path: root/usr.sbin/syslogd/syslogd.8

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.\"     from: @(#)syslogd.8	8.1 (Berkeley) 6/6/93
.\"	$NetBSD: syslogd.8,v 1.3 1996/01/02 17:41:48 perry Exp $
.\"
.Dd $Mdocdate: September 23 2016 $
.Dt SYSLOGD 8
.Os
.Sh NAME
.Nm syslogd
.Nd log system messages
.Sh SYNOPSIS
.Nm syslogd
.Bk -words
.Op Fl 46dFhnuV
.Op Fl a Ar path
.Op Fl C Ar CAfile
.Op Fl c Ar cert_file
.Op Fl f Ar config_file
.Op Fl K Ar CAfile
.Op Fl k Ar key_file
.Op Fl m Ar mark_interval
.Op Fl p Ar log_socket
.Op Fl S Ar listen_address
.Op Fl s Ar reporting_socket
.Op Fl T Ar listen_address
.Op Fl U Ar bind_address
.Ek
.Sh DESCRIPTION
.Nm
reads and logs messages to the system console, log files, pipes to
other programs, other machines and/or users as specified by its
configuration file.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl 4
Forces
.Nm
to use only IPv4 addresses for UDP.
.It Fl 6
Forces
.Nm
to use only IPv6 addresses for UDP.
.It Fl a Ar path
Specify a location where
.Nm
should place an additional log socket.
Up to 20 additional logging sockets can be specified.
The primary use for this is to place additional log sockets in
.Pa /dev/log
of various chroot filespaces, though the need for these is
less urgent after the introduction of
.Xr sendsyslog 2 .
.It Fl C Ar CAfile
PEM encoded file containing CA certificates used for certificate
validation of a remote loghost;
the default is
.Pa /etc/ssl/cert.pem .
.It Fl c Ar cert_file
PEM encoded file containing the client certificate for TLS connections
to a remote host.
The default is not to use a client certificate for the connection
to a syslog server.
This option has to be used together with
.Fl k Ar key_file .
.It Fl d
Enable debugging to the standard output,
and do not disassociate from the controlling terminal.
.It Fl F
Run in the foreground instead of disassociating from the controlling
terminal and running as a background daemon.
.It Fl f Ar config_file
Specify the pathname of an alternate configuration file;
the default is
.Pa /etc/syslog.conf .
.It Fl h
Include the hostname when forwarding messages to a remote host.
.It Fl K Ar CAfile
PEM encoded file containing CA certificates used for client certificate
validation on the local server socket.
By default incoming connections from any TLS server are allowed.
.It Fl k Ar key_file
PEM encoded file containing the client private key for TLS connections
to a remote host.
This option has to be used together with
.Fl c Ar cert_file .
.It Fl m Ar mark_interval
Select the number of minutes between
.Dq mark
messages; the default is 20 minutes.
.It Fl n
Print source addresses numerically rather than symbolically.
This saves an address-to-name lookup for each incoming message,
which can be useful when combined with the
.Fl u
option on a loghost with no DNS cache.
Messages from the local host will still be logged with
the symbolic local host name.
.It Fl p Ar log_socket
Specify the pathname of an alternate log socket to be used instead;
the default is
.Pa /dev/log .
.It Fl S Ar listen_address
Create a TLS listen socket for receiving encrypted messages and
bind it to the specified address.
A port number may be specified using the
.Ar host : Ns Ar port
syntax.
The parameter is also used to find a suitable server key and
certificate in
.Pa /etc/ssl/ .
.It Fl s Ar reporting_socket
Specify path to an
.Dv AF_LOCAL
socket for use in reporting logs stored in memory buffers using
.Xr syslogc 8 .
.It Fl T Ar listen_address
Create a TCP listen socket for receiving messages and bind it to
the specified address.
There is no well-known port for syslog over TCP, so a port number
must be specified using the
.Ar host : Ns Ar port
syntax.
.It Fl U Ar bind_address
Create a UDP socket for receiving messages and bind it to the
specified address.
This can be used, for example, with a pf divert-to rule to receive
packets when syslogd is bound to localhost.
A port number may be specified using the
.Ar host : Ns Ar port
syntax.
.It Fl u
Select the historical
.Dq insecure
mode, in which syslogd will
accept input from the UDP port.
Some software wants this, but you can be subjected to a variety of
attacks over the network, including attackers remotely filling logs.
.It Fl V
Do not perform remote server certificate and hostname validation
when sending messages.
.El
.Pp
.Nm
reads its configuration file,
.Xr syslog.conf 5 ,
when it starts up and whenever it
receives a hangup signal.
It creates the file
.Pa /var/run/syslog.pid
and stores its process ID there.
The PID can be used to kill or reconfigure
.Nm .
.Pp
.Nm
opens a UDP socket, as specified
in
.Pa /etc/services ,
for sending forwarded messages.
By default all incoming data on this socket is discarded.
If insecure mode is switched on with
.Fl u ,
it will also read messages from the socket.
.Nm
also opens and reads messages from the
.Ux Ns -domain
socket
.Pa /dev/log ,
and from the special device
.Pa /dev/klog
(to read kernel messages),
and from
.Xr sendsyslog 2
(to read messages from userland processes).
.Pp
The message sent to
.Nm
should consist of a single line.
The message can contain a priority code, which should be a preceding
decimal number in angle braces, for example,
.Dq <5> .
This priority code should map into the priorities defined in the
include file
.In sys/syslog.h .
.Pp
When sending syslog messages to a remote loghost via TLS, the
server's certificate and hostname are validated to prevent malicious
servers from reading messages.
If the server has a certificate with a matching hostname signed by
a CA in
.Pa /etc/ssl/cert.pem ,
it is verified with that by default.
If the server has a certificate with a matching hostname signed by
a private CA, use the
.Fl C
option and put that CA into
.Ar CAfile .
Validation can be explicitly turned off using the
.Fl V
option.
If the server is accepting messages only from clients with a trusted
client certificate, use the
.Fl k
and
.Fl c
options to authenticate
.Nm
with this certificate.
.Pp
When receiving syslog messages from a TLS client, there must be
a server key and certificate in
.Pa /etc/ssl/private/host Ns Oo : Ns Ar port Oc Ns Ar .key
and
.Pa /etc/ssl/host Ns Oo : Ns Ar port Oc Ns Ar .crt .
If the client uses certificates to authenticate, the CA of the
client's certificate may be added to
.Ar CAfile
using the
.Fl K
option to protect from messages being spoofed by malicious clients.
.Sh FILES
.Bl -tag -width /var/run/syslog.pid -compact
.It Pa /etc/syslog.conf
Configuration file.
.It Pa /var/run/syslog.pid
Process ID of current
.Nm .
.It Pa /dev/log
Name of the
.Ux Ns -domain
datagram log socket.
.It Pa /dev/klog
Kernel log device.
.It Pa /etc/ssl/
Private keys and public certificates.
.El
.Sh SEE ALSO
.Xr logger 1 ,
.Xr syslog 3 ,
.Xr services 5 ,
.Xr syslog.conf 5 ,
.Xr newsyslog 8 ,
.Xr syslogc 8
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.3 .
.Sh CAVEATS
.Nm
does not create files,
it only logs to existing ones.