DESCRIPTION
The rsyslog.conf file is the main configuration file for the rsys-
logd(8) which logs system messages on *nix systems. This file speci-
fies rules for logging. For special features see the rsyslogd(8) man-
page. 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.
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):
Global directives
Global directives set some global properties of whole rsyslog
daemon, for example size of main message queue ($MainMessage-
QueueSize), loading external modules ($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.
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.
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.
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 spa-
ces or tabs. The selector field specifies a pattern of facili-
ties and priorities belonging to the specified action.
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 for-
warding to another host.
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.
Terminal and console
If the file you specified is a tty, special tty-handling is done, same
with /dev/console.
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.
Using the $GssMode directive TCP messages can be wrapped with GSS-API.
Example:
*.* @192.168.0.1
In the example above, messages are forwarded via UDP to the machine
192.168.0.1, the destination port defaults to 514.
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 sepa-
rating them with commas (','). If they're logged in they get the mes-
sage. 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 ('*').
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 ('>')
the rsyslog-mysql package to get this module.
Discard
If the discard action is carried out, the received message is immedi-
ately 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.
Example:
*.* ~ # discards everything.
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.
Shell execute
This executes a program in a subshell. The program is passed the tem-
plate-generated message as the only command line parameter. Rsyslog
waits until the program terminates and only then continues to run.
Example:
^program-to-execute;template
The program-to-execute can be any valid executable. It receives the
template string as a single parameter (argv[1]).
FILTER CONDITIONS
Rsyslog offers two different types "filter conditions":
* "traditional" severity and facility based selectors
* property-based filters
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.
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. Prop-
erty names and compare operations are case-sensitive, so "msg" works,
while "MSG" is an invalid property name. In brief, the syntax is as
follows:
:property, [!]compare-operation, "value"
The following compare-operations are currently supported:
contains
Checks if the string provided in value is contained in
the property
isequal
Compares the "value" string provided and the property
contents. These two values must be exactly equal to
match.
startswith
Checks if the value is found exactly at the beginning of
the property value
regex
Compares the property against the provided regular
expression.
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 sys-
logd.c and you will find the hardcoded ones.
A template consists of a template directive, a name, the actual tem-
plate text and optional options. A sample is:
$template MyTemplateName,"\7Text %property% some more
text\n",<options>
The "$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
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:
$template DynFile,"/var/log/system-%HOSTNAME%.log"
This template can then be used when defining an output selector line.
It will result in something like "/var/log/system-localhost.log"
Template options
The <options> part is optional. It carries options influencing the tem-
plate 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:
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 counter-
part ("'" 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).
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.
Either the sql or stdsql option 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 vio-
lated 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. 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
plate MUST NOT actually be split across multiple lines.
A template that resembles traditional syslogd file output:
$template TraditionalFormat,"%timegenerated% %HOSTNAME%
%syslogtag%%msg:::drop-last-lf%0
A template that tells you a little more about the message:
$template precise,"%syslogpriority%,%syslogfacility%,%timegener-
ated%,%HOSTNAME%,
%syslogtag%,%msg%0
A template for RFC 3164 format:
$template RFC3164fmt,"<%PRI%>%TIMESTAMP% %HOSTNAME% %syslog-
tag%%msg%"
A template for the format traditionally used for user messages:
$template usermsg," XXXX%syslogtag%%msg%0r"
And a template with the traditional wall-message format:
$template wallmsg,"\r\n\7Message from syslogd@%HOSTNAME% at
%timegenerated%"
A template that can be used for writing to a database (please note the
SQL template option)
$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 StdDBFmt , so you don't need to define it.
NOTE 2: You have to have MySQL module installed to use this tem-
plate.
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 some-
thing different in the future.
So if you use them, be prepared to change you configuration file syn-
tax when you upgrade to a later release.
Output channels are defined via an $outchannel directive. It's syntax
is as follows:
$outchannel name,file-name,max-size,action-on-max-size
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.
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:
%propname:fromChar:toChar:options%
propname is the name of the property to access. It is case-sensitive.
Available Properties
msg the MSG part of the message (aka "the message" ;))
rawmsg the message exactly as it was received from the socket. Should
be useful for debugging.
HOSTNAME
hostname from the message
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)
syslogtag
TAG from the message
programname
the "static" part of the tag, as defined by BSD syslogd. For
example, when TAG is "named[12345]", programname is "named".
PRI PRI part of the message - undecoded (single value)
PRI-text
the PRI part of the message in a textual form (e.g. "sys-
log.info")
IUT the monitorware InfoUnitType - used when talking to a Monitor-
Ware backend (also for phpLogCon)
syslogfacility
the facility from the message - in numerical form
timereported
timestamp from the message. Resolution depends on what was pro-
vided in the message (in most cases, only seconds)
TIMESTAMP
alias for timereported
PROTOCOL-VERSION
The contents of the PROTOCOL-VERSION field from IETF draft
draft-ietf-syslog-protocol
STRUCTURED-DATA
The contents of the STRUCTURED-DATA field from IETF draft draft-
ietf-syslog-protocol
APP-NAME
The contents of the APP-NAME field from IETF draft draft-ietf-
syslog-protocol
PROCID The contents of the PROCID field from IETF draft draft-ietf-sys-
log-protocol
MSGID The contents of the MSGID field from IETF draft draft-ietf-sys-
log-protocol
$NOW The current date stamp in the format YYYY-MM-DD
$YEAR The current year (4-digit)
$MONTH The current month (2-digit)
$DAY The current day of the month (2-digit)
$HOUR The current hour in military (24 hour) time (2-digit)
$MINUTE
The current minute (2-digit)
Properties starting with a $-sign are so-called system properties.
These do NOT stem from the message but are rather internally-generated.
Character Positions
FromChar and toChar are used to build substrings. They specify the off-
set 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
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 any-
thing 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).
Property Options
Property options are case-insensitive. Currently, the following options
are defined:
uppercase
convert property to lowercase only
lowercase
convert property text to uppercase only
drop-last-lf
The last LF in the message (if any), is dropped. Especially use-
ful for PIX.
date-mysql
format as mysql date
date-rfc3164
format as RFC 3164 date
date-rfc3339
format as RFC 3339 date
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".
rsyslogd(8), logger(1), syslog(3)
The complete documentation can be found in the doc folder of the rsys-
log distribution or online at
http://www.rsyslog.com/doc
AUTHORS
The rsyslogd is taken from sysklogd sources, which have been heavily
modified by Rainer Gerhards (rgerhards@adiscon.com) and others.
Version 1.19.4 04 September 2007 RSYSLOG.CONF(5)
Man(1) output converted with
man2html