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.\"     from: @(#)syslog.conf.5	8.1 (Berkeley) 6/9/93
.\"     $OpenBSD: syslog.conf.5,v 1.36 2018/02/02 10:53:44 jmc Exp $
.\"	$NetBSD: syslog.conf.5,v 1.4 1996/01/02 17:41:46 perry Exp $
.\"
.Dd $Mdocdate: February 2 2018 $
.Dt SYSLOG.CONF 5
.Os
.Sh NAME
.Nm syslog.conf
.Nd syslogd(8) configuration file
.Sh DESCRIPTION
The
.Nm syslog.conf
file is the configuration file for the
.Xr syslogd 8
program.
It consists of blocks of lines separated by
.Em program
specifications, with each line containing two fields: the
.Em selector
field which specifies the types of messages and priorities to which the
line applies, and an
.Em action
field which specifies the action to be taken if a message
.Xr syslogd 8
receives matches the selection criteria.
The
.Em selector
field is separated from the
.Em action
field by one or more tab or space characters.
.Pp
The
.Em selectors
are encoded as a
.Em facility ,
a period
.Pq Ql \&. ,
and a
.Em level ,
with no intervening whitespace.
Both the
.Em facility
and the
.Em level
are case insensitive.
.Pp
The
.Em facility
describes the part of the system generating the message, and is one of
the following keywords: auth, authpriv, cron, daemon, ftp, kern, lpr, mail,
mark, news, syslog, user, uucp and local0 through local7.
These keywords (with the exception of mark) correspond to the
similar
.Dq Dv LOG_
values specified to the
.Xr openlog 3
and
.Xr syslog 3
library routines.
.Pp
The
.Em level
describes the severity of the message, and is a keyword from the
following ordered list (highest to lowest): emerg, alert, crit, err,
warning, notice, info and debug.
These keywords correspond to the
similar
.Pq Dv LOG_
values specified to the
.Xr syslog 3
library routine.
.Pp
Each block of lines is separated from the previous block by a tag.
The tag is a line beginning with
.Em !prog
and each block will be associated with calls to syslog from that specific
program.
When a message matches multiple blocks, the action of each matching
block is taken.
If no tag is specified at the beginning of the file,
every line is checked for a match and acted upon
.Pq at least until a tag is found .
.Pp
.Em !!prog
causes the subsequent block to abort evaluation when a message matches,
ensuring that only a single set of actions is taken.
.Em !*\&
can be used to ensure that any ensuing blocks are further evaluated
(i.e. cancelling the effect of a
.Em !prog
or
.Em !!prog ) .
.Pp
Blocks starting with
.Em +host
or
.Em ++host
or
.Em +*
work the same way as their
.Em prog
counterparts, but they match on the hostname instead of the program
name.
.Pp
See
.Xr syslog 3
for further descriptions of both the
.Em facility
and
.Em level
keywords and their significance.
It's recommended that selections be made on
.Em facility
rather than
.Em program ,
since the latter can easily vary in a networked environment.
In some cases, though, an appropriate
.Em facility
simply doesn't exist.
.Pp
If a received message matches the specified
.Em facility
and is of the specified
.Em level
.Pq Em or a higher level ,
and the first word in the message after the date matches the
.Em program ,
the action specified in the
.Em action
field will be taken.
.Pp
Multiple
.Em selectors
may be specified for a single
.Em action
by separating them with semicolon
.Pq Ql \&;
characters.
It is important to note, however, that each
.Em selector
can modify the ones preceding it.
.Pp
Multiple
.Em facilities
may be specified for a single
.Em level
by separating them with comma
.Pq Ql \&,
characters.
.Pp
An asterisk
.Pq Ql *
can be used to specify all
.Em facilities ,
all
.Em levels
or all
.Em programs .
.Pp
The special
.Em facility
.Dq mark
receives a message at priority
.Dq info
every 20 minutes (see
.Xr syslogd 8 ) .
This is not enabled by a
.Em facility
field containing an asterisk.
.Pp
The special
.Em level
.Dq none
disables a particular
.Em facility .
.Pp
The
.Em action
field of each line specifies the action to be taken when the
.Em selector
field selects a message.
There are six forms:
.Bl -bullet
.It
A pathname (beginning with a leading slash).
Selected messages are appended to the file.
.It
A pipe to another program (beginning with a leading pipe symbol).
The given program is started and presented the selected messages
on its standard input.
If the program exits,
.Xr syslogd 8
tries to restart it.
.It
A hostname (preceded by an at
.Pq Ql @
sign).
Selected messages are forwarded to the
.Xr syslogd 8
program on the named host.
A port number may be specified using the
.Ar host:port
syntax.
This is optional for UDP and TLS.
There is no well-known port for syslog over TCP, so in this case it
is mandatory to specify the port.
IPv6 addresses can be used by surrounding the address portion with
square brackets
.Po
.Ql [\&
and
.Ql ]\&
.Pc .
A prefix udp4:// or udp6:// in front of the hostname and after the
at sign will force IPv4 or IPv6 addresses for UDP transport.
The prefixes tcp[46]:// or tls[46]:// send messages over TCP or
TLS, respectively, with an optional IP version 4 or 6.
.It
A comma separated list of users.
Selected messages are written to those users
if they are logged in.
.It
An asterisk.
Selected messages are written to all logged-in users.
.It
A colon, followed by a memory buffer size
.Pq in kilobytes ,
followed by another colon, followed by a buffer name.
Selected messages are written to an in-memory buffer that may be read using
.Xr syslogc 8 .
Memory buffered logging is useful to provide access to log data on devices
that lack local storage (e.g. diskless workstations or routers).
The largest allowed buffer size is 256kb.
.El
.Pp
Blank lines and lines whose first non-blank character is a hash
.Pq Ql #
character are ignored.
.Sh FILES
.Bl -tag -width /etc/syslog.conf -compact
.It Pa /etc/syslog.conf
The
.Xr syslogd 8
configuration file.
.El
.Sh EXAMPLES
A configuration file might appear as follows:
.Bd -literal
# Log info (and higher) messages from spamd only to
# a dedicated file, discarding debug messages.
# Matching messages abort evaluation of further rules.
!!spamd
daemon.info						/var/log/spamd
daemon.debug						/dev/null
!*

# Log all kernel messages, authentication messages of
# level notice or higher and anything of level err or
# higher to the console.
# Don't log private authentication messages!
*.err;kern.*;auth.notice;authpriv.none			/dev/console

# Log anything (except mail) of level info or higher.
# Don't log private authentication messages!
*.info;mail.none;authpriv.none				/var/log/messages

# The authpriv file has restricted access.
authpriv.*						/var/log/secure

# Log all the mail messages in one place.
mail.*							/var/log/maillog

# Everybody gets emergency messages, plus log them on another
# machine.
*.emerg							*
*.emerg							@arpa.berkeley.edu

# Root and Eric get alert and higher messages.
*.alert							root,eric

# Log everything coming from host bastion to a separate file.
++bastion
*.*							/var/log/bastion
+*

# Save mail and news errors of level err and higher in a
# special file.
mail,news.err						/var/log/spoolerr

# Save ftpd transactions along with mail and news.
!ftpd
*.*							/var/log/spoolerr

# Keep a copy of all logging in a 32k memory buffer named "debug".
*.debug							:32:debug

# Store notices and authpriv messages in a 64k buffer named "important".
*.notice,authpriv.*					:64:important

# Feed everything to logsurfer.
*.*						|/usr/local/sbin/logsurfer
.Ed
.Sh SEE ALSO
.Xr syslog 3 ,
.Xr syslogc 8 ,
.Xr syslogd 8
.Sh HISTORY
The
.Nm
file appeared in
.Bx 4.3 ,
along with
.Xr syslogd 8 .
.Pp
Historic versions of
.Xr syslogd 8
did not support space-delimited fields.
.Sh BUGS
The effects of multiple selectors are sometimes not intuitive.
For example
.Dq mail.crit;*.err
will select
.Dq mail
facility messages at the level of
.Dq err
or higher, not at the level of
.Dq crit
or higher.