xref: /freebsd/usr.sbin/syslogd/syslogd.8 (revision 42c159fe388a3765f69860c84183700af37aca8a)
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32.\"     @(#)syslogd.8	8.1 (Berkeley) 6/6/93
33.\" $FreeBSD$
34.\"
35.Dd November 24, 2001
36.Dt SYSLOGD 8
37.Os
38.Sh NAME
39.Nm syslogd
40.Nd log systems messages
41.Sh SYNOPSIS
42.Nm
43.Op Fl 46Adknosuv
44.Op Fl a Ar allowed_peer
45.Op Fl b Ar bind_address
46.Op Fl f Ar config_file
47.Op Fl m Ar mark_interval
48.Op Fl p Ar log_socket
49.Op Fl P Ar pid_file
50.Op Fl l Ar path
51.Sh DESCRIPTION
52The
53.Nm
54daemon reads and logs messages to the system console, log files, other
55machines and/or users as specified by its configuration file.
56.Pp
57The options are as follows:
58.Bl -tag -width indent
59.It Fl 4
60Forces
61.Nm
62to use IPv4 addresses only.
63.It Fl 6
64Forces
65.Nm
66to use IPv6 addresses only.
67.It Fl A
68Ordinarily,
69.Nm
70tries to send the message to only one address
71even if the host has more than one A or AAAA record.
72If this option is specified,
73.Nm
74tries to send the message to all addresses.
75.It Fl a Ar allowed_peer
76Allow
77.Ar allowed_peer
78to log to this
79.Nm
80using UDP datagrams.  Multiple
81.Fl a
82options may be specified.
83.Pp
84.Ar Allowed_peer
85can be any of the following:
86.Bl -tag -width "ipaddr/masklen[:service]XX"
87.It Xo
88.Sm off
89.Ar ipaddr
90.No / Ar masklen
91.Op : Ar service
92.Sm on
93.Xc
94Accept datagrams from
95.Ar ipaddr
96(in the usual dotted quad notation) with
97.Ar masklen
98bits being taken into account when doing the address comparison.
99.Ar ipaddr
100can be also IPv6 address by enclosing the address with
101.Ql \&[
102and
103.Ql \&] .
104If specified,
105.Ar service
106is the name or number of an UDP service (see
107.Xr services 5 )
108the source packet must belong to.  A
109.Ar service
110of
111.Ql \&*
112allows packets being sent from any UDP port.  The default
113.Ar service
114is
115.Ql syslog .
116If
117.Ar ipaddr
118is IPv4 address, a missing
119.Ar masklen
120will be substituted by the historic class A or class B netmasks if
121.Ar ipaddr
122belongs into the address range of class A or B, respectively, or
123by 24 otherwise.  If
124.Ar ipaddr
125is IPv6 address, a missing
126.Ar masklen
127will be substituted by 128.
128.It Xo
129.Sm off
130.Ar domainname Op : Ar service
131.Sm on
132.Xc
133Accept datagrams where the reverse address lookup yields
134.Ar domainname
135for the sender address.  The meaning of
136.Ar service
137is as explained above.
138.It Xo
139.Sm off
140.No * Ar domainname Op : Ar service
141.Sm on
142.Xc
143Same as before, except that any source host whose name
144.Em ends
145in
146.Ar domainname
147will get permission.
148.El
149.Pp
150The
151.Fl a
152options are ignored if the
153.Fl s
154option is also specified.
155.It Fl b Ar bind_address
156Specify one specific IP address or hostname to bind to.
157If a hostname is specified,
158the IPv4 or IPv6 address which corresponds to it is used.
159.It Fl c
160Disable the compression of repeated instances of the same line
161into a single line of the form
162.Dq Li "last message repeated N times"
163when the output is a pipe to another program.
164If specified twice, disable this compression in all cases.
165.It Fl d
166Put
167.Nm
168into debugging mode.  This is probably only of use to developers working on
169.Nm .
170.It Fl f
171Specify the pathname of an alternate configuration file;
172the default is
173.Pa /etc/syslog.conf .
174.It Fl k
175Disable the translation of
176messages received with facility
177.Dq kern
178to facility
179.Dq user .
180Usually the
181.Dq kern
182facility is reserved for messages read directly from
183.Pa /dev/klog .
184.It Fl m
185Select the number of minutes between
186.Dq mark
187messages; the default is 20 minutes.
188.It Fl n
189Disable dns query for every request.
190.It Fl o
191Prefix kernel messages with the full kernel boot file as determined by
192.Xr getbootfile 3 .
193Without this, the kernel message prefix is always
194.Dq Li kernel: .
195.It Fl p
196Specify the pathname of an alternate log socket to be used instead;
197the default is
198.Pa /var/run/log .
199.It Fl P
200Specify an alternative file in which to store the process ID.
201The default is
202.Pa /var/run/syslog.pid .
203.It Fl l
204Specify a location where
205.Nm
206should place an additional log socket.
207Up to 19 additional logging sockets can be specified.
208The primary use for this is to place additional log sockets in
209.Pa /var/run/log
210of various chroot filespaces.
211.It Fl s
212Operate in secure mode.  Do not log messages from remote machines.  If
213specified twice, no network socket will be opened at all, which also
214disables logging to remote machines.
215.It Fl u
216Unique priority logging.  Only log messages at the specified priority.
217Without this option, messages at the stated priority or higher are logged.
218This option changes the default comparison from
219.Dq =>
220to
221.Dq = .
222.It Fl v
223Verbose logging.  If specified once, the numeric facility and priority are
224logged with each locally-written message.  If specified more than once,
225the names of the facility and priority are logged with each locally-written
226message.
227.El
228.Pp
229The
230.Nm
231daemon reads its configuration file when it starts up and whenever it
232receives a hangup signal.
233For information on the format of the configuration file,
234see
235.Xr syslog.conf 5 .
236.Pp
237The
238.Nm
239daemon reads messages from the
240.Tn UNIX
241domain socket
242.Pa /var/run/log ,
243from an Internet domain socket specified in
244.Pa /etc/services ,
245and from the special device
246.Pa /dev/klog
247(to read kernel messages).
248.Pp
249The
250.Nm
251daemon creates its process ID file,
252by default
253.Pa /var/run/syslog.pid ,
254and stores its process
255ID there.
256This can be used to kill or reconfigure
257.Nm .
258.Pp
259The message sent to
260.Nm
261should consist of a single line.
262The message can contain a priority code, which should be a preceding
263decimal number in angle braces, for example,
264.Sq Aq 5 .
265This priority code should map into the priorities defined in the
266include file
267.Aq Pa sys/syslog.h .
268.Pp
269For security reasons,
270.Nm
271will not append to log files that do not exist;
272therefore, they must be created manually before running
273.Nm .
274.Sh FILES
275.Bl -tag -width /var/run/syslog.pid -compact
276.It Pa /etc/syslog.conf
277configuration file
278.It Pa /var/run/syslog.pid
279default process ID file
280.It Pa /var/run/log
281name of the
282.Tn UNIX
283domain datagram log socket
284.It Pa /dev/klog
285kernel log device
286.El
287.Sh SEE ALSO
288.Xr logger 1 ,
289.Xr syslog 3 ,
290.Xr services 5 ,
291.Xr syslog.conf 5
292.Sh HISTORY
293The
294.Nm
295command appeared in
296.Bx 4.3 .
297.Pp
298The
299.Fl a ,
300.Fl s ,
301.Fl u ,
302and
303.Fl v
304options are
305.Fx 2.2
306extensions.
307.Sh BUGS
308The ability to log messages received in UDP packets is equivalent to
309an unauthenticated remote disk-filling service, and should probably be
310disabled by default.  Some sort of
311.No inter- Ns Nm syslogd
312authentication mechanism ought to be worked out.  To prevent the worst
313abuse, use of the
314.Fl a
315option is therefore highly recommended.
316.Pp
317The
318.Fl a
319matching algorithm doesn't pretend to be very efficient; use of numeric
320IP addresses is faster than domain name comparison.  Since the allowed
321peer list is being walked linearly, peer groups where frequent messages
322are being anticipated from should be put early into the
323.Fl a
324list.
325.Pp
326The log socket was moved from
327.Pa /dev
328to ease the use of a read-only root filesystem.
329This may confuse
330some old binaries so that a symbolic link might be used for a
331transitional period.
332