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SYSLOG.CONF(5)		    BSD File Formats Manual		SYSLOG.CONF(5)

NAME
     syslog.confsyslogd(8) configuration file

DESCRIPTION
     The syslog.conf file is the configuration file for the syslogd(8) pro‐
     gram.  It consists of blocks of lines separated by program and hostname
     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.

     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) cor‐
     respond 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 lev‐
     els 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, crit, alert, 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 or
     hostname specification.  A block will only log messages corresponding to
     the most recent program and hostname 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 associ‐
     ated with calls to syslog(3) from that specific program.  A program spec‐
     ification 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 speci‐
     fied 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 program or hostname specification may be reset by giving the program or
     hostname as ‘*’.

     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 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
     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 ker‐
	 nel 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.

     ·	 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 mes‐
	 sages 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.

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.
     # Don't log private authentication messages!
     *.err;kern.*;auth.notice;authpriv.none;mail.crit	     /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

     # 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

SEE ALSO
     syslog(3), syslogd(8)

BUGS
     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.

     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 sys‐
     tem.  Even worse, DEC UNIX uses facility number 10 (which is authpriv in
     this implementation) to log events for their AdvFS file system.

BSD			       December 23, 2008			   BSD
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