syslog.conf

SYSLOG.CONF(5)            Linux System Administration           SYSLOG.CONF(5)



NAME
       syslog.conf - syslogd(8) configuration file

DESCRIPTION
       The syslog.conf file is the main configuration file for the syslogd(8)
       which logs system messages on *nix systems.  This file specifies rules
       for logging.  For special features see the sysklogd(8) manpage.

       Every rule consists of two fields, a selector field and an action
       field.  These two fields are separated by one or more spaces or tabs.
       The selector field specifies a pattern of facilities and priorities
       belonging to the specified action.

       Lines starting with a hash mark (``#'') and empty lines are ignored.

       This release of syslogd is able to understand an extended syntax.  One
       rule can be divided into several lines if the leading line is
       terminated with an backslash (``\'').

SELECTORS
       The selector field itself again consists of two parts, a facility and a
       priority, separated by a period (``.'').  Both parts are case
       insensitive and can also be specified as decimal numbers, but don't do
       that, you have been warned.  Both facilities and priorities are
       described in syslog(3).  The names mentioned below correspond to the
       similar LOG_-values in /usr/include/syslog.h.

       The facility is one of the following keywords: auth, authpriv, cron,
       daemon, ftp, kern, lpr, mail, mark, news, security (same as auth),
       syslog, user, uucp and local0 through local7.  The keyword security
       should not be used anymore and mark is only for internal use and
       therefore should not be used in applications.  Anyway, you may want to
       specify and redirect these messages here.  The facility specifies the
       subsystem that produced the message, i.e. all mail programs log with
       the mail facility (LOG_MAIL) if they log using syslog.

       In most cases anyone can log to any facility, so we rely on convention
       for the correct facility to be chosen.  However, generally only the
       kernel can log to the "kern" facility.  This is because the
       implementation of openlog() and syslog() in glibc does not allow
       logging to the "kern" facility.  Klogd circumvents this restriction
       when logging to syslogd by reimplementing those functions itself.

       The priority is one of the following keywords, in ascending order:
       debug, info, notice, warning, warn (same as warning), err, error (same
       as err), crit, alert, emerg, panic (same as emerg).  The keywords warn,
       error and panic are deprecated and should not be used anymore.  The
       priority defines the severity of the message

       The behavior of the original BSD syslogd is that all messages of the
       specified priority and higher are logged according to the given action.
       This syslogd(8) behaves the same, but has some extensions.

       In addition to the above mentioned names the syslogd(8) understands the
       following extensions: An asterisk (``*'') stands for all facilities or
       all priorities, depending on where it is used (before or after the
       period).  The keyword none stands for no priority of the given
       facility.

       You can specify multiple facilities with the same priority pattern in
       one statement using the comma (``,'') operator.  You may specify as
       many facilities as you want.  Please note that only the facility part
       from such a statement is taken, a priority part would be skipped.

       Multiple selectors may be specified for a single action using the
       semicolon (``;'') separator.  Please note that each selector in the
       selector field is capable of overwriting the preceding ones.  Using
       this behavior you can exclude some priorities from the pattern.

       This syslogd(8) has a syntax extension to the original BSD source,
       which makes its use more intuitive.  You may precede every priority
       with an equation sign (``='') to specify that syslogd should only refer
       to this single priority and not this priority and all higher
       priorities.

       You may also precide the priority with an exclamation mark (``!'') if
       you want syslogd to ignore this priority and all higher priorities.
       You may even use both, the exclamation mark and the equation sign if
       you want syslogd to ignore only this single priority.  If you use both
       extensions than the exclamation mark must occur before the equation
       sign, just use it intuitively.

ACTIONS
       The action field of a rule describes the abstract term ``logfile''.  A
       ``logfile'' need not to be a real file, btw.  The syslogd(8) provides
       the following actions.


   Regular File
       Typically messages are logged to real files.  The file has to be
       specified with full pathname, beginning with a slash ``/''.

       You may prefix each entry with the minus ``-'' sign to omit syncing the
       file after every logging.  Note that you might lose information if the
       system crashes right behind a write attempt.  Nevertheless this might
       give you back some performance, especially if you run programs that use
       logging in a very verbose manner.


   Named Pipes
       This version of syslogd(8) has support for logging output  to named
       pipes (fifos).  A fifo or named pipe can be used as a destination for
       log messages by prepending a pipe symbol (``|'') to the name of the
       file.  This is handy for debugging.  Note that the fifo must be created
       with the mkfifo(1) command  before syslogd(8) is started.


   Terminal and Console
       If the file you specified is a tty, special tty-handling is done, same
       with /dev/console.


   Remote Machine
       This syslogd(8) provides full remote logging, i.e. is able to send
       messages to a remote host running syslogd(8) and to receive messages
       from remote hosts.  The remote host won't forward the message again, it
       will just log them locally.  To forward messages to another host,
       prepend the hostname with the at sign (``@'').

       Using this feature you're able to control all syslog messages on one
       host, if all other machines will log remotely to that.  This tears down
       administration needs.


   List of Users
       Usually critical messages are also directed to ``root'' on that
       machine.  You can specify a list of users that shall get the message by
       simply writing the username.  You may specify more than one user by
       separating the usernames with commas (``,'').  If they're logged in
       they will receive the log messages.


   Everyone logged on
       Emergency messages often go to all users currently online to notify
       them that something strange is happening with the system.  To specify
       this wall(1)-feature use an asterisk (``*'').

EXAMPLES
       Here are some example, partially taken from a real existing site and
       configuration.  Hopefully they rub out all questions on the
       configuration, if not, drop me (Joey) a line.

              # Store critical stuff in critical
              #
              *.=crit;kern.none            /var/adm/critical

       This will store all messages with the priority crit in the file
       /var/adm/critical, except for any kernel message.


              # Kernel messages are first, stored in the kernel
              # file, critical messages and higher ones also go
              # to another host and to the console
              #
              kern.*                       /var/adm/kernel
              kern.crit                    @finlandia
              kern.crit                    /dev/console
              kern.info;kern.!err          /var/adm/kernel-info

       The first rule directs any message that has the kernel facility to the
       file /var/adm/kernel.  (But recall that only the kernel itself can log
       to this facility.)

       The second statement directs all kernel messages of the priority crit
       and higher to the remote host finlandia.  This is useful, because if
       the host crashes and the disks get irreparable errors you might not be
       able to read the stored messages.  If they're on a remote host, too,
       you still can try to find out the reason for the crash.

       The third rule directs these messages to the actual console, so the
       person who works on the machine will get them, too.

       The fourth line tells the syslogd to save all kernel messages that come
       with priorities from info up to warning in the file /var/adm/kernel-
       info.  Everything from err and higher is excluded.


              # The tcp wrapper logs with mail.info, we display
              # all the connections on tty12
              #
              mail.=info                   /dev/tty12

       This directs all messages that uses mail.info (in source LOG_MAIL |
       LOG_INFO) to /dev/tty12, the 12th console.  For example the tcpwrapper
       tcpd(8) uses this as its default.


              # Store all mail concerning stuff in a file
              #
              mail.*;mail.!=info           /var/adm/mail

       This pattern matches all messages that come with the mail facility,
       except for the info priority.  These will be stored in the file
       /var/adm/mail.


              # Log all mail.info and news.info messages to info
              #
              mail,news.=info              /var/adm/info

       This will extract all messages that come either with mail.info or with
       news.info and store them in the file /var/adm/info.


              # Log info and notice messages to messages file
              #
              *.=info;*.=notice;\
                   mail.none  /var/log/messages

       This lets the syslogd log all messages that come with either the info
       or the notice priority into the file /var/log/messages, except for all
       messages that use the mail facility.


              # Log info messages to messages file
              #
              *.=info;\
                   mail,news.none       /var/log/messages

       This statement causes the syslogd to log all messages that come with
       the info priority to the file /var/log/messages.  But any message
       coming either with the mail or the news facility will not be stored.


              # Emergency messages will be displayed using wall
              #
              *.=emerg                     *

       This rule tells the syslogd to write all emergency messages to all
       currently logged in users.  This is the wall action.


              # Messages of the priority alert will be directed
              # to the operator
              #
              *.alert                      root,joey

       This rule directs all messages with a priority of alert or higher to
       the terminals of the operator, i.e. of the users ``root'' and ``joey''
       if they're logged in.


              *.*                          @finlandia

       This rule would redirect all messages to a remote host called
       finlandia.  This is useful especially in a cluster of machines where
       all syslog messages will be stored on only one machine.

CONFIGURATION FILE SYNTAX DIFFERENCES
       Syslogd uses a slightly different syntax for its configuration file
       than the original BSD sources.  Originally all messages of a specific
       priority and above were forwarded to the log file.  The modifiers
       ``='', ``!''  and ``-'' were added to make the syslogd more flexible
       and to use it in a more intuitive manner.

       The original BSD syslogd doesn't understand spaces as separators
       between the selector and the action field.

FILES
       /etc/syslog.conf
              Configuration file for syslogd
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.
SEE ALSO
       sysklogd(8), klogd(8), logger(1), syslog(2), syslog(3).
AUTHORS
       The syslogd is taken from BSD sources, Greg Wettstein
       <greg@wind.enjellic.com> performed the port to Linux, Martin Schulze
       <joey@infodrom.org> fixed some bugs, added several new features and
       took over maintenance.



Version 1.3                    30 November 2006                 SYSLOG.CONF(5)