570 lines
19 KiB
Groff
570 lines
19 KiB
Groff
.\" syslog.conf - syslogd(8) configuration file -*- nroff -*-
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.\" Copyright (c) 1995-2009 Martin Schulze <joey@infodrom.org>
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.\" Copyright (c) 2018-2019 Joachim Nilsson <troglobit@gmail.com>
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.\"
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.\" This file is part of the sysklogd package, a kernel and system log daemon.
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.\"
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.\" This program is free software; you can redistribute it and/or modify
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.\" it under the terms of the GNU General Public License as published by
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.\" the Free Software Foundation; either version 2 of the License, or
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.\" (at your option) any later version.
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.\"
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.\" This program is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public License
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.\" along with this program; if not, write to the Free Software
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.\" Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
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.\"
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.Dd Oct 30, 2019
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.Dt syslog.conf 5
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.Os "sysklogd (2.0)"
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.Sh NAME
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.Nm syslog.conf
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.Nd configuration file for syslogd
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.Sh DESCRIPTION
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The
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.Nm
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file is the main configuration file for
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.Xr syslogd 8
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which logs system messages on UNIX like systems. This file specifies
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rules for logging. For special features see the
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.Xr syslogd 8
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man page.
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.Pp
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Every rule has at least two fields, a
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.Em selector
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field and an
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.Em action .
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They may also have an
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.Em option
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field for a setting that applies only to that rule. Fields are
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separated by one or more spaces or tabs. A rule may be divided into
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several lines if the leading line ends with a single backslash ('\\')
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character.
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.Bd -literal -offset indent
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RULE := SELECTOR ACTION [;OPTION]
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SELECTOR := [SELECTOR;]facility[,facility].[!=]severity
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ACTION := /path/to/file
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|= |/path/to/named/pipe
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|= @remote[.host.tld][:PORT]
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OPTION := [OPTION,]
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|= RFC3164
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|= RFC5424
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|= rotate=SIZE:COUNT
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.Ed
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.Pp
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The
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.Em selector
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field specifies a pattern of facilities and priorities belonging to the
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specified action. The
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.Em action
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details where or what to do with the selected input. The
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.Em option
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field, which must start with the semi-colon option delimiter (';'),
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currently supports log formattaing and log rotation. The default log
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format is the traditional RFC3164 (included here for completeness),
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.Sy except
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for remote syslog targets where the BSD format (without both timestamp
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and hostname) is the default. The user must excplicitly set RFC3164 on
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a remote logging target. RFC5424 is the newest format with RFC3339 time
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stamps, msgid, structured data, and more. The BSD format cannot be set,
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it is only the default for remote targets for compatibility reasons.
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.Pp
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.Bl -tag -compact -width "RFC3164:"
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.It BSD:
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.Cm myproc[8710]: Kilroy was here.
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.It RFC3164:
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.Cm Aug 24 05:14:15 192.0.2.1 myproc[8710]: Kilroy was here.
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.It RFC5424:
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.Cm 2003-08-24T05:14:15.000003-07:00 192.0.2.1 myproc 8710 - - Kilroy was here.
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.El
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.Pp
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The log rotation, which is only relevant for files, details the max
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.Ar SIZE:COUNT
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a file can reach before it is rotated, and later compressed. This
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feature is mostly intended for embedded systems that do not want to have
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cron or a separate log rotate daemon.
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.Pp
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Comments, lines starting with a hash mark ('#'), and empty lines are
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ignored. If an error occurs during parsing the whole line is ignored.
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The configuration file can also include other files. The example
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.Pa /etc/syslog.conf
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has the following at the end:
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.Bd -literal -offset indent
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#
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# Drop your subsystem .conf file in /etc/syslog.d/
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#
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include /etc/syslog.d/*.conf
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.Ed
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.Sh SELECTORS
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The selector field consists of two parts, a
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.Em facility
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and a
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.Em priority ,
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separated by a period ('.'). Both parts are case insensitive and can
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also be specified as decimal numbers corresponding to the definitions in
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.Pa /usr/include/syslog.h .
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It is safer to use symbolic names rather than decimal numbers. Both
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facilities and priorities are described in
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.Xr syslogp 3 .
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The names mentioned below correspond to the similar
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.Ql LOG_FOO
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values in
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.Pa /usr/include/syslog.h .
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.Pp
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The
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.Em facility
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is one of the following keywords:
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.Bl -column "Code" "Facility" "Description" -offset indent
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.It Sy "Code" Ta Sy "Facility" Ta Sy "Description"
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.It 0 Ta kern Ta Kernel log messages
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.It 1 Ta user Ta User-level messages
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.It 2 Ta mail Ta Mail system
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.It 3 Ta daemon Ta General system daemons
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.It 4 Ta auth Ta Security/authorization messages
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.It 5 Ta syslog Ta Messages generated by syslogd
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.It 6 Ta lpr Ta Line printer subystem
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.It 7 Ta news Ta Network news subsystem
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.It 8 Ta uucp Ta UNIX-to-UNIX copy
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.It 9 Ta cron Ta Clock/cron daemon (BSD, Linux)
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.It 10 Ta authpriv Ta Security/authorization messages (private)
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.It 11 Ta ftp Ta FTP daemon
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.It 12 Ta ntp Ta NTP subsystem
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.It 13 Ta security Ta Log audit
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.It 14 Ta console Ta Log alert
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.It 15 Ta unused Ta Clock/cron daemon (Solaris)
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.It 16 Ta local0 Ta Reserved for local/system use
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.It 17 Ta local1 Ta Reserved for local/system use
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.It 18 Ta local2 Ta Reserved for local/system use
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.It 19 Ta local3 Ta Reserved for local/system use
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.It 20 Ta local4 Ta Reserved for local/system use
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.It 21 Ta local5 Ta Reserved for local/system use
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.It 22 Ta local6 Ta Reserved for local/system use
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.It 23 Ta local7 Ta Reserved for local/system use
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.El
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.Pp
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Notice, several of the above listed facilities are not supported
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by the standard C library (GLIBC, musl libc, or uClibc) on Linux.
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The
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.Lb libsyslog
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shipped with
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.Nm sysklogd ,
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however, supports all the above facilities in full. Also, the keyword
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.Ql mark
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is only for internal use and should therefore not be used in
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applications. The
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.Em facility
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specifies the subsystem that produced the message, e.g. all mail
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programs log with the mail facility,
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.Ql LOG_MAIL ,
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if they log using syslog.
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.Pp
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In most cases anyone can log to any facility, so we rely on convention
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for the correct facility to be chosen. However, generally only the
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kernel can log to the
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.Ql kern
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facility. This because the implementation of
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.Xr openlog 3
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and
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.Xr syslog 3
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in GLIBC does not allow logging to the
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.Ql kern
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facility.
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.Xr klogd 8
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circumvents this restriction when logging to
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.Xr syslogd 8
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by using the
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.Lb libsyslog
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.Pp
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The
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.I priority
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is one of the following keywords, in ascending order:
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.Bl -column "Code" "Facility" "Description" -offset indent
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.It Sy "Value" Ta Sy "Severity" Ta Sy "Description"
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.It 0 Ta emergency Ta System is unusable
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.It 1 Ta alert Ta Action must be taken immediately
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.It 2 Ta critical Ta Critical condtions
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.It 3 Ta error Ta Error conditions
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.It 4 Ta warning Ta Warning conditions
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.It 5 Ta notice Ta Normal but significal conditions
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.It 6 Ta info Ta Informational messages
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.It 7 Ta debug Ta Debug-level messages
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.El
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.Pp
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The default log level of most applications is
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.Ql notice ,
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meaning only
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.Ql notice
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and above are forwarded to
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.Nm syslogd .
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See
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.Xr setlogmask 3
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for more information on how to change the default log level of your
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application.
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.Pp
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In addition to the above mentioned facility and priority names,
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.Xr syslogd 8
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understands the following extensions:
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.Pp
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.Bl -tag -compact -width "'none'"
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.It *
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An asterisk ('*') matches all facilities or all priorities, depending on
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where it is used (before or after the period).
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.It none
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The keyword
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.Ql none
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stands for no priority of the given facility.
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.It ,
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Multiple facilities may be specified for a single priority pattern in
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one statement using the comma (',') operator to separate the facilities.
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You may specify as many facilities as you want. Please note that only
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the facility part from such a statement is taken, a priority part would
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be ignored.
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.It ;
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Multiple selectors may be specified for a single
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.Em action
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using the semicolon (';') separator. Selectors are processed from left
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to right, with each selector being able to overwrite preceding ones.
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Using this behavior you are able to exclude some priorities from the
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pattern.
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.It =
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This version of
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.Xr syslogd 8
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has a syntax extension to the original BSD source, which makes its use
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more intuitive. You may precede every priority with an equation sign
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('=') to specify that only this single priority should be matched,
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instead of the default: this priority and all higher priorities.
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.It !
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You may also precide the priority with an exclamation mark ('!') if you
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want to ignore this priority and all higher priorities. You may even
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use both the exclamation mark and the equation sign if you want to
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ignore a single priority. If both extensions are used, the exclamation
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mark must occur before the equation sign.
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.El
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.Sh ACTIONS
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The action field of a rule is the destination or target for a match. It
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can be a file, a UNIX named pipe, the console, or a remote machine.
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.Ss Regular File
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Typically messages are logged to real files. The filename is specified
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with an absolute pathname.
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.Pp
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You may prefix each entry with a minus sign ('-') to avoid syncing the
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file after each log message. Note that you might lose information if
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the system crashes right after a write attempt. Nevertheless this might
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give you back some performance, especially if you run programs that use
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logging in a very verbose manner.
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.Ss Named Pipes
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This version of
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.Xr syslogd 8
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supports logging to named pipes (FIFOs). A FIFO, or named pipe, can be
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used as a destination for log messages by prepending a pipe symbol ('|')
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to the name of the file. This can be very handy for debugging. Note
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that the FIFO must be created with the
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.Xr mkfifo 1
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command before
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.Nm syslogd
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is started.
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.Ss Terminal and Console
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If the file you specified is a tty, special tty-handling is done, same
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with
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.Pa /dev/console .
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.Ss Remote Machine
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Full remote logging support is available in
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.Nm syslogd ,
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i.e. to send messages to a remote syslog server, and and to receive
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messages from remote hosts. To forward messages to another host,
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prepend the hostname with the at sign ('@'). If a port number is added
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after a colon (':') then that port will be used as the destination port
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rather than the usual syslog port.
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.Pp
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This feature makes it possible to collect all syslog messages in a
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network on a central host. This reduces administration needs and
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can be really helpful when debugging distributed systems.
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.Pp
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Using a named pipe log method, messages from remote hosts can be sent to
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a log program. By reading log messages line by line such a program is
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able to sort log messages by host name or program name on the central
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log host. This way it is possible to split the log into separate files.
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.Pp
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By default messages to remote remote hosts were formatted in the original
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BSD style, without timestamp or hostname. As of
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.Nm syslogd
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v2.0 the default includes timstamp and hostname. It is also possible to
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enable the new RFC5424 style formatting, append ';RFC5424' after the
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hostname.
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.Ss List of Users
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Usually critical messages are also directed to
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.Ql root
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on that machine. You can specify a list of users that ought to receive
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the log message on their terminal by writing their usernames. You may
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specify more than one user by separating the usernames with commas
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(','). Only logged in users will receive the log messages.
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.Ss Everyone logged on
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Emergency messages often go to all users currently online to notify them
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that something strange is happening with the system. To specify this
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.Xr wall 1
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feature use an asterisk ('*').
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.Sh EXAMPLES
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This section lists some examples, partially from actual site setups.
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.Ss Catch Everything
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This example matches all facilities and priorities and stores everything
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in the file
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.Pa /var/log/syslog
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in RFC5424 format. Every time the file reaches 10 MiB it is rotated and
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five files in total are kept, including the non-rotated file.
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.Bd -literal -offset indent
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# Match all log messages, store in RC5424 format and rotate every 10 MiB
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#
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*.* /var/log/critical ;rotate=10M:5,RFC5424
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.Ed
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.Ss Critical
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This stores all messages of priority
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.Ql crit
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in the file
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.Pa /var/log/critical ,
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with the exception of any kernel messages.
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.Bd -literal -offset indent
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# Store critical stuff in critical
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#
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*.=crit;kern.none /var/log/critical
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.Ed
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.Ss Kernel
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This is an example of the 2nd selector overwriting part of the first
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one. The first selector selects kernel messages of priority
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.Ql info
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and higher. The second selector filters out kernel messages of priority
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.Ql error
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and higher. This leaves just priorities
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.Ql info ,
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.Ql notice ,
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and
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.Ql warning
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to get logged.
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.Bd -literal -offset indent
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# Kernel messages are stored in the kernel file, critical messages and
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# higher ones also go to another host and to the console
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#
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kern.* /var/log/kernel
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kern.crit @finlandia ;RFC5424
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kern.crit /dev/console
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kern.info;kern.!err /var/log/kernel.info
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.Ed
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.Pp
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The first rule directs any message that has the kernel facility to the
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file
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.Pa /var/log/kernel .
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Recall that only the kernel itself can log to this facility.
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.Pp
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The second statement directs all kernel messages of priority
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.Ql crit
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and higher to the remote host
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.Ql finlandia
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in RFC5424 style formatting. This is useful, because if the host
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crashes and the disks get irreparable errors you might not be able to
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read the stored messages. If they're on a remote host, too, you still
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can try to find out the reason for the crash.
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.Pp
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The third rule directs kernel messages of priority
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.Ql crit
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and higher to the actual console, so the person who works on the machine
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will get them, too.
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.Pp
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The fourth line tells
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.Nm syslogd
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to save all kernel messages that come with priorities from
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.Ql info
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up to
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.Ql warning
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in the file
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.Pa /var/log/kernel.info .
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.Ss Redirecting to a TTY
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This directs all messages that use
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.Ql mail.info
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(in source
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.Ql LOG_MAIL | LOG_INFO )
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to
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.IR /dev/tty12 ,
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the 12th console. For example the tcpwrapper
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.BR tcpd (8)
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uses this as its default.
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.Bd -literal -offset indent
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# The tcp wrapper logs with mail.info, we display
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# all the connections on tty12
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#
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mail.=info /dev/tty12
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.Ed
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.Ss Redirecting to a file
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This pattern matches all messages that come with the
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.Ql mail
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facility, except for the
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.Ql info
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priority. These will be stored in the file
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.Pa /var/log/mail .
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.Bd -literal -offset indent
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# Write all mail related logs to a file
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#
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mail.*;mail.!=info /var/log/mail
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.Ed
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.Ss Single Priority from Two Facilities
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This will extract all messages that come either with
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.Ql mail.info
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or with
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.Ql news.info
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and store them in the file
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.Pa /var/log/info .
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.Bd -literal -offset indent
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# Log all mail.info and news.info messages to info
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#
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mail,news.=info /var/log/info
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.Ed
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.Ss Advanced Filtering, part 1
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This logs all messages that come with either the
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.Ql info
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or the
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.Ql notice
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priority into the file
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.Pa /var/log/messages ,
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except for all messages that use the
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.Ql mail
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facility.
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.Bd -literal -offset indent
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# Log info and notice messages to messages file
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#
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*.=info;*.=notice;\\
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mail.none /var/log/messages
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.Ed
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.Ss Advanced Filtering, part 2
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This statement logs all messages that come with the
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.Ql info
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priority to the file
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.Pa /var/log/messages .
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But any message with either
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.Ql mail
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or the
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.Ql news
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facility are not logged.
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.Bd -literal -offset indent
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# Log info messages to messages file
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#
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*.=info;\\
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mail,news.none /var/log/messages
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.Ed
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.Ss Wall Messages
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This rule tells
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.Nm syslogd
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to write all emergency messages to all currently logged in users. This
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is the wall action.
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.Bd -literal -offset indent
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# Emergency messages will be displayed using wall
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#
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*.=emerg *
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.Ed
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.Ss Alerting Users
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This rule directs all messages of priority
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.Ql alert
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or higher to the terminals of the operator, i.e. of the users 'root'
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and 'joey', if they're logged in.
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.Bd -literal -offset indent
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# Messages of the priority alert will be directed
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# to the operator
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#
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*.alert root,joey
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.Ed
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.Ss Log Rotation
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This example logs all messages except kernel messages to the file
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.Pa /var/log/messages
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without syncing ('-') the file after each log message. When the file
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reaches 100 kiB it is rotated. In total are only 10 rotated files,
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including the main file itself and compressed files kept. The size
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argument takes the same modifiers as the
|
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.Xr syslogd 8
|
|
command line option,
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.Fl R .
|
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.Bd -literal -offset indent
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# Log all messages, including kernel, to messages file rotated
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# every 100 kB and keep up to 10 aged out and compressed files
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#
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*.*;kern.none -/var/log/messages ;rotate=100k:10
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.Ed
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.Ss Logging to Remote Syslog Server
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This rule redirects all messages to one remote host called
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.Ql finlandia ,
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with RFC5424 style formatting, and another remote host called
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.Ql sibelius ,
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but on a non-standard port and with RFC3164 formatting (i.e.,
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including timestamp and hostname).
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.Bd -literal -offset indent
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*.* @finlandia ;RFC5424
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*.* @sibelius:5514 ;RFC3164
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.Ed
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.Sh FILES
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.Bl -tag -compact -width /etc/syslog.d/*.conf
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.It /etc/syslog.conf
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Main configuration file for
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.Xr syslogd 8
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.It /etc/syslog.d/*.conf
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Recommended directory for .conf snippets (per subsystem)
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.El
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.Sh BUGS
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The effects of multiple selectors are sometimes not intuitive. For
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example
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.Ql mail.crit,*.err
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will select
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.Ql mail
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facility messages at the level of
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.Ql err
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or higher, not at the level of
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.Ql crit or higher.
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.Pp
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Also, if you specify a selector with an exclamation mark in it, which
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isn't preceded by a corresponding selector without an exclamation mark,
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nothing will be logged. Intuitively, the selector
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.Ql ftp.!alert
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on its own will select all
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.Ql ftp
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messages with priorities less than
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.Ql alert .
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In fact it selects nothing. Similarly,
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.Ql ftp.!=alert
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might reasonably be expected to select all
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.Ql ftp
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messages other than those with priority
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.Ql alert ,
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but again it selects nothing. It seems the selectors with exclamation
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marks in them should only be used as "filters" following selectors
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without exclamation marks.
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.Pp
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Finally, using a backslash to divide a line into two doesn't work if the
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backslash is used immediately after the end of the selector, without
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intermediate whitespace.
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.Sh SEE ALSO
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.Xr mkfifo 1 ,
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.Xr sysklogd 8 ,
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.Xr klogd 8 ,
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.Xr logger 1 ,
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.Xr syslog 2 ,
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.Xr syslogp 3 .
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.Sh AUTHORS
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The system log daemon
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.Nm syslogd
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is originally taken from BSD sources and later updated with new
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funcitonality from
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.Fx
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and
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.Nx .
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.An -nosplit
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.An Greg Wettstein Aq Mt greg@wind.enjellic.com
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performed the initial port to Linux.
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.An Martin Schulze Aq Mt joey@infodrom.org
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fixed some bugs, added several new features and took over maintenance.
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.An Joachim Nilsson Aq Mt troglobit@gmail.com
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later picked up the aging
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.Nm sysklogd
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|
and gave it a home at GitHub with new features imported from
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.Fx
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and
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.Nx .
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