path: root/rsyslog.conf.5

.\" rsyslog.conf - rsyslogd(8) configuration file
.\" Copyright 2003-2007 Rainer Gerhards and Adiscon GmbH.
.\" 
.\" This file is part of the rsyslog  package, an enhanced system log daemon.
.\" 
.\" This program is free software; you can redistribute it and/or modify
.\" it under the terms of the GNU General Public License as published by
.\" the Free Software Foundation; either version 2 of the License, or
.\" (at your option) any later version.
.\" 
.\" This program is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\" 
.\" You should have received a copy of the GNU General Public License
.\" along with this program; if not, write to the Free Software
.\" Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111, USA.
.\"
.TH RSYSLOG.CONF 5 "04 September 2007" "Version 1.19.4" "Linux System Administration"
.SH NAME
rsyslog.conf \- rsyslogd(8) configuration file
.SH DESCRIPTION
The
.I rsyslog.conf
file is the main configuration file for the
.BR rsyslogd (8)
which logs system messages on *nix systems.  This file specifies rules
for logging.  For special features see the
.BR rsyslogd (8)
manpage. Ryslog.conf is backward-compatible with sysklogd's syslog.conf file. So if you migrate
from syklogd you can rename it and it should work.


.SH BASIC STRUCTURE

Lines starting with a hash mark ('#') and empty lines are ignored. 
Rsyslog.conf should contain following sections (sorted by recommended order in file):

.TP
Global directives
Global directives set some global properties of whole rsyslog daemon, for example size of main
message queue ($MainMessageQueueSize), loading external modules ($ModLoad) and so on.
All global directives need to be specified on a line by their own and must start with 
a dollar-sign. The complete list of global directives can be found in html documentation in doc 
directory or online on web pages.

.TP
Templates
Templates allow you to specify format of the logged message. They are also used for dynamic 
file name generation. They have to be defined before they are used in rules. For more info 
about templates see TEMPLATES section of this manpage.

.TP
Output channels
Output channels provide an umbrella for any type of output that the user might want. 
They have to be defined before they are used in rules. For more info about output channels
see OUTPUT CHANNELS section of this manpage.

.TP
Rules (selector + action)
Every rule line 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.

.SH ACTIONS
The action field of a rule describes what to do with the message. In general, message content 
is written to a kind of "logfile". But also other actions might be done, like writing to a 
database table or forwarding to another host.

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

.B Example:
.RS
*.*     /var/log/traditionalfile.log;TraditionalFormat      # log to a file in the traditional format
.RE

.SS Named pipes
This version of rsyslogd(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 rsyslogd(8) is started.

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

.SS Remote machine
To forward messages to another host, prepend the hostname with the at sign ("@").  A single at 
sign means that messages will be forwarded via UDP protocol (the standard for syslog). If you 
prepend two at signs ("@@"), the messages will be transmitted via TCP. 

Please note that this version of rsyslogd by default does NOT forward messages it has received 
from the network to another host. Specify the "-h" option to enable this.

.B Example:
.RS
*.* @192.168.0.1
.RE
.sp
In the example above, messages are forwarded via UDP to the machine 192.168.0.1, the destination 
port defaults to 514. 

.SS 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.

.SS 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 ('*').

.SS Database table
This allows logging of the message to a database table. Currently, only MySQL databases are
supported. By default, a MonitorWare-compatible schema is required for this to work. You can 
create that schema with the createDB.SQL file that came with the rsyslog package. You can also
use any other schema of your liking - you just need to define a proper template and assign this 
template to the action.

The database writer is called by specifying a greater-then sign ('>') in front of the database 
connect information. Immediately after that sign the database host name must be given, a comma, 
the database name, another comma, the database user, a comma and then the user's password. If 
a specific template is to be used, a semicolon followed by the template name can follow the 
connect information. 

.B Example:
.RS
>dbhost,dbname,dbuser,dbpassword;dbtemplate
.RE

.B Important: to use the database functionality, the MySQL output module must be loaded 
in the config file BEFORE the first database table action is used. This is done by placing the
.B $ModLoad 
MySQL directive some place above the first use of the database write (we recommend doing at the 
the beginning of the config file).
.B You have to install the rsyslog-mysql package to get this module.

.SS Discard
If the discard action is carried out, the received message is immediately discarded. Discard 
can be highly effective if you want to filter out some annoying messages that otherwise would 
fill your log files. To do that, place the discard actions early in your log files. 
This often plays well with property-based filters, giving you great freedom in specifying 
what you do not want.

Discard is just the single tilde character with no further parameters.
.sp
.B Example:
.RS
*.*   ~      # discards everything.
.RE


.SS Output channel
Binds an output channel definition (see there for details) to this action. Output channel actions 
must start with a $-sign, e.g. if you would like to bind your output channel definition "mychannel"
to the action, use "$mychannel". Output channels support template definitions like all all other 
actions.

.SS Shell execute
This executes a program in a subshell. The program is passed the template-generated message as the 
only command line parameter. Rsyslog waits until the program terminates and only then continues to run.

.B Example:
.RS
^program-to-execute;template
.RE

The program-to-execute can be any valid executable. It receives the template string as a single parameter 
(argv[1]).

.SH FILTER CONDITIONS
Rsyslog offers two different types "filter conditions":
.sp 0
   * "traditional" severity and facility based selectors
.sp 0
   * property-based filters
.RE

.SS Blocks
Rsyslogd supports BSD-style blocks inside rsyslog.conf. 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, a block which 
selects ‘ppp’ as the program, directly followed by a block that selects messages from the 
hostname ‘dialhost’, then the second block will only log messages from the ppp program on dialhost.

.SS Selectors
.B Selectors are the traditional way of filtering syslog messages. 
They have been kept in rsyslog with their original syntax, because it is well-known, highly 
effective and also needed for compatibility with stock syslogd configuration files. If you just 
need to filter based on priority and facility, you should do this with selector lines. They are 
not second-class citizens in rsyslog and offer the best performance for this job.

.SS Property-Based Filters
Property-based filters are unique to rsyslogd. They allow to filter on any property, like HOSTNAME, 
syslogtag and msg. 

A property-based filter must start with a colon in column 0. This tells rsyslogd that it is the new 
filter type. The colon must be followed by the property name, a comma, the name of the compare 
operation to carry out, another comma and then the value to compare against. This value must be quoted. 
There can be spaces and tabs between the commas. Property names and compare operations are 
case-sensitive, so "msg" works, while "MSG" is an invalid property name. In brief, the syntax is as follows:
.sp
.RS
:property, [!]compare-operation, "value"
.RE

The following compare-operations are currently supported:
.sp
.RS
.B contains
.RS
Checks if the string provided in value is contained in the property
.RE
.sp
.B isequal
.RS
Compares the "value" string provided and the property contents. These two values must be exactly equal to match. 
.RE
.sp
.B startswith
.RS
Checks if the value is found exactly at the beginning of the property value
.RE
.sp
.B regex
.RS 
Compares the property against the provided regular expression.
.RE

.SH TEMPLATES

Every output in rsyslog uses templates - this holds true for files, user 
messages and so on. Templates compatible with the stock syslogd 
formats are hardcoded into rsyslogd. If no template is specified, we use 
one of these hardcoded templates. Search for "template_" in syslogd.c and 
you will find the hardcoded ones.

A template consists of a template directive, a name, the actual template text 
and optional options. A sample is:

.RS
.B $template MyTemplateName,"\\\\7Text %property% some more text\\\\n",<options>
.RE

The "$template" is the template directive. It tells rsyslog that this line 
contains a template. The backslash is an escape character. For example, \\7 rings the 
bell (this is an ASCII value), \\n is a new line. The set in rsyslog is a bit restricted 
currently.

All text in the template is used literally, except for things within percent 
signs. These are properties and allow you access to the contents of the syslog 
message. Properties are accessed via the property replacer and it can for example
pick a substring or do date-specific formatting. More on this is the PROPERTY REPLACER
section of this manpage.

To escape:
.sp 0
   % = \\%
.sp 0
   \\ = \\\\ --> '\\' is used to escape (as in C)
.sp 0
$template TraditionalFormat,%timegenerated% %HOSTNAME% %syslogtag%%msg%\n"

Properties can be accessed by the property replacer (see there for details).

.B Please note that as of 1.15.0, templates can also by used to generate selector lines with dynamic file names.
For example, if you would like to split syslog messages from different hosts 
to different files (one per host), you can define the following template:

.RS
.B $template DynFile,"/var/log/system-%HOSTNAME%.log"
.RE
    
This template can then be used when defining an output selector line. It will 
result in something like "/var/log/system-localhost.log"

.SS Template options
The <options> part is optional. It carries options influencing the template as whole. 
See details below. Be sure NOT to mistake template options with property options - the 
later ones are processed by the property replacer and apply to a SINGLE property, only 
(and not the whole template).

Template options are case-insensitive. Currently defined are:

.RS
.TP 
sql
format the string suitable for a SQL statement in MySQL format. This will replace single 
quotes ("'") and the backslash character by their backslash-escaped counterpart 
("\'" and "\\") inside each field. Please note that in MySQL configuration, the NO_BACKSLASH_ESCAPES 
mode must be turned off for this format to work (this is the default).

.TP 
stdsql
format the string suitable for a SQL statement that is to be sent to a standards-compliant 
sql server. This will replace single quotes ("'") by two single quotes ("''") inside each field. 
You must use stdsql together with MySQL if in MySQL configuration the NO_BACKSLASH_ESCAPES 
is turned on.
.RE

Either the
.B sql
or 
.B stdsql 
option 
.B MUST 
be specified when a template is used for writing to a database, 
otherwise injection might occur. Please note that due to the unfortunate fact 
that several vendors have violated the sql standard and introduced their own 
escape methods, it is impossible to have a single option doing all the work.  
So you yourself must make sure you are using the right format.
.B If you choose the wrong one, you are still vulnerable to sql injection.

Please note that the database writer *checks* that the sql option is present 
in the template. If it is not present, the write database action is disabled. 
This is to guard you against accidental forgetting it and then becoming 
vulnerable to SQL injection. The sql option can also be useful with files - 
especially if you want to import them into a database on another machine for 
performance reasons. However, do NOT use it if you do not have a real need for 
it - among others, it takes some toll on the processing time. Not much, but on 
a really busy system you might notice it ;)

The default template for the write to database action has the sql option set. 
As we currently support only MySQL and the sql option matches the default MySQL 
configuration, this is a good choice. However, if you have turned on 
NO_BACKSLASH_ESCAPES in your MySQL config, you need to supply a template with 
the stdsql option. Otherwise you will become vulnerable to SQL injection. 

.SS Template examples
Please note that the samples are split across multiple lines. A template MUST 
NOT actually be split across multiple lines.

A template that resembles traditional syslogd file output:
.sp
.RS
$template TraditionalFormat,"%timegenerated% %HOSTNAME%
.sp 0
%syslogtag%%msg:::drop-last-lf%\n"
.RE

A template that tells you a little more about the message:
.sp
.RS
$template precise,"%syslogpriority%,%syslogfacility%,%timegenerated%,%HOSTNAME%,
.sp 0
%syslogtag%,%msg%\n"
.RE

A template for RFC 3164 format:
.sp
.RS
$template RFC3164fmt,"<%PRI%>%TIMESTAMP% %HOSTNAME% %syslogtag%%msg%"
.RE

A template for the format traditionally used for user messages:
.sp
.RS
$template usermsg," XXXX%syslogtag%%msg%\n\r"
.RE

And a template with the traditional wall-message format:
.sp
.RS
$template wallmsg,"\\r\\n\\7Message from syslogd@%HOSTNAME% at %timegenerated%"
.RE

.B A template that can be used for writing to a database (please note the SQL template option)
.sp
.RS
.ad l
$template MySQLInsert,"insert iut, message, receivedat values
('%iut%', '%msg:::UPPERCASE%', '%timegenerated:::date-mysql%')
into systemevents\\r\\n", SQL

NOTE 1: This template is embedded into core application under name 
.B StdDBFmt
, so you don't need to define it.
.sp
NOTE 2: You have to have MySQL module installed to use this template.
.ad
.RE

.SH OUTPUT CHANNELS

Output Channels are a new concept first introduced in rsyslog 0.9.0. As of this writing, 
it is most likely that they will be replaced by something different in the future.
 So if you use them, be prepared to change you configuration file syntax when you upgrade 
to a later release.

Output channels are defined via an $outchannel directive. It's syntax is as follows:
.sp
.RS
.B $outchannel name,file-name,max-size,action-on-max-size
.RE

name is the name of the output channel (not the file), file-name is the file name to be 
written to, max-size the maximum allowed size and action-on-max-size a command to be issued 
when the max size is reached. This command always has exactly one parameter. The binary is 
that part of action-on-max-size before the first space, its parameter is everything behind 
that space.

Keep in mind that $outchannel just defines a channel with "name". It does not activate it. 
To do so, you must use a selector line (see below). That selector line includes the channel 
name plus an $ sign in front of it. A sample might be:
.sp
.RS
*.* $mychannel
.RE

.SH PROPERTY REPLACER
The property replacer is a core component in rsyslogd's output system. A syslog message has 
a number of well-defined properties (see below). Each of this properties can be accessed and 
manipulated by the property replacer. With it, it is easy to use only part of a property value 
or manipulate the value, e.g. by converting all characters to lower case.

.SS Accessing Properties
Syslog message properties are used inside templates. They are accessed by putting them between 
percent signs. Properties can be modified by the property replacer. The full syntax is as follows:
.sp
.RS
.B %propname:fromChar:toChar:options%
.RE

propname is the name of the property to access. 
.B It is case-sensitive.

.SS Available Properties
.TP
.B msg
the MSG part of the message (aka "the message" ;))
.TP
.B rawmsg
the message exactly as it was received from the socket. Should be useful for debugging.
.TP
.B HOSTNAME
hostname from the message
.TP
.B FROMHOST
hostname of the system the message was received from (in a relay chain, this is the system immediately 
in front of us and not necessarily the original sender)
.TP
.B syslogtag
TAG from the message
.TP
.B programname
the "static" part of the tag, as defined by BSD syslogd. For example, when TAG is "named[12345]", 
programname is "named".
.TP
.B PRI
PRI part of the message - undecoded (single value)
.TP
.B PRI-text
the PRI part of the message in a textual form (e.g. "syslog.info")
.TP
.B IUT
the monitorware InfoUnitType - used when talking to a MonitorWare backend (also for phpLogCon)
.TP
.B syslogfacility
the facility from the message - in numerical form
.TP
.B syslogfacility-text
the facility from the message - in text form
.TP
.B syslogseverity
severity from the message - in numerical form
.TP
.B syslogseverity-text
severity from the message - in text form
.TP
.B timegenerated
timestamp when the message was RECEIVED. Always in high resolution
.TP
.B timereported
timestamp from the message. Resolution depends on what was provided in the message (in most cases, only seconds)
.TP
.B TIMESTAMP
alias for timereported
.TP
.B PROTOCOL-VERSION
The contents of the PROTOCOL-VERSION field from IETF draft draft-ietf-syslog-protocol
.TP
.B STRUCTURED-DATA
The contents of the STRUCTURED-DATA field from IETF draft draft-ietf-syslog-protocol
.TP
.B APP-NAME
The contents of the APP-NAME field from IETF draft draft-ietf-syslog-protocol
.TP
.B PROCID
The contents of the PROCID field from IETF draft draft-ietf-syslog-protocol
.TP
.B MSGID
The contents of the MSGID field from IETF draft draft-ietf-syslog-protocol
.TP
.B $NOW
The current date stamp in the format YYYY-MM-DD
.TP
.B $YEAR
The current year (4-digit)
.TP
.B $MONTH
The current month (2-digit)
.TP
.B $DAY
The current day of the month (2-digit)
.TP
.B $HOUR
The current hour in military (24 hour) time (2-digit)
.TP
.B $MINUTE
The current minute (2-digit)

.P
Properties starting with a $-sign are so-called system properties. These do NOT stem from the 
message but are rather internally-generated.

.SS Character Positions
FromChar and toChar are used to build substrings. They specify the offset within the string that 
should be copied. Offset counting starts at 1, so if you need to obtain the first 2 characters of 
the message text, you can use this syntax: "%msg:1:2%". If you do not wish to specify from and to, 
but you want to specify options, you still need to include the colons. For example, if you would 
like to convert the full message text to lower case, use "%msg:::lowercase%". If you would like to 
extract from a position until the end of the string, you can place a dollar-sign ("$") in toChar 
(e.g. %msg:10:$%, which will extract from position 10 to the end of the string).

There is also support for 
.Bregular expressions.
To use them, you need to place a "R" into FromChar. 
This tells rsyslog that a regular expression instead of position-based extraction is desired. The 
actual regular expression 
.B must 
then be provided in toChar. The regular expression must be followed 
by the string "--end". It denotes the end of the regular expression and will not become part of it. 
If you are using regular expressions, the property replacer will return the part of the property text 
that matches the regular expression. An example for a property replacer sequence with a regular 
expression is: "%msg:R:.*Sev:. \\(.*\\) \\[.*--end%"

Also, extraction can be done based on so-called "fields". To do so, place a "F" into FromChar. A field 
in its current definition is anything that is delimited by a delimiter character. The delimiter by 
default is TAB (US-ASCII value 9). However, if can be changed to any other US-ASCII character by 
specifying a comma and the decimal US-ASCII value of the delimiter immediately after the "F". For example, 
to use comma (",") as a delimiter, use this field specifier: "F,44".  If your syslog data is delimited, 
this is a quicker way to extract than via regular expressions (actually, a *much* quicker way). Field 
counting starts at 1. Field zero is accepted, but will always lead to a "field not found" error. The same 
happens if a field number higher than the number of fields in the property is requested. The field number 
must be placed in the "ToChar" parameter. An example where the 3rd field (delimited by TAB) from the msg 
property is extracted is as follows: "%msg:F:3%". The same example with semicolon as delimiter is 
"%msg:F,59:3%".

Please note that the special characters "F" and "R" are case-sensitive. Only upper case works, lower case 
will return an error. There are no white spaces permitted inside the sequence (that will lead to error 
messages and will NOT provide the intended result).

.SS Property Options
Property options are case-insensitive. Currently, the following options are defined:
.TP
uppercase
convert property to lowercase only
.TP
lowercase
convert property text to uppercase only
.TP
drop-last-lf
The last LF in the message (if any), is dropped. Especially useful for PIX.
.TP
date-mysql
format as mysql date
.TP
date-rfc3164
format as RFC 3164 date
.TP
date-rfc3339
format as RFC 3339 date
.TP
escape-cc
replace control characters (ASCII value 127 and values less then 32) with an escape sequence. The sequence is "#<charval>" where charval is the 3-digit decimal value of the control character. For example, a tabulator would be replaced by "#009".
.TP
space-cc
replace control characters by spaces
.TP
drop-cc
drop control characters - the resulting string will neither contain control characters, escape sequences nor any other replacement character like space.

.SH FILES
.PD 0
.TP
.I /etc/rsyslog.conf
Configuration file for
.B rsyslogd

.SH SEE ALSO
.BR rsyslogd (8),
.BR logger (1),
.BR syslog (3)

The complete documentation can be found in the doc folder of the rsyslog distribution or online at

.RS
.B    http://www.rsyslog.com/doc
.RE

.SH AUTHORS
The
.B rsyslogd
is taken from sysklogd sources, which have been heavily modified
by Rainer Gerhards (rgerhards@adiscon.com) and others.