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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.

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:
error,  warn  and  panic are deprecated and should not be use 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.  Remember 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.  Remember that each selector in  the  selector field  is capable to overwrite 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, that makes its use more intuitively. You may precede every priority with an equation sign (“=”) to specify only this single priority and not  any of  the above. You may also (both is valid, too) precede the priority with an exclamation mark (“!”) to ignore all that priorities, either exact this one or this and any higher 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 login.  You may specify more than one user by separating them with commas (“,”).  If they’re logged  in they  get  the message.  Don’t think a mail would be sent, that might be too late.

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 to 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 direct any message that has the kernel facility  to  the file /var/adm/kernel.

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 loggs 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 it’s 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  finlan-
dia.  This is useful especially in a cluster of machines where all sys-
log messages will be stored on only one machine.

(NOTE): You can also use the IP address of the remote machine in dot notation (xxx.xxx.xxx.xxx) in place of the machine name – this way you can specify a syslog server machine that does NOT have a FQDN [Fully Qualified Domain Name) assigned to it in DNS.

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@linux.de) made some bugfixes and added some new features.