577 lines
15 KiB
Groff
577 lines
15 KiB
Groff
.\" -*- nroff -*-
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.\" Copyright (c) 1983, 1986, 1991, 1993
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.\" The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)syslogd.8 8.1 (Berkeley) 6/6/93
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.\" $FreeBSD$
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.\"
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.Dd May 5, 2021
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.Dt SYSLOGD 8
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.Os sysklogd
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.Sh NAME
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.Nm syslogd
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.Nd log systems messages
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.Sh SYNOPSIS
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.Nm
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.Op Fl ?46AdFHKknsTv
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.Op Fl a Ar addr[/len][:port]
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.Op Fl a Ar name[:port]
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.Op Fl b Ar addr[:port]
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.Op Fl b Ar :port
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.Op Fl C Ar file
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.Op Fl f Ar file
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.Op Fl m Ar interval
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.Op Fl P Ar file
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.Op Fl p Ar sock
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.Op Fl r Ar size[:count]
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.Sh DESCRIPTION
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The
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.Nm
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utility reads and logs messages to the system console, log files, other
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machines and/or users as specified by its configuration file.
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.Pp
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.Nm
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support RFC3164 and RFC5424 style log messages for both local and remote
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logging using Internet and UNIX domain sockets. Differences in style is
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shown below.
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.Pp
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.Bl -tag -compact -width "RFC3164:"
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.It Sy RFC3164:
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.Li Aug 24 05:14:15 192.0.2.1 myproc[8710]: Kilroy was here.
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.It Sy RFC5424:
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.Li 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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Note, for remote logging the messages are prefixed with
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.Ql <PRI>
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or
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.Ql <PRI>1 ,
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respectively.
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.Pp
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.Nm
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is derived from BSD sources, today
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.Fx
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is the reference for
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.Nm
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and
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.Nx
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for the new
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.Xr syslogp 3
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API, which fully supports the new features of RFC5424. Please note; 1)
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the intention is to follow standard BSD
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.Nm
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behavior, 2) despite having a stand-alone
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.Xr syslog 3 ,
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and
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.Xr syslogp 3
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API in libsyslog,
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.Nm
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interacts transparently with the standard C library
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.Xr syslog 3
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API, as implemented in GLIBC, musl libc, and uClibc.
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.Pp
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When
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.Nm
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starts up it reads its main configuration file
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.Pa /etc/syslog.conf ,
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or an alternate file given with the
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.Fl f Ar file
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option. For details on how to configure syslog priority
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(facility.severity) filtering, see
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.Xr syslog.conf 5 .
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.Sh OPTIONS
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By default,
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.Nm
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reads messages from the
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.Ux
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domain socket
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.Pa /dev/log ,
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from an Internet domain socket specified in
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.Pa /etc/services ,
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and from
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.Pa /dev/kmsg
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.Pq to read kernel messages .
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The command line options defined below can be used to change this
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behavior.
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.Pp
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The options are as follows:
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.Bl -tag -width indent
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.It Fl 4
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Force
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.Nm
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to use IPv4 addresses only.
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.It Fl 6
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Force
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.Nm
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to use IPv6 addresses only.
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.It Fl A
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Ordinarily,
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.Nm
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tries to send the message to only one address
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even if the host has more than one A or AAAA record.
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If this option is specified,
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.Nm
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tries to send the message to all addresses.
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.It Fl a Ar address[/len][:service] | Fl a Ar domainname[:service]
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Allow peers to log to this syslogd using UDP datagrams. Multiple
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.Fl a
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options may be specified. Any
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.Fl a
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option is ignored if the
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.Fl s
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option is also specified.
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.Pp
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The peer argument may be any of the following:
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.Bl -tag -width 'address[/len][:service]'
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.It Ql address[/len][:service]
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Accept datagrams from IP
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.Ar address ,
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which can be specified as an IPv4 address or as an IPv6 address enclosed
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with
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.Sq \&[
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and
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.Sq \&] .
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If specified, service is the name or port number of an UDP service (see
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.Xr services 5 )
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the source packet must belong to. A service of
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.Ql *
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accepts UDP packets from any source port. The default service is
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.Ql syslog .
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If
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.Ar address
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is an IPv4 address, a missing prefix
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.Ar len
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will be substituted by the historic class A or class B netmasks if
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.Ar address
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belongs in the address range of class A or B, respectively, or by'
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.Ar /24
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otherwise. If
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.Ar address
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is an IPv6 address, a missing prefix
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.Ar len
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will be substituted by 128.
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.It Ql domainname[:service]
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Accept datagrams where the reverse address lookup yields
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.Ar domainname
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for the sender address. The meaning of
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.Ar service
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is as explained above.
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.Ar domainname
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can contain special characters of a shell-style pattern such as
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.Ql * .
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.El
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.It Xo
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.Fl b
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.Sm off
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.Ar address Op \&: Ar service
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.Sm on
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.Xc
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.It Xo
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.Fl b
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.Sm off
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.Li \&: Ar service
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.Sm on
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.Xc
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Bind to a specific address and/or port.
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The address can be specified as a hostname,
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and the port as a service name.
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If an IPv6 address is specified, it should be enclosed with
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.Ql \&[
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and
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.Ql \&] .
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The default
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.Ar service
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is
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.Ql syslog .
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This option can be specified multiple times to bind to
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multiple addresses and/or ports.
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.It Fl C Ar file
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File to use for caching last read kernel sequence number from
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.Pa /dev/kmsg ,
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default:
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.Pa /run/syslogd.cache .
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If
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.Nm
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cannot write to, or read from, this file it will cause repeated kernel
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log messages when restarting
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.Nm .
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.Pp
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.Sy Note:
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.Nm
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relies on this file being removed at system reboot. The default
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location depends on the system and how
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.Nm
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was configured.
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.It Fl d
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Put
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.Nm
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into debugging mode.
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This is probably only of use to developers working on
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.Nm .
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See the
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.Sx DEBUGGING
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section for more information.
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.It Fl f Ar file
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Specify the path name of an alternate configuration file;
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the default is
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.Pa /etc/syslog.conf .
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.It Fl F
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Run
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.Nm
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in the foreground,
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rather than going into daemon mode.
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This is useful if some other process uses
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.Xr fork 2
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and
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.Xr exec 3
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to run
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.Nm ,
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and wants to monitor when and how it exits.
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.It Fl H
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When logging remote messages use hostname from the message (if supplied)
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instead of using address from which the message was received.
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.It Fl K
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Keep (trust) kernel timestamp.
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.Pp
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On Linux systems the
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.Pa /dev/kmsg
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timestamp is a monotonic clock, in microseconds, relative to the boot of
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the system. This timestamp is, among other things,
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.Sy not
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adjusted for suspend/resume cycles, meaning the kernel logs can start to
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go out of sync with the rest of the system. This in turn can make it
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really hard to correlate events.
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.Pp
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.Nm
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by default only trusts the kernel timestamp when starting up the first
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time. As soon as the the kernel ring buffer has been emptied,
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.Nm
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uses its own current time for each received kernel log message. This
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option disables that behavior.
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.It Fl k
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Disable the translation of
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messages received with facility
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.Dq kern
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to facility
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.Dq user .
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Usually the
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.Dq kern
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facility is reserved for messages read directly from
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.Pa /dev/kmsg .
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.It Fl m Ar interval
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Select the number of minutes between
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.Dq mark
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messages; the default is 20 minutes. Setting this to zero disables log
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marks.
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.It Fl n
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Disable DNS query for every request.
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.It Fl p Ar socket
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Specify the path name of an alternate log socket to be used instead;
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the default is
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.Pa /dev/log .
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When a single
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.Fl p
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option is specified, the default path name is replaced with the
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specified one. When two or more
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.Fl p
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options are specified, the remaining path names are treated as
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additional log sockets.
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.It Fl P Ar file
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Specify an alternative file in which to store the process ID.
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The default is
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.Pa /var/run/syslogd.pid .
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.It Fl r Ar size[:count]
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Enable built-in support for log rotation of files listed in
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.Pa /etc/syslog.conf .
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This feature is particularly useful for small and embedded systems that
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do not want the overhead of
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.Xr cron 8
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and
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.Xr logrotate 8 .
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.Pp
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The option controls the max size and number of backup files kept by the
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built-in log-rotation. When present on the command line it activates
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log rotation of all files with the given maximum size. It is also
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possible to control log rotate per log file, see
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.Xr syslog.conf 5
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for details.
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.Pp
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The size argument takes optional modifiers; k, M, G. E.g., 100M is
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100 MiB, 42k is 42 kiB, etc.
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.Pp
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The optional number of files kept include both gzipped files and the
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first rotated (not zipped) file. The default for this, when omitted,
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is 5.
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.It Fl s
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Operate in secure mode. Do not log messages from remote machines. If
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specified twice, no network socket will be opened at all, which also
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disables logging to remote machines.
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.It Fl T
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Always use the local time and date for messages received from the network,
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instead of the timestamp field supplied in the message by the remote host.
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This is useful if some of the originating hosts cannot keep time properly
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or are unable to generate a correct timestamp.
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.It Fl v
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Show program version and exit.
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.El
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.Pp
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The
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.Nm
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utility reads its configuration file when it starts up and whenever it
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receives a hangup signal.
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For information on the format of the configuration file,
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see
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.Xr syslog.conf 5 .
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.Pp
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The
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.Nm
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utility creates its process ID file,
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by default
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.Pa /var/run/syslogd.pid ,
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and stores its process ID there. This can be used to kill or
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reconfigure
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.Nm .
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.Pp
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The message sent to
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.Nm
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should consist of a single line. The message can contain a priority
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code, which should be a preceding decimal number in angle braces, for
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example,
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.Sq Aq 5 .
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This priority code should map into the priorities defined in the
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include file
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.In sys/syslog.h .
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To log with RFC5424 style messages the priority code must be directly
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followed by the version number, this is all handled by libsyslog, which
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is the
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.Nx
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.Xr syslogp 3
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API included with the
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.Nm sysklogd
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project.
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.Pp
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The date and time are taken from the received message. If the format of
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the timestamp field is incorrect, time obtained from the local host is
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used instead. This can be overridden by the
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.Fl T
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flag.
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.Sh SECURITY
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There are a number of methods of protecting a machine:
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.Bl -enum
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.It
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Disabling inet domain sockets will limit risk to the local machine. Use
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the secure mode flag
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.Fl s
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for this.
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.It
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When secure mode cannot be used, only allow certain remote peers using
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the
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.Fl a Ar PEER
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flag.
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.It
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Implement kernel firewalling to limit which hosts or networks have
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access to the 514/UDP socket.
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.It
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Logging can be directed to an isolated or non-root filesystem which,
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if filled, will not impair the machine.
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.It
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Most modern UNIX filesystems can be configured to limit a certain
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percentage of a filesystem to usage by root only.
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.El
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.Sh DEBUGGING
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When debug mode
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.Fl ( d )
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is enabled
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.Nm
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only the first
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.Fn init
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is shown.
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.Nm
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then prompts you to send
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.Ar SIGUSR1
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to continue debugging. The output is very verbose and is probably only
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useful to developers.
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.Pp
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When
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.Nm
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receives
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.Ar SIGHUP
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it reloads its configuration file, and at the end of the
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.Fn init
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sequence all log targets are listed with their respective priority per
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facility, the action and the log format used:
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.Pp
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.Bl -tag -width priority
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.It priority
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Bit mapped priorities listed per facility, one priority per facility,
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starting with kernel as the left-most column.
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.It action
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FILE, remote sink (FORW), WALL, etc. See
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.Xr syslog.conf 5
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for details.
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.It args
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The action argument and the log format used. E.g., for FILE actions the
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log filename, for FORW action the remote host:port. The format is one
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of; BSD, RFC5424, or RFC3164. The latter is the default except for FORW
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actions.
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.El
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.Sh SIGNALS
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.Nm
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supports the following signals:
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.Pp
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.Bl -tag -width "TERM, QUIT"
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.It HUP
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This lets
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.Nm
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perform a re-initialization. All open files are closed, the
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configuration file (see above) is reread and the
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.Xr syslog 3
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facility is started again.
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.It TERM
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This tells
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.Nm
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to exit gracefully. Flushing any log files to disk.
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.It INT, QUIT
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In debug mode these are ignored. In normal operation they act as
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SIGTERM.
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.It USR1
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In debug mode this switches debugging on/off. In normal operation
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it is ignored.
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.El
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.Pp
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|
For convenience the PID is by default stored in
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.Pa /var/run/syslogd.pid .
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A script can look for the existence of this file to determine if
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.Nm
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is running, and then send signals:
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.Bd -literal -offset indent
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kill -SIGNAL `cat /var/run/syslogd.pid`
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.Ed
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.Sh FILES
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.Bl -tag -width /etc/syslog.d/50-default.conf -compact
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.It Pa /etc/syslog.conf
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configuration file. See
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.Xr syslog.conf 5
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for more information.
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.It Pa /etc/syslog.d/*.conf
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conventional sub-directory of
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.Pa .conf
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files read by
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.Nm .
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.It Pa /etc/syslog.d/50-default.conf
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conventional name for default rules.
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.It Pa /var/run/syslogd.pid
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default process ID file
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.It Pa /var/run/syslogd.cache
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cache of last read sequence number from
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.Pa /dev/kmsg .
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Please note,
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.Nm
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relies on this file being removed at system reboot.
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.It Pa /dev/log
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name of the
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.Ux
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domain datagram log socket
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.It Pa /dev/kmsg
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kernel log device
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.El
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.Sh SEE ALSO
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.Xr logger 1 ,
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.Xr syslog 3 ,
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.Xr syslogp 3 ,
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.Xr services 5 ,
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.Xr syslog.conf 5 ,
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.Sh HISTORY
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|
.Nm
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|
was originally ported to Linux by
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.An Greg Wettstein Aq Mt greg@wind.enjellic.com
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and the project was named
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.Nm sysklogd
|
|
when a separate log daemon,
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.Nm klogd ,
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for Linux kernel messages was added.
|
|
.Pp
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|
It was the default
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.Nm
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|
in Debian and Ubuntu, maintained by
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.An Martin Schulze Aq Mt joey@infodrom.org ,
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|
who fixed some bugs and added several new features. When Debian replaced
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.Nm sysklogd
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with
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.Nm rsyslogd
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the project was abandoned.
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.Pp
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|
In 2018
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.An Joachim Wiberg Aq Mt troglobit@gmail.com
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picked up maintenance. In 2019 the project was revived with fresh DNA
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strands from both
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.Fx
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and
|
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.Nx ,
|
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.Nm klogd
|
|
was removed in v2.1 and the project was then re-licensed under the
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3-clause BSD license, like its brethren.
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.Pp
|
|
The
|
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.Nm
|
|
utility first appeared in
|
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.Bx 4.3 .
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.Sh BUGS
|
|
The ability to log messages received in UDP packets is equivalent to an
|
|
unauthenticated remote disk-filling service, and should probably be
|
|
disabled
|
|
.Fl ( s )
|
|
by default. (The shipped systemd unit file disables this by default.)
|
|
See also
|
|
.Sx SECURITY
|
|
for more information on this. A future version of
|
|
.Nm
|
|
may include support for TLS, RFC5425, which includes authentication of
|
|
both senders and receivers. For now there is the
|
|
.Fl a
|
|
option, which is strongly recommended when operating as a remote sink.
|
|
.Pp
|
|
The
|
|
.Fl a
|
|
matching algorithm does not pretend to be very efficient;
|
|
use of numeric IP addresses is faster than domain name comparison.
|
|
Since the allowed peer list is being walked linearly,
|
|
peer groups where frequent messages are being anticipated
|
|
from should be put early into the
|
|
.Fl a
|
|
list.
|
|
.Pp
|
|
As mentioned in the
|
|
.Sx DESCRIPTION ,
|
|
.Nm
|
|
transparently supports the standard C library
|
|
.Xr syslog 3
|
|
API. If a binary linked to the standard C libraries does not operate
|
|
correctly, this should be reported as a bug to the
|
|
.Lk https://github.com/troglobit/sysklogd/issues sysklogd issue tracker
|