RSYSLOG.CONF(5) Linux System Administration RSYSLOG.CONF(5)
rsyslog.conf - rsyslogd(8) configuration file
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-compatible with sysklogd's sys-
log.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 subdirectory 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.
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
Output module for GSS-enabled syslog
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:192.168.0.1:2514 # actual sample
Output module for PostgreSQL
Generic database output module (Firebird/Interbase, MS SQL, Sybase, SQLite, Ingres,
imfile Input module for text files
imudp Input plugin for UDP syslog. Replaces the deprecated -r option. Can be used like
imtcp Input plugin for plain TCP syslog. Replaces the deprecated -t option. Can be used
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:
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
Please note that the klogd daemon is no longer necessary and consequently no
longer provided by the rsyslog package.
Unix sockets, including the system log socket. You need to specify
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.
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 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 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
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 spaces or tabs. The
selector field specifies a pattern of facilities and priorities belonging to
the specified action.
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 speci-
fied 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 sub-
system 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 pri-
ority 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, depend-
ing 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 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 over-
write the preceding ones. Using this behavior you can exclude some priorities from
Rsyslogd has a syntax extension to the original BSD source, that makes its use more
intuitively. You may precede every priority with an equals 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 priori-
ties, either exact this one or this and any higher priority. If you use both exten-
sions than the exclamation mark must occur before the equals sign, just use it
The action field of a rule describes what to do with the message. In general, mes-
sage 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.
Typically messages are logged to real files. The file has to be specified with full
pathname, beginning with a slash ('/').
*.* /var/log/traditionalfile.log;RSYSLOG_TraditionalFormat # log to
a file in the traditional format
Note: if you would like to use high-precision timestamps in your log files, just
remove the ";RSYSLOG_TraditionalFormat". That will select the default template,
which, if not changed, uses RFC 3339 timestamps.
*.* /var/log/file.log # log to a file with RFC3339 timestamps
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
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
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.
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 volume, 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:
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 "Mod-
Please note that rsyslogd offers a variety of options in regarding to remote for-
warding. 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 commas (','). If they're
logged in they get the message. Don't think a mail would be sent, that might be too
Everyone logged on
Emergency messages often go to all users currently online to notify them that some-
thing strange is happening with the system. To specify this wall(1)-feature use an
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.
If the discard action is carried out, the received message is immediately dis-
carded. 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 fil-
ters, giving you great freedom in specifying what you do not want.
Discard is just the single tilde character with no further parameters.
*.* ~ # discards everything.
Binds an output channel definition (see there for details) to this action. Output
channel actions must start with a $-sign, e.g. if you would like to bind your out-
put channel definition "mychannel" to the action, use "$mychannel". Output channels
support template definitions like all all other actions.
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 termi-
nates and only then continues to run.
The program-to-execute can be any valid executable. It receives the template string
as a single parameter (argv).
Rsyslog offers three different types "filter conditions":
* "traditional" severity and facility based selectors
* property-based filters
* expression-based filters
Rsyslogd supports BSD-style blocks inside rsyslog.conf. Each block of lines is sep-
arated from the previous block by a program or hostname specification. A block will
only log messages corresponding to the most recent program and hostname specifica-
tions 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.
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 effec-
tive 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.
Property-based filters are unique to rsyslogd. They allow to filter on any prop-
erty, 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
:property, [!]compare-operation, "value"
The following compare-operations are currently supported:
Checks if the string provided in value is contained in the property
Compares the "value" string provided and the property contents. These
two values must be exactly equal to match.
Checks if the value is found exactly at the beginning of the property
Compares the property against the provided regular expression.
See the html documentation for this feature.
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:
$template MyTemplateName,"\7Text %property% some more text\n",<options>
The "$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
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.
% = \%
\ = \\ --> '\' 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:
This template can then be used when defining an output selector line. It will
result in something like "/var/log/system-localhost.log"
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 SIN-
GLE 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_BACK-
SLASH_ESCAPES is turned on.
Either the sql or stdsql option MUST be specified when a template is used for writ-
ing 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 system you might notice it
The default template for the write to database action has the sql option set.
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:
$template TraditionalFormat,"%timegenerated% %HOSTNAME%
A template that tells you a little more about the message:
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
$template MySQLInsert,"insert iut, message, receivedat values ('%iut%',
'%msg:::UPPERCASE%', '%timegenerated:::date-mysql%') into systemevents\r\n",
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 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 fol-
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 com-
mand 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 acti-
vate 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:
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 proper-
ties 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.
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 is the name of the property to access. It is case-sensitive.
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
hostname from the message
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
TAG from the message
the "static" part of the tag, as defined by BSD syslogd. For example, when
TAG is "named", programname is "named".
PRI PRI part of the message - undecoded (single value)
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)
the facility from the message - in numerical form
the facility from the message - in text form
severity from the message - in numerical form
severity from the message - in text form
timestamp when the message was RECEIVED. Always in high resolution
timestamp from the message. Resolution depends on what was provided in the
message (in most cases, only seconds)
alias for timereported
The contents of the PROTOCOL-VERSION field from IETF draft draft-ietf-sys-
The contents of the STRUCTURED-DATA field from IETF draft draft-ietf-syslog-
The contents of the APP-NAME field from IETF draft draft-ietf-syslog-proto-
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)
The current minute (2-digit)
Properties starting with a $-sign are so-called system properties. These do NOT
stem from the message but are rather internally-generated.
FromChar and toChar are used to build substrings. They specify the offset within
the string that should be copied. Offset counting starts at 1, so if you need to
obtain the first 2 characters of the message text, you can use this syntax:
"%msg:1:2%". If you do not wish to specify from and to, but you want to specify
options, you still need to include the colons. For example, if you would like to
convert the full message text to lower case, use "%msg:::lowercase%". If you would
like to extract from a position until the end of the string, you can place a dol-
lar-sign ("$") 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 posi-
tion-based extraction is desired. The actual regular expression must then be pro-
vided 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
Property options are case-insensitive. Currently, the following options are
convert property to lowercase only
convert property text to uppercase only
The last LF in the message (if any), is dropped. Especially useful for PIX.
format as mysql date
format as RFC 3164 date
format as RFC 3339 date
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".
replace control characters by spaces
drop control characters - the resulting string will neither contain control
characters, escape sequences nor any other replacement character like space.
Rsyslogd supports queued operations to handle offline outputs (like remote sys-
logd's or database servers being down). When running in queued mode, rsyslogd buf-
fers messages to memory and optionally to disk (on an as-needed basis). Queues sur-
vive rsyslogd restarts.
It is highly suggested to use remote forwarding and database writing in queued
To learn more about queued operations, see the html documentation.
Configuration file for rsyslogd
rsyslogd(8), logger(1), syslog(3)
The complete documentation can be found in the doc folder of the rsyslog distribu-
tion or online at
Please note that the man page reflects only a subset of the configuration options.
Be sure to read the html documentation for all features and details. This is espe-
cially vital if you plan to set up a more-then-extremely-simple system.
rsyslogd is taken from sysklogd sources, which have been heavily modified by Rainer
Gerhards (firstname.lastname@example.org) and others.
Version 3.18.0 11 July 2008 RSYSLOG.CONF(5)