SYSLOG.CONF(5) FreeBSD File Formats Manual SYSLOG.CONF(5)
NAME
syslog.conf - syslogd(8) configuration file
DESCRIPTION
The syslog.conf file is the configuration file for the syslogd(8)
program. It consists of blocks of lines separated by program, hostname
or property-based filter specifications (separations appear alone on
their lines), 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 or
spaces.
A special include keyword can be used to include all files with names
ending in '.conf' and not beginning with a '.' contained in the directory
following the keyword. This keyword can only be used in the first level
configuration file.
Note that if you use spaces as separators, your syslog.conf might be
incompatible with other Unices or Unix-like systems. This functionality
was added for ease of configuration (e.g., it is possible to cut-and-
paste into syslog.conf), and to avoid possible mistakes. This change
however preserves backwards compatibility with the old style of
syslog.conf (i.e., tab characters only).
The selectors are encoded as a facility, a period ("."), an optional set
of comparison flags ([!] [<=>]), and a level, with no intervening white-
space. Both the facility and the level are case insensitive.
The facility describes the part of the system generating the message, and
is one of the following keywords: auth, authpriv, console, cron, daemon,
ftp, kern, lpr, mail, mark, news, ntp, security, syslog, user, uucp, and
local0 through local7. These keywords (with the exception of mark)
correspond to similar "LOG_" values specified to the openlog(3) and
syslog(3) library routines.
The comparison flags may be used to specify exactly what is logged. The
default comparison is "=>" (or, if you prefer, ">="), which means that
messages from the specified facility list, and of a priority level equal
to or greater than level will be logged. Comparison flags beginning with
"!" will have their logical sense inverted. Thus "!=info" means all
levels except info and "!notice" has the same meaning as "<notice".
The level describes the severity of the message, and is a keyword from
the following ordered list (higher to lower): emerg, alert, crit, err,
warning, notice, info and debug. These keywords correspond to similar
"LOG_" values specified to the syslog(3) library routine.
Each block of lines is separated from the previous block by a program,
hostname or property-based filter specification. A block will only log
messages corresponding to the most recent program, hostname and
property-based filter specifications given. Thus, with a block which
selects `ppp' as the program, directly followed by a block that selects
messages from the hostname `dialhost', the second block will only log
messages from the ppp(8) program on dialhost.
A program specification is a line beginning with `#!prog' or `!prog' (the
former is for compatibility with the previous syslogd, if one is sharing
syslog.conf files, for example) and the following blocks will be
associated with calls to syslog(3) from that specific program. A program
specification for `foo' will also match any message logged by the kernel
with the prefix `foo: '. The `#!+prog' or `!+prog' specification works
just like the previous one, and the `#!-prog' or `!-prog' specification
will match any message but the ones from that program. Multiple programs
may be listed, separated by commas: `!prog1,prog2' matches messages from
either program, while `!-prog1,prog2' matches all messages but those from
`prog1' or `prog2'.
A hostname specification of the form `#+hostname' or `+hostname' means
the following blocks will be applied to messages received from the
specified hostname. Alternatively, the hostname specification
`#-hostname' or `-hostname' causes the following blocks to be applied to
messages from any host but the one specified. If the hostname is given
as `@', the local hostname will be used. As for program specifications,
multiple comma-separated values may be specified for hostname
specifications.
A property-based filter specification is a line beginning with `#:' or
`:' and the following blocks will be applied only when filter value
matches given filter propertie's value. See PROPERTY-BASED FILTERS
section for more details.
A program, hostname or property-based filter specification may be reset
by giving `*' as an argument.
See syslog(3) for further descriptions of both the facility and level
keywords and their significance. It is preferred 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 does not exist.
If a received message matches the specified facility and is of the
specified 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
all programs.
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 five forms:
• A pathname (beginning with a leading slash). Selected messages are
appended to the file.
To ensure that kernel messages are written to disk promptly,
syslog.conf calls fsync(2) after writing messages from the kernel.
Other messages are not synced explicitly. You may prefix a pathname
with the minus sign, "-", to forego syncing the specified file after
every kernel message. Note that you might lose information if the
system crashes immediately following a write attempt. Nevertheless,
using the "-" option may improve performance, especially if the
kernel is logging many messages.
• A hostname (preceded by an at ("@") sign). Selected messages are
forwarded to the syslogd(8) program on the named host. If a port
number is added after a colon (`:') then that port will be used as
the destination port rather than the usual syslog port. IPv6
addresses can be used by surrounding the address portion with square
brackets (`[' and `]').
• A comma separated list of users. Selected messages are written to
those users if they are logged in.
• An asterisk. Selected messages are written to all logged-in users.
• A vertical bar ("|"), followed by a command to pipe the selected
messages to. The command is passed to sh(1) for evaluation, so usual
shell metacharacters or input/output redirection can occur. (Note
however that redirecting stdio(3) buffered output from the invoked
command can cause additional delays, or even lost output data in case
a logging subprocess exited with a signal.) The command itself runs
with stdout and stderr redirected to /dev/null. Upon receipt of a
SIGHUP, syslogd(8) will close the pipe to the process. If the
process did not exit voluntarily, it will be sent a SIGTERM signal
after a grace period of up to 60 seconds.
The command will only be started once data arrives that should be
piped to it. If it exited later, it will be restarted as necessary.
So if it is desired that the subprocess should get exactly one line
of input only (which can be very resource-consuming if there are a
lot of messages flowing quickly), this can be achieved by exiting
after just one line of input. If necessary, a script wrapper can be
written to this effect.
Unless the command is a full pipeline, it is probably useful to start
the command with exec so that the invoking shell process does not
wait for the command to complete. Warning: the process is started
under the UID invoking syslogd(8), normally the superuser.
Blank lines and lines whose first non-blank character is a hash ("#")
character are ignored. If `#' is placed in the middle of the line, the
`#' character and the rest of the line after it is ignored. To prevent
special meaning, the `#' character may be escaped with `\'; in this case
preceding `\' is removed and `#' is treated as an ordinary character.
PROPERTY-BASED FILTERS
program, hostname specifications performs exact match filtering against
explicit field only. Property-based filters feature substring and
regular expressions (see re_format(7)) matching against various message
attributes. Filter specification starts with `#:' or `:' followed by
three comma-separated fields property, operator, "value". Value must be
double-quoted. A double quote and backslash must be escaped by a
backslash.
Following properties are supported as test value:
• `msg' - body of the message received.
• `programname' - program name sent the message
• `hostname' - hostname of message's originator
• `source' - an alias for hostname
Operator specifies a comparison function between propertie's
value against filter's value. Possible operators:
• `contains' - true if filter value is found as a substring of property
• `isequal' - true if filter value is equal to property
• `startswith' - true if property starts with filter value
• `regex' - true if property matches basic regular expression defined
in filter value
• `ereregex' - true if property matches extended regular expression
defined in filter value
Operator may be prefixed by
• `!' - to invert compare logic
• `icase_' - to make comparison function case insensitive
IMPLEMENTATION NOTES
The "kern" facility is usually reserved for messages generated by the
local kernel. Other messages logged with facility "kern" are usually
translated to facility "user". This translation can be disabled; see
syslogd(8) for details.
FILES
/etc/syslog.conf syslogd(8) configuration file
EXAMPLES
A configuration file might appear as follows:
# Log all kernel messages, authentication messages of
# level notice or higher, and anything of level err or
# higher to the console.
# Do not log private authentication messages!
*.err;kern.*;auth.notice;authpriv.none;mail.crit /dev/console
# Log anything (except mail) of level info or higher.
# Do not log private authentication messages!
*.info;mail.none;authpriv.none /var/log/messages
# Log daemon messages at debug level only
daemon.=debug /var/log/daemon.debug
# 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
# Save mail and news errors of level err and higher in a
# special file.
uucp,news.crit /var/log/spoolerr
# Pipe all authentication messages to a filter.
auth.* |exec /usr/local/sbin/authfilter
# Log all security messages to a separate file.
security.* /var/log/security
# Log all writes to /dev/console to a separate file.
console.* /var/log/console.log
# Save ftpd transactions along with mail and news
!ftpd
*.* /var/log/spoolerr
# Log ipfw messages without syncing after every message.
!ipfw
*.* -/var/log/ipfw
# Log ipfw messages with "Deny" in the message body.
:msg, contains, ".*Deny.*"
*.* /var/log/ipfw.deny
# Reset program name filtering
!*
# Log messages from bird or bird6 into one file
:programname, regex, "^bird6?$"
*.* /var/log/bird-all.log
# Log messages from servers in racks 10-19 in multiple locations, case insensitive
:hostname, icase_ereregex, "^server-(dcA|podB|cdn)-rack1[0-9]{2}\..*"
*.* /var/log/racks10..19.log
SEE ALSO
syslog(3), syslogd(8)
BUGS
The effects of multiple selectors are sometimes not intuitive. For
example "mail.crit,*.err" will select "mail" facility messages at the
level of "err" or higher, not at the level of "crit" or higher.
In networked environments, note that not all operating systems implement
the same set of facilities. The facilities authpriv, cron, ftp, and ntp
that are known to this implementation might be absent on the target
system. Even worse, DEC UNIX uses facility number 10 (which is authpriv
in this implementation) to log events for their AdvFS file system.
FreeBSD 13.1-RELEASE-p6 December 10, 2020 FreeBSD 13.1-RELEASE-p6
man2web Home...