SYSLOG.CONF(5) BSD File Formats Manual SYSLOG.CONF(5)
syslog.conf -- syslogd(8) configuration file
The syslog.conf file is the configuration file for the syslogd(8) pro-
gram. It consists of blocks of lines separated by program specifica-
tions, with each line containing two fields: the selector field which
specifies the types of messages and priorities to which the line applies,
and an action field which specifies the action to be taken if a message
syslogd(8) receives matches the selection criteria. The selector field
is separated from the action field by one or more tab characters.
The selectors are encoded as a facility, a period ('.'), and a level,
with no intervening whitespace. Both the facility and the level are case
The 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 ``LOG_'' values specified to the openlog(3) and syslog(3) library
The 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 simi-
lar (LOG_) values specified to the syslog(3) library routine.
Each block of lines is separated from the previous block by a tag. The
tag is a line beginning with !prog and each block will be associated with
calls to syslog from that specific program. When a message matches mul-
tiple 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 (at least until a tag is found).
!!prog causes the subsequent block to abort evaluation when a message
matches, ensuring that only a single set of actions is taken. !* can be
used to ensure that any ensuing blocks are further evaluated (i.e. can-
celling the effect of a !prog or !!prog).
See syslog(3) for further descriptions of both the facility and level
keywords and their significance. It's recommended that selections be
made on facility rather than program, since the latter can easily vary in
a networked environment. In some cases, though, an appropriate facility
simply doesn't exist.
If a received message matches the specified facility and is of the speci-
fied level (or a higher level), and the first word in the message after
the date matches the program, the action specified in the action field
will be taken.
Multiple selectors may be specified for a single action by separating
them with semicolon (';') characters. It is important to note, however,
that each selector can modify the ones preceding it.
Multiple facilities may be specified for a single level by separating
them with comma (',') characters.
An asterisk ('*') can be used to specify all facilities, all levels or
The special facility ``mark'' receives a message at priority ``info''
every 20 minutes (see syslogd(8)). This is not enabled by a facility
field containing an asterisk.
The special level ``none'' disables a particular facility.
The action field of each line specifies the action to be taken when the
selector field selects a message. There are six forms:
o A pathname (beginning with a leading slash). Selected messages are
appended to the file.
o 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, syslogd(8) tries to
o A hostname (preceded by an at ('@') sign). Selected messages are
forwarded to the syslogd(8) program on the named host. A port number
may be specified using the 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 ('[' and
']'). 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:// or tls:// send messages over TCP or TLS,
respectively, with an optional IP version 4 or 6.
o A comma separated list of users. Selected messages are written to
those users if they are logged in.
o An asterisk. Selected messages are written to all logged-in users.
o A colon, followed by a memory buffer size (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 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.
Blank lines and lines whose first non-blank character is a hash ('#')
character are ignored.
/etc/syslog.conf The syslogd(8) configuration file.
A configuration file might appear as follows:
# Log info (and higher) messages from spamd only to
# a dedicated file, discarding debug messages.
# Matching messages abort evaluation of further rules.
# 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!
# Log anything (except mail) of level info or higher.
# Don't log private authentication messages!
# The authpriv file has restricted access.
# Log all the mail messages in one place.
# Everybody gets emergency messages, plus log them on another
# Root and Eric get alert and higher messages.
# Save mail and news errors of level err and higher in a
# special file.
# Save ftpd transactions along with mail and news
# Keep a copy of all logging in a 32k memory buffer named "debug"
# Store notices and authpriv messages in a 64k buffer named "important"
# feed everything to logsurfer
syslog(3), syslogc(8), syslogd(8)
The syslog.conf file appeared in 4.3BSD, along with syslogd(8).
The effects of multiple selectors are sometimes not intuitive. For exam-
ple ``mail.crit;*.err'' will select ``mail'' facility messages at the
level of ``err'' or higher, not at the level of ``crit'' or higher.
BSD March 30, 2017 BSD