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RSYSLOG.CONF(5) Linux System Administration RSYSLOG.CONF(5)
NAME
rsyslog.conf - rsyslogd(8) configuration file
DESCRIPTION
The rsyslog.conf file is the main configuration file for the rsyslogd(8) which logs system messages on *nix systems.
This file specifies rules for logging. For special features see the rsyslogd(8) manpage. Rsyslog.conf is backward-com-
patible with sysklogd's syslog.conf file. So if you migrate from sysklogd you can rename it and it should work.
Note that this version of rsyslog ships with extensive documentation in html format. This is provided in the ./doc sub-
directory and probably in a separate package if you installed rsyslog via a packaging system. To use rsyslog's advanced
features, you need to look at the html documentation, because the man pages only cover basic aspects of operation.
MODULES
Rsyslog has a modular design. Consequently, there is a growing number of modules. See the html documentation for their
full description.
omsnmp SNMP trap output module
omgssapi
Output module for GSS-enabled syslog
ommysql
Output module for MySQL
omrelp Output module for the reliable RELP protocol (prevents message loss). For details, see below at imrelp and the
html documentation. It can be used like this:
*.* :omrelp:server:port
*.* :omrelp:192.168.0.1:2514 # actual sample
ompgsql
Output module for PostgreSQL
omlibdbi
Generic database output module (Firebird/Interbase, MS SQL, Sybase, SQLite, Ingres, Oracle, mSQL)
imfile Input module for text files
imudp Input plugin for UDP syslog. Replaces the deprecated -r option. Can be used like this:
$ModLoad imudp
$UDPServerRun 514
imtcp Input plugin for plain TCP syslog. Replaces the deprecated -t option. Can be used like this:
$ModLoad imtcp
$InputTCPServerRun 514
imrelp Input plugin for the RELP protocol. RELP can be used instead of UDP or plain TCP syslog to provide reliable
delivery of syslog messages. Please note that plain TCP syslog does NOT provide truly reliable delivery,
with it messages may be lost when there is a connection problem or the server shuts down. RELP prevents
message loss in those cases. It can be used like this:
$ModLoad imrelp
$InputRELPServerRun 2514
imgssapi
Input plugin for plain TCP and GSS-enable syslog
immark Support for mark messages
imklog Kernel logging. To include kernel log messages, you need to do
$ModLoad imklog
Please note that the klogd daemon is no longer necessary and consequently no longer provided by the rsyslog
package.
imuxsock
Unix sockets, including the system log socket. You need to specify
$ModLoad imudp
in order to receive log messages from local system processes. This config directive should only left out if
you know exactly what you are doing.
BASIC STRUCTURE
Lines starting with a hash mark ('#') and empty lines are ignored. Rsyslog.conf should contain following sections
(sorted by recommended order in file):
Global directives
Global directives set some global properties of whole rsyslog daemon, for example size of main message
queue ($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.
Templates
Templates allow you to specify format of the logged message. They are also used for dynamic file name gen-
eration. 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 sepa-
rated by one or more spaces or tabs. The selector field specifies a pattern of facilities and priorities
belonging to the specified action.
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, 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 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. Rsyslogd behaves the same, but has some extensions.
In addition to the above mentioned names the rsyslogd(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 key-
word 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 (',') opera-
tor. You may specify as much 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.
Rsyslogd 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 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.
Regular file
Typically messages are logged to real files. The file has to be specified with full pathname, beginning with a
slash ('/').
Example:
*.* /var/log/traditionalfile.log;RSYSLOG_TraditionalFormat # log to a file in the traditional for-
mat
Note: if you would like to use high-precision timestamps in your log files, just remove the ";RSYSLOG_Traditional-
Format". That will select the default template, which, if not changed, uses RFC 3339 timestamps.
Example:
*.* /var/log/file.log # log to a file with RFC3339 timestamps
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.
Terminal and console
If the file you specified is a tty, special tty-handling is done, same with /dev/console.
Remote machine
There are three ways to forward message: the traditional UDP transport, which is extremely lossy but standard, the
plain TCP based transport which loses messages only during certain situations but is widely available and the RELP
transport which does not lose messages but is currently available only as part of rsyslogd 3.15.0 and above.
To forward messages to another host via UDP, prepend the hostname with the at sign ("@"). To forward it via plain
tcp, prepend two at signs ("@@"). To forward via RELP, prepend the string ":omrelp:" in front of the hostname.
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. Due to the nature of UDP, you will probably lose some messages in transit. If you expect high traffic vol-
ume, you can expect to lose a quite noticeable number of messages (the higher the traffic, the more likely and
severe is message loss).
If you would like to prevent message loss, use RELP:
*.* :omrelp:192.168.0.1:2514
Note that a port number was given as there is no standard port for relp.
Keep in mind that you need to load the correct input and output plugins (see "Modules" above).
Please note that rsyslogd offers a variety of options in regarding to remote forwarding. For full details, please
see the html documentation.
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 com-
mas (','). 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 ('*').
Database table
This allows logging of the message to a database table. 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.
See the html documentation for further details on database logging.
Discard
If the discard action is carried out, the received message is immediately discarded. Discard can be highly effec-
tive 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 $-sign, e.g. if you would like to bind your output channel definition "mychannel" to the action, use "$mychan-
nel". Output channels support template definitions like all all other actions.
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.
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 three different types "filter conditions":
* "traditional" severity and facility based selectors
* property-based filters
* expression-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 pro-
gram on dialhost.
Selectors
Selectors are the traditional way of filtering syslog messages. They have been kept in rsyslog with their origi-
nal syntax, because it is well-known, highly effective and also needed for compatibility with stock syslogd con-
figuration 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.
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 prop-
erty 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.
Expression-Based Filters
See the html documentation for this feature.
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 hard-
coded 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:
$template MyTemplateName,"\7Text %property% some more text\n",<options>
The "$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 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:
% = \%
\ = \\ --> '\' is used to escape (as in C)
$template TraditionalFormat,"%timegenerated% %HOSTNAME% %syslogtag%%msg%0
Properties can be accessed by the property replacer (see there for details).
Please note that 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 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:
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).
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 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. 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 sys-
tem you might notice it ;)
The default template for the write to database action has the sql option set.
Template examples
Please note that the samples are split across multiple lines. A template MUST NOT actually be split across multi-
ple 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%,%timegenerated%,%HOSTNAME%,
%syslogtag%,%msg%0
A template for RFC 3164 format:
$template RFC3164fmt,"<%PRI%>%TIMESTAMP% %HOSTNAME% %syslogtag%%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%', '%timegener-
ated:::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 template.
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 config-
uration file syntax 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
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 param-
eter 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:
*.* $mychannel
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 charac-
ters 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]", program-
name 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. "syslog.info")
IUT the monitorware InfoUnitType - used when talking to a MonitorWare backend (also for phpLogCon)
syslogfacility
the facility from the message - in numerical form
syslogfacility-text
the facility from the message - in text form
syslogseverity
severity from the message - in numerical form
syslogseverity-text
severity from the message - in text form
timegenerated
timestamp when the message was RECEIVED. Always in high resolution
timereported
timestamp from the message. Resolution depends on what was provided 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-syslog-protocol
MSGID The contents of the MSGID field from IETF draft draft-ietf-syslog-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 $-sign are so-called system properties. These do NOT stem from the message but are
rather internally-generated.
Character Positions
FromChar and toChar are used to build substrings. They specify the offset within the string that should be copied.
Offset counting starts at 1, so if you need to obtain the first 2 characters of the message text, you can use this
syntax: "%msg:1:2%". If you do not wish to specify from and to, but you want to specify options, you still need to
include the colons. For example, if you would like to convert the full message text to lower case, use
"%msg:::lowercase%". If you would like to extract from a position until the end of the string, you can place a
dollar-sign ("$") in toChar (e.g. %msg:10:$%, which will extract from position 10 to the end of the string).
There is also support for regular 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
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 cur-
rent 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).
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 useful 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 tabula-
tor would be replaced by "#009".
space-cc
replace control characters by spaces
drop-cc
drop control characters - the resulting string will neither contain control characters, escape sequences
nor any other replacement character like space.
QUEUED OPERATIONS
Rsyslogd supports queued operations to handle offline outputs (like remote syslogd's or database servers being
down). When running in queued mode, rsyslogd buffers messages to memory and optionally to disk (on an as-needed
basis). Queues survive rsyslogd restarts.
It is highly suggested to use remote forwarding and database writing in queued mode, only.
To learn more about queued operations, see the html documentation.
FILES
/etc/rsyslog.conf
Configuration file for rsyslogd
SEE ALSO
rsyslogd(8), logger(1), syslog(3)
The complete documentation can be found in the doc folder of the rsyslog distribution or online at
http://www.rsyslog.com/doc
Please note that the man page reflects only a subset of the configuration options. Be sure to read the html docu-
mentation for all features and details. This is especially vital if you plan to set up a more-then-extremely-sim-
ple system.
AUTHORS
rsyslogd is taken from sysklogd sources, which have been heavily modified by Rainer Gerhards (rgerhards@adis-
con.com) and others.
Version 3.18.0 11 July 2008 RSYSLOG.CONF(5)
