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diff --git a/source/configuration/sysklogd_format.rst b/source/configuration/sysklogd_format.rst new file mode 100644 index 0000000..3fd9b8a --- /dev/null +++ b/source/configuration/sysklogd_format.rst @@ -0,0 +1,311 @@ + +*************** +sysklogd format +*************** + +This is the format in use since the beginning of syslogging. It still +is an excellent choice to do very simple things. + +For more advanced things, use the |FmtAdvancedName| format. + +DESCRIPTION +=========== + +The syslog.conf file is the main configuration file for :manpage:`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 variant of syslogd is able to understand a slightly extended syntax +compared to the original BSD syslogd. One rule may be divided into several +lines if the leading line is terminated with an backslash ("\\"). + +SELECTORS +========= + +The selector field 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 corresponding to the definitions in +``/usr/include/syslog.h``. It is safer to use symbolic names rather than +decimal numbers. Both facilities and priorities are described in +:manpage:`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 is deprecated and mark is only +for internal use and therefore should not be used in applications. The facility +specifies the subsystem that produced the message, e.g. 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 +:manpage:`syslogd(8)` behaves the same, but has some extensions. + +In addition to the above mentioned names the :manpage:`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. + +Multiple facilities may be specified for a single priority pattern in one +statement using the comma (",") operator to separate the facilities. 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 ignored. + +Multiple selectors may be specified for a single action using the semicolon +(";") separator. Selectors are processed from left to right, with each selector +being able to overwrite preceding ones. Using this behavior you are able to +exclude some priorities from the pattern. + +This :manpage:`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 precede 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 then 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 :manpage:`syslogd(8)` provides the +following actions. + +Regular File +------------ + +Typically messages are logged to real files. The filename is specified with an +absolute pathname. It may be specified as a file name relative to rsyslog's +working directory if the filename starts with "." or "..". However, this is +dangerous and should be avoided. + +Named Pipes +----------- + +This version of :manpage:`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 +:manpage:`mkfifo(1)` command before :manpage:`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 :manpage:`syslogd(8)` provides full remote logging, i.e. is able to send +messages to a remote host running :manpage:`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 are able to collect all syslog messages on a central +host, if all other machines log remotely to that one. This reduces +administration needs. + +Using a named pipe log method, messages from remote hosts can be sent to a +log program. By reading log messages line by line such a program is able to +sort log messages by host name or program name on the central log host. This +way it is possible to split the log into separate files. + +List of Users +------------- + +Usually critical messages are also directed to "root" on that machine. You can +specify a list of users that ought to receive the log message on the terminal +by writing their usernames. 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 examples, partially taken from a real existing site and +configuration. Hopefully they answer all questions about configuring this +:manpage:`syslogd(8)`. If not, don't hesitate to contact the mailing list. + +:: + + # Store critical stuff in critical + # + *.=crit;kern.none /var/adm/critical + +This will store all messages of priority crit in the file +``/var/adm/critical``, with the exception of any kernel messages. + +:: + + # Kernel messages are 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 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 kernel messages of priority crit and higher 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``. + +This is an example of the 2nd selector overwriting part of the first one. +The first selector selects kernel messages of priority info and higher. The +second selector filters out kernel messages of priority error and higher. +This leaves just priorities info, notice and warning to get logged. + +:: + + # The tcp wrapper logs with mail.info, we display + # all the connections on tty12 + # + mail.=info /dev/tty12 + +This directs all messages that use ``mail.info`` +(in source ``LOG_MAIL | LOG_INFO``) to ``/dev/tty12``, the 12th console. +For example the tcpwrapper :manpage:`tcpd(8)` uses this as its default. + +:: + + # Write all mail related logs to 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 of priority 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. + +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. + +Also, if you specify a selector with an exclamation mark in it which is not +preceded by a corresponding selector without an exclamation mark, nothing +will be logged. Intuitively, the selector "ftp.!alert" on its own will select +all ftp messages with priorities less than alert. In fact it selects nothing. +Similarly "ftp.!=alert" might reasonably be expected to select all ftp messages +other than those with priority alert, but again it selects nothing. It seems +the selectors with exclamation marks in them should only be used as "filters" +following selectors without exclamation marks. + +Finally, using a backslash to divide a line into two doesn't work if the +backslash is used immediately after the end of the selector, without +intermediate whitespace. |