages on the UNIX domain socket associated with the 
.Xr syslog 3
API.
The module may be disabled using
.Fl bsd_in Li 0 .
The module is normally enabled.
.It Fl bsd_out
The 
.Dq 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 
.Xr syslog.conf 5
for details.
This module exists for backward compatibility with previous
.Nm
implementations.
Apple encourages use of the
.Xr syslog 1
and
.Xr 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 
.Dq bsd_out
module to the 
.Dq asl_action
module.
.It Fl udp_in
The 
.Dq udp_in
module receives log messages on the UDP socket associated with the Internet syslog message protocol.
.Pp
This module is normally enabled, but is inactive.
The actual UDP sockets are managed by
.Nm launched ,
and configured in the
.Nm syslogd
configuration file /System/Library/LaunchDaemons/com.apple.syslogd.plist.
In the default configuration, 
.Nm launchd
does not open any sockets for the
.Dq syslog
UDP service, so no sockets are provided to the
.Dq udp_in 
module.
If no sockets are provided, the module remains inactive.
.Pp
The module may be specifically disabled using the
.Fl udp_in Li 0 
option.
.El
.Pp
.Nm
reinitializes in response to a HUP signal.
.Sh MESSAGE EXPIRY AND ARCHIVAL
.Nm
periodically invokes the
.Nm 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
.Xr aslmanager 8
manual for details.
.Nm
invokes
.Nm aslmanager
shortly after it starts up, at midnight local time if it is running,
and any time that a data store file reaches the
.Fl db_max
size limit.
.Sh 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
.Xr 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.
.Pp
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".
.Sh FILES
.Bl -tag -width /var/log/asl.archive -compact
.It Pa /etc/syslog.conf
bsd_out module configuration file
.It Pa /etc/asl.conf
asl_action module configuration file
.It Pa /var/run/syslog.pid
process ID file
.It Pa /var/run/log
name of the
.Ux
domain datagram log socket
.It Pa /dev/klog
kernel log device
.It Pa /var/log/asl
data store directory
.It Pa /var/log/asl.archive
default archive directory
.El
.Sh SEE ALSO
.Xr syslog 1 ,
.Xr logger 1 ,
.Xr asl 3 ,
.Xr syslog 3 ,
.Xr asl.conf 5
.Xr syslog.conf 5
.Sh HISTORY
The
.Nm
utility appeared in
.Bx 4.3 .
.Pp
The Apple System Log facility was introduced in Mac OS X 10.4.