Ubuntu Manpage: rsyslog.conf - rsyslogd(8) configuration file

Provided by: rsyslog_8.16.0-1ubuntu3.1_amd64

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-compatible 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  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.

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 imuxsock

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 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 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 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 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 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 priorities, either exact this one or this and any higher priority. If you use both extensions
than the exclamation mark must occur before the equals 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_TraditionalFileFormat # 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.

Example:
*.* /var/log/file.log # log to a file with RFC3339 timestamps

By default, files are not synced after earch write. To enable syncing of log files globally, use either
the "$ActionFileEnableSync" directive or the "sync" parameter to omfile. Enabling this option degrades
performance and it is advised not to enable syncing unless you know what you are doing. To selectively
disable syncing for certain files, you may prefix the file path with a minus sign ("-").

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 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:
*.* :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 ":omusrmsg:" followed by the login name. You may specify
more than one user by separating them with commas (','). If they're logged in they get the message (for
example: ":omusrmsg:root,user1,user2").

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 ":omusrmsg:*".

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 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 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

Selectors
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.

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:

: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 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 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%\n"

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 system 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 multiple lines.

A template that resembles traditional syslogd file output:

$template TraditionalFormat,"%timegenerated% %HOSTNAME%
%syslogtag%%msg:::drop-last-lf%\n"

A template that tells you a little more about the message:

$template precise,"%syslogpriority%,%syslogfacility%,%timegenerated%,%HOSTNAME%,
%syslogtag%,%msg%\n"

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%\n\r"

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 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 configuration 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 parameter is everything behind that space.

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

              *.* :omfile:$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 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. "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 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).

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 tabulator 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

AUTHORS

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