From 47bbd838bdaa200d89d8210a6a0ba9c322129bca Mon Sep 17 00:00:00 2001 From: Tom Bergfeld Date: Fri, 31 Oct 2008 14:47:30 +0100 Subject: restructured rsyslog.conf documentation Signed-off-by: Rainer Gerhards --- doc/rsyslog_conf.html | 1235 +------------------------------------------------ 1 file changed, 21 insertions(+), 1214 deletions(-) (limited to 'doc/rsyslog_conf.html') diff --git a/doc/rsyslog_conf.html b/doc/rsyslog_conf.html index cd3db405..852d95b5 100644 --- a/doc/rsyslog_conf.html +++ b/doc/rsyslog_conf.html @@ -20,257 +20,13 @@ possible. While, for obvious reasons, enhanced features require a different config file syntax, rsyslogd should be able to work with a standard syslog.conf file. This is especially useful while you are migrating from syslogd to rsyslogd.

-

Modules

-

Rsyslog has a modular design. Consequently, there is a growing -number of modules. Here is the entry point to their documentation and -what they do (list is currently not complete)

- -

Please note that each module provides configuration -directives, which are NOT necessarily being listed below. Also -remember, that a modules configuration directive (and functionality) is -only available if it has been loaded (using $ModLoad).

+

Modules

Lines

Lines can be continued by specifying a backslash ("\") as the last character of the line. There is a hard-coded maximum line length of 4K. If you need lines larger than that, you need to change compile-time settings inside rsyslog and recompile. -

Global Directives

-

All global directives need to be specified on a line by their -own and must start with a dollar-sign. Here is a list in alphabetical -order. Follow links for a description.

-

Please note that not all directives here are actually global. Some affect -only the next action. This documentation will be changed soon. -

Not all directives have an in-depth description right now. -Default values for them are in bold. A more in-depth description will -appear as implementation progresses. -

-

Be sure to read information about queues in rsyslog - -many parameter settings modify queue parameters. If in doubt, use the -default, it is usually well-chosen and applicable in most cases.

- -

Where <size_nbr> is specified above, -modifiers can be used after the number part. For example, 1k means -1024. Supported are k(ilo), m(ega), g(iga), t(era), p(eta) and e(xa). -Lower case letters refer to the traditional binary defintion (e.g. 1m -equals 1,048,576) whereas upper case letters refer to their new -1000-based definition (e.g 1M equals 1,000,000).

-

Numbers may include '.' and ',' for readability. So you can -for example specify either "1000" or "1,000" with the same result. -Please note that rsyslogd simply ignores the punctuation. Form it's -point of view, "1,,0.0.,.,0" also has the value 1000.

+

Global Directives

Basic Structure

Rsyslog supports standard sysklogd's configuration file format and extends it. So in general, you can take a "normal" syslog.conf and @@ -289,975 +45,15 @@ priorities belonging to the specified action.

Lines starting with a hash mark ("#'') and empty lines are ignored.

-

Templates

-

Templates are a key feature of rsyslog. They allow to specify -any -format a user might want. They are also used for dynamic file name -generation. Every output in rsyslog uses templates - this holds true -for files, user messages and so on. The database writer expects its -template to be a proper SQL statement - so this is highly customizable -too. You might ask how does all of this work when no templates at all -are specified. Good question ;) The answer is simple, though. Templates -compatible with the stock syslogd formats are hardcoded into rsyslogd. -So 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. "MyTemplateName" is the template -name. All -other config lines refer to this name. The text within quotes is the -actual template text. The backslash is an escape character, much as it -is in C. It does all these "cool" things. For example, \7 rings the -bell (this is an ASCII value), \n is a new line. C programmers and perl -coders have the advantage of knowing this, but 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 (nice name, huh) and it can do cool things, too. For -example, it can pick a substring or do date-specific formatting. More -on this is below, on some lines of the property replacer.
-
-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. As we currently support only MySQL and the sql option -matches the default MySQL configuration, this is a good choice. -However, if you have turned on -NO_BACKSLASH_ESCAPES in -your MySQL config, you need to supply a template with the stdsql -option. Otherwise you will become vulnerable to SQL injection.
-
-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 -names beginning with "RSYSLOG_" are reserved for rsyslog use. Do NOT -use them if, otherwise you may receive a conflict in the future (and -quite unpredictable behaviour). There is a small set of pre-defined -templates that you can use without the need to define it:

- -

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.
-
-The idea behind output channel definitions is that it shall provide an -umbrella for any type of output that the user might want. In essence,
-this is the "file" part of selector lines (and this is why we are not -sure output channel syntax will stay after the next review). There is a
-difference, though: selector channels both have filter conditions -(currently facility and severity) as well as the output destination. -Output channels define the output definition, only. As of this build, -they can only be used to write to files - not pipes, ttys or whatever -else. If we stick with output channels, this will change over time.

-

In concept, an output channel includes everything needed to -know about an output actions. In practice, the current implementation -only carries
-a filename, a maximum file size and a command to be issued when this -file size is reached. More things might be present in future version, -which might also change the syntax of the directive.

-

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.
-
-Please note that max-size is queried BEFORE writing the log message to -the file. So be sure to set this limit reasonably low so that any -message might fit. For the current release, setting it 1k lower than -you expected is helpful. The max-size must always be specified in bytes -- there are no special symbols (like 1k, 1m,...) at this point of -development.
-
-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
-
-In its current form, output channels primarily provide the ability to -size-limit an output file. To do so, specify a maximum size. When this -size is reached, rsyslogd will execute the action-on-max-size command -and then reopen the file and retry. The command should be something -like a log rotation -script or a similar thing.

-

If there is no action-on-max-size command or the command did -not resolve the situation, the file is closed and never reopened by -rsyslogd (except, of course, by huping it). This logic was integrated -when we first experienced severe issues with files larger 2gb, which -could lead to rsyslogd dumping core. In such cases, it is more -appropriate to stop writing to a single file. Meanwhile, rsyslogd has -been fixed to support files larger 2gb, but obviously only on file -systems and operating system versions that do so. So it can still make -sense to enforce a 2gb file size limit.

-

Filter Conditions

-

Rsyslog offers four different types "filter conditions":

- -

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. -

-

A program specification is a line beginning with ‘!prog’ and -the following blocks will be associated with calls to syslog from that -specific program. A program specification for ‘foo’ will also match any -message logged by the kernel with the prefix ‘foo: ’. Alternatively, a -program specification ‘-foo’ causes the following blocks to be applied -to messages from any program but the one specified. A hostname -specification of the form ‘+hostname’ and the following blocks will be -applied to messages received from the specified hostname. -Alternatively, a hostname specification ‘-hostname’ causes the -following blocks to be applied to messages from any host but the one -specified. If the hostname is given as ‘@’, the local hostname will be -used. (NOT YET IMPLEMENTED) A program or hostname specification may be -reset by giving the program or hostname as ‘*’.

-

Please note that the "#!prog", "#+hostname" and "#-hostname" -syntax available in BSD syslogd is not supported by rsyslogd. By -default, no hostname or program is set.

-

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.

-

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 rsyslog(3). The names mentioned below correspond to the -similar LOG_-values in /usr/include/rsyslog.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 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.

-

Property-Based Filters

-

Property-based filters are unique to rsyslogd. They allow to -filter on any property, like HOSTNAME, syslogtag and msg. A list of all -currently-supported properties can be found in the property replacer documentation -(but keep in mind that only the properties, not the replacer is -supported). With this filter, each properties can be checked against a -specified value, using a specified compare operation. Currently, there -is only a single compare operation (contains) available, but additional -operations will be added in the future.

-

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:

- - - - - - - - - - - - - - - - - - - -
containsChecks if the string provided in value is contained in -the property. There must be an exact match, wildcards are not supported.
isequalCompares the "value" string provided and the property -contents. These two values must be exactly equal to match. The -difference to contains is that contains searches for the value anywhere -inside the property value, whereas all characters must be identical for -isequal. As such, isequal is most useful for fields like syslogtag or -FROMHOST, where you probably know the exact contents.
startswithChecks if the value is found exactly at the beginning -of the property value. For example, if you search for "val" with -

:msg, startswith, "val"

-

it will be a match if msg contains "values are in this -message" but it won't match if the msg contains "There are values in -this message" (in the later case, contains would match). Please note -that "startswith" is by far faster than regular expressions. So even -once they are implemented, it can make very much sense -(performance-wise) to use "startswith".

-
regexCompares the property against the provided POSIX -regular -expression.
-

You can use the bang-character (!) immediately in front of a -compare-operation, the outcome of this operation is negated. For -example, if msg contains "This is an informative message", the -following sample would not match:

-

:msg, contains, "error"

-

but this one matches:

-

:msg, !contains, "error"

-

Using negation can be useful if you would like to do some -generic processing but exclude some specific events. You can use the -discard action in conjunction with that. A sample would be:

-

*.* -/var/log/allmsgs-including-informational.log
-:msg, contains, "informational"  ~ -
-*.* /var/log/allmsgs-but-informational.log

-

Do not overlook the red tilde in line 2! In this sample, all -messages are written to the file allmsgs-including-informational.log. -Then, all messages containing the string "informational" are discarded. -That means the config file lines below the "discard line" (number 2 in -our sample) will not be applied to this message. Then, all remaining -lines will also be written to the file allmsgs-but-informational.log.

-

Value is a quoted string. It supports some -escape sequences:

-

\" - the quote character (e.g. "String with \"Quotes\"")
-\\ - the backslash character (e.g. "C:\\tmp")

-

Escape sequences always start with a backslash. Additional -escape sequences might be added in the future. Backslash characters must -be escaped. Any other sequence then those outlined above is invalid and -may lead to unpredictable results.

-

Probably, "msg" is the most prominent use case of property -based filters. It is the actual message text. If you would like to -filter based on some message content (e.g. the presence of a specific -code), this can be done easily by:

-

:msg, contains, "ID-4711"

-

This filter will match when the message contains the string -"ID-4711". Please note that the comparison is case-sensitive, so it -would not match if "id-4711" would be contained in the message.

-

:msg, regex, "fatal .* error"

-

This filter uses a POSIX regular expression. It matches when -the -string contains the words "fatal" and "error" with anything in between -(e.g. "fatal net error" and "fatal lib error" but not "fatal error" as -two spaces are required by the regular expression!).

-

Getting property-based filters right can sometimes be -challenging. In order to help you do it with as minimal effort as -possible, rsyslogd spits out debug information for all property-based -filters during their evaluation. To enable this, run rsyslogd in -foreground and specify the "-d" option.

-

Boolean operations inside property based filters (like -'message contains "ID17" or message contains "ID18"') are currently not -supported (except for "not" as outlined above). Please note that while -it is possible to query facility and severity via property-based -filters, it is far more advisable to use classic selectors (see above) -for those cases.

-

Expression-Based Filters

-Expression based filters allow -filtering on arbitrary complex expressions, which can include boolean, -arithmetic and string operations. Expression filters will evolve into a -full configuration scripting language. Unfortunately, their syntax will -slightly change during that process. So if you use them now, you need -to be prepared to change your configuration files some time later. -However, we try to implement the scripting facility as soon as possible -(also in respect to stage work needed). So the window of exposure is -probably not too long.
-
-Expression based filters are indicated by the keyword "if" in column 1 -of a new line. They have this format:
-
-if expr then action-part-of-selector-line
-
-"If" and "then" are fixed keywords that mus be present. "expr" is a -(potentially quite complex) expression. So the expression documentation for -details. "action-part-of-selector-line" is an action, just as you know -it (e.g. "/var/log/logfile" to write to that file).
-
-A few quick samples:
-
- -*.* /var/log/file1 # the traditional way
-if $msg contains 'error' /var/log/errlog # the expression-based way
- -
-Right now, you need to specify numerical values if you would like to -check for facilities and severity. These can be found in RFC 3164. -If you don't like that, you can of course also use the textual property -- just be sure to use the right one. As expression support is enhanced, -this will change. For example, if you would like to filter on message -that have facility local0, start with "DEVNAME" and have either -"error1" or "error0" in their message content, you could use the -following filter:
-
- -if $syslogfacility-text == 'local0' and $msg -startswith 'DEVNAME' and ($msg contains 'error1' or $msg contains -'error0') then /var/log/somelog
- -
-Please note that the above must -all be on one line! And if you would like to store all -messages except those that contain "error1" or "error0", you just need -to add a "not":
-
- -if $syslogfacility-text == 'local0' and $msg -startswith 'DEVNAME' and not -($msg contains 'error1' or $msg contains -'error0') then /var/log/somelog
- -
-If you would like to do case-insensitive comparisons, use -"contains_i" instead of "contains" and "startswith_i" instead of -"startswith".
-
-Note that regular expressions are currently NOT -supported in expression-based filters. These will be added later when -function support is added to the expression engine (the reason is that -regular expressions will be a separate loadable module, which requires -some more prequisites before it can be implemented).
-

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.
-
-Templates can be used with all actions. If used, the specified template -is used to generate the message content (instead of the default -template). To specify a template, write a semicolon after the action -value immediately followed by the template name.
-
-Beware: templates MUST be defined BEFORE they are used. It is OK to -define some templates, then use them in selector lines, define more -templates and use use them in the following selector lines. But it is -NOT permitted to use a template in a selector line that is above its -definition. If you do this, the action will be ignored.

-

You can have multiple actions for a single selector  (or -more precisely a single filter of such a selector line). Each action -must be on its own line and the line must start with an ampersand -('&') character and have no filters. An example would be

-

*.=crit rger
-& root
-& /var/log/critmsgs

-

These three lines send critical messages to the user rger and -root and also store them in /var/log/critmsgs. Using multiple -actions per selector is convenient and also offers -a performance benefit. As the filter needs to be evaluated -only once, there is less computation required to process the directive -compared to the otherwise-equal config directives below:

-

*.=crit rger
-*.=crit root
-*.=crit /var/log/critmsgs

-

 

-

Regular File

-

Typically messages are logged to real files. The file has to -be specified with full pathname, beginning with a slash "/''.
-
-You may prefix each entry with the minus "-'' sign to omit syncing the -file after every logging. Note that you might lose information if the -system crashes right behind a write attempt. Nevertheless this might -give you back some performance, especially if you run programs that use -logging in a very verbose manner.

-

If your system is connected to a reliable UPS and you receive -lots of log data (e.g. firewall logs), it might be a very good idea to -turn of -syncing by specifying the "-" in front of the file name.

-

The filename can be either static (always -the same) or dynamic (different based on message -received). The later is useful if you would automatically split -messages into different files based on some message criteria. For -example, dynamic file name selectors allow you to split messages into -different files based on the host that sent them. With dynamic file -names, everything is automatic and you do not need any filters.

-

It works via the template system. First, you define a template -for the file name. An example can be seen above in the description of -template. We will use the "DynFile" template defined there. Dynamic -filenames are indicated by specifying a questions mark "?" instead of a -slash, followed by the template name. Thus, the selector line for our -dynamic file name would look as follows:

-
-*.* ?DynFile -
-

That's all you need to do. Rsyslog will now automatically -generate file names for you and store the right messages into the right -files. Please note that the minus sign also works with dynamic file -name selectors. Thus, to avoid syncing, you may use

-
-*.* -?DynFile
-

And of course you can use templates to specify the output -format:

-
-*.* ?DynFile;MyTemplate
-

A word of caution: rsyslog creates files as -needed. So if a new host is using your syslog server, rsyslog will -automatically create a new file for it.

-

Creating directories is also supported. For -example you can use the hostname as directory and the program name as -file name:

-
-$template DynFile,"/var/log/%HOSTNAME%/%programname%.log"
-

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

-

Rsyslogd provides full remote logging, i.e. is able to send -messages to a remote host running rsyslogd(8) and to receive messages -from remote hosts. Using this feature you're able to control all syslog -messages on one host, if all other machines will log remotely to that. -This tears down
-administration needs.
-
-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.

-

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 plain TCP based syslog is not officially standardized, but -most major syslogds support it (e.g. syslog-ng or WinSyslog). The -forwarding action indicator (at-sign) can be followed by one or more -options. If they are given, they must be immediately (without a space) -following the final at sign and be enclosed in parenthesis. The -individual options must be separated by commas. The following options -are right now defined:

- - - - - - - - - - - -
-

z<number>

-		Enable zlib-compression for the message. The -<number> is the compression level. It can be 1 (lowest -gain, lowest CPU overhead) to 9 (maximum compression, highest CPU -overhead). The level can also be 0, which means "no compression". If -given, the "z" option is ignored. So this does not make an awful lot of -sense. There is hardly a difference between level 1 and 9 for typical -syslog messages. You can expect a compression gain between 0% and 30% -for typical messages. Very chatty messages may compress up to 50%, but -this is seldom seen with typically traffic. Please note that rsyslogd -checks the compression gain. Messages with 60 bytes or less will never -be compressed. This is because compression gain is pretty unlikely and -we prefer to save CPU cycles. Messages over that size are always -compressed. However, it is checked if there is a gain in compression -and only if there is, the compressed message is transmitted. Otherwise, -the uncompressed messages is transmitted. This saves the receiver CPU -cycles for decompression. It also prevents small message to actually -become larger in compressed form. -

Please note that when a TCP transport is used, -compression will also turn on syslog-transport-tls framing. See the "o" -option for important information on the implications.

-

Compressed messages are automatically detected and -decompressed by the receiver. There is nothing that needs to be -configured on the receiver side.

-
-

o

-		This option is experimental. Use at your own -risk and only if you know why you need it! If in doubt, do NOT turn it -on. -

This option is only valid for plain TCP based -transports. It selects a different framing based on IETF internet draft -syslog-transport-tls-06. This framing offers some benefits over -traditional LF-based framing. However, the standardization effort is -not yet complete. There may be changes in upcoming versions of this -standard. Rsyslog will be kept in line with the standard. There is some -chance that upcoming changes will be incompatible to the current -specification. In this case, all systems using -transport-tls framing -must be upgraded. There will be no effort made to retain compatibility -between different versions of rsyslog. The primary reason for that is -that it seems technically impossible to provide compatibility between -some of those changes. So you should take this note very serious. It is -not something we do not *like* to do (and may change our mind if enough -people beg...), it is something we most probably *can not* do for -technical reasons (aka: you can beg as much as you like, it won't -change anything...).

-

The most important implication is that compressed syslog -messages via TCP must be considered with care. Unfortunately, it is -technically impossible to transfer compressed records over traditional -syslog plain tcp transports, so you are left with two evil choices...

-
-


-The hostname may be followed by a colon and the destination port.

-

The following is an example selector line with forwarding:

-

*.*    @@(o,z9)192.168.0.1:1470

-

In this example, messages are forwarded via plain TCP with -experimental framing and maximum compression to the host 192.168.0.1 at -port 1470.

-

*.* @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. Messages -will not be compressed.

-

Note that IPv6 addresses contain colons. So if an IPv6 address is specified -in the hostname part, rsyslogd could not detect where the IP address ends -and where the port starts. There is a syntax extension to support this: -put squary brackets around the address (e.g. "[2001::1]"). Square -brackets also work with real host names and IPv4 addresses, too. -

A valid sample to send messages to the IPv6 host 2001::1 at port 515 -is as follows: -

*.* @[2001::1]:515 -

This works with TCP, too. -

Note to sysklogd users: sysklogd does not -support RFC 3164 format, which is the default forwarding template in -rsyslog. As such, you will experience duplicate hostnames if rsyslog is -the sender and sysklogd is the receiver. The fix is simple: you need to -use a different template. Use that one:

-

$template -sysklogd,"<%PRI%>%TIMESTAMP% %syslogtag%%msg%\""
-*.* @192.168.0.1;sysklogd

-

List of Users

-

Usually critical messages are also directed to "root'' on -that machine. You can specify a list of users that shall get the -message by simply writing the login. You may specify more than one user -by separating them with commas (",''). If they're logged in they get -the message. Don't think a mail would be sent, that might be too late.

-

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 ("*'').

-

Call Plugin

-

This is a generic way to call an output plugin. The plugin -must support this functionality. Actual parameters depend on the -module, so see the module's doc on what to supply. The general syntax -is as follows:

-

:modname:params;template

-

Currently, the ommysql database output module supports this -syntax (in addtion to the ">" syntax it traditionally -supported). For ommysql, the module name is "ommysql" and the params -are the traditional ones. The ;template part is not module specific, it -is generic rsyslog functionality available to all modules.

-

As an example, the ommysql module may be called as follows:

-

:ommysql:dbhost,dbname,dbuser,dbpassword;dbtemplate

-

For details, please see the "Database Table" section of this -documentation.

-

Note: as of this writing, the ":modname:" part is hardcoded -into the module. So the name to use is not necessarily the name the -module's plugin file is called.

-

Database Table

-

This allows logging of the message to a database table. -Currently, only MySQL databases are supported. However, other database -drivers will most probably be developed as plugins. By default, a MonitorWare-compatible -schema is required for this to work. You can create that schema with -the createDB.SQL file that came with the rsyslog package. You can also
-use any other schema of your liking - you just need to define a proper -template and assign this template to the action.
-
-The database writer is called by specifying a greater-then sign -(">") in front of the database connect information. Immediately -after that
-sign the database host name must be given, a comma, the database name, -another comma, the database user, a comma and then the user's password. -If a specific template is to be used, a semicolon followed by the -template name can follow the connect information. This is as follows:
-
->dbhost,dbname,dbuser,dbpassword;dbtemplate

-

Important: to use the database functionality, the -MySQL output module must be loaded in the config file BEFORE -the first database table action is used. This is done by placing the

-

$ModLoad ommysql

-

directive some place above the first use of the database write -(we recommend doing at the the beginning of the config file).

-

Discard

-

If the discard action is carried out, the received message is -immediately discarded. No further processing of it occurs. Discard has -primarily been added to filter out messages before carrying on any -further processing. For obvious reasons, the results of "discard" are -depending on where in the configuration file it is being used. Please -note that once a message has been discarded there is no way to retrieve -it in later configuration file lines.

-

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:

-

~

-

For example,

-

*.*   ~

-

discards everything (ok, you can achive the same by not -running rsyslogd at all...).

-

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.

-

^program-to-execute;template

-

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

-

WARNING: The Shell Execute action was added -to serve an urgent need. While it is considered reasonable save when -used with some thinking, its implications must be considered. The -current implementation uses a system() call to execute the command. -This is not the best way to do it (and will hopefully changed in -further releases). Also, proper escaping of special characters is done -to prevent command injection. However, attackers always find smart ways -to circumvent escaping, so we can not say if the escaping applied will -really safe you from all hassles. Lastly, rsyslog will wait until the -shell command terminates. Thus, a program error in it (e.g. an infinite -loop) can actually disable rsyslog. Even without that, during the -programs run-time no messages are processed by rsyslog. As the IP -stacks buffers are quickly overflowed, this bears an increased risk of -message loss. You must be aware of these implications. Even though they -are severe, there are several cases where the "shell execute" action is -very useful. This is the reason why we have included it in its current -form. To mitigate its risks, always a) test your program thoroughly, b) -make sure its runtime is as short as possible (if it requires a longer -run-time, you might want to spawn your own sub-shell asynchronously), -c) apply proper firewalling so that only known senders can send syslog -messages to rsyslog. Point c) is especially important: if rsyslog is -accepting message from any hosts, chances are much higher that an -attacker might try to exploit the "shell execute" action.

-

TEMPLATE NAME

-

Every ACTION can be followed by a template name. If so, that -template is used for message formatting. If no name is given, a -hard-coded default template is used for the action. There can only be -one template name for each given action. The default template is -specific to each action. For a description of what a template is and -what you can do with it, see "TEMPLATES" at the top of this document.

-

EXAMPLES

-

Below are example for templates and selector lines. I hope +

Templates

+

Output Channels

+

Filter Conditions

+

Actions

+

Examples

+

Here you will find examples for templates and selector lines. I hope they are self-explanatory. If not, please see www.monitorware.com/rsyslog/ for advise.

-

TEMPLATES

-

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:
-$template RFC3164fmt,"<%PRI%>%TIMESTAMP% %HOSTNAME% -%syslogtag%%msg%"
-
-A template for the format traditonally used for user messages:
-$template usermsg," XXXX%syslogtag%%msg%\n\r"
-
-And a template with the traditonal wall-message format:
-$template wallmsg,"\r\n\7Message from syslogd@%HOSTNAME% at -%timegenerated%
-
-A template that can be used for the database write (please note the SQL
-template option)
-$template MySQLInsert,"insert iut, message, receivedat values
-('%iut%', '%msg:::UPPERCASE%', '%timegenerated:::date-mysql%')
-into systemevents\r\n", SQL
-
-The following template emulates WinSyslog -format (it's an Adiscon -format, you do not feel bad if you don't know it ;)). It's interesting -to see how it takes different parts out of the date stamps. What -happens is that the date stamp is split into the actual date and time -and the these two are combined with just a comma in between them.
-
-$template WinSyslogFmt,"%HOSTNAME%,%timegenerated:1:10:date-rfc3339%,
-%timegenerated:12:19:date-rfc3339%,%timegenerated:1:10:date-rfc3339%,
-%timegenerated:12:19:date-rfc3339%,%syslogfacility%,%syslogpriority%,
-%syslogtag%%msg%\n"

-

SELECTOR LINES

-

# Store critical stuff in critical
-#
-*.=crit;kern.none /var/adm/critical
-
-This will store all messages with the priority crit in the file -/var/adm/critical, except for any kernel message.
-
-
-# Kernel messages are first, stored in the kernel
-# file, critical messages and higher ones also go
-# to another host and to the console. Messages to
-# the host finlandia are forwarded in RFC 3164
-# format (using the template defined above).
-#
-kern.* /var/adm/kernel
-kern.crit @finlandia;RFC3164fmt
-kern.crit /dev/console
-kern.info;kern.!err /var/adm/kernel-info
-
-The first rule direct any message that has the kernel facility to the -file /var/adm/kernel.
-
-The second statement directs all kernel messages of the priority crit -and higher to the remote host finlandia. This is useful, because if the -host crashes and the disks get irreparable errors you might not be able -to read the stored messages. If they're on a remote host, too, you -still can try to find out the reason for the crash.
-
-The third rule directs these messages to the actual console, so the -person who works on the machine will get them, too.
-
-The fourth line tells rsyslogd to save all kernel messages that come -with priorities from info up to warning in the file -/var/adm/kernel-info. Everything from err and higher is excluded.
-
-
-# The tcp wrapper loggs with mail.info, we display
-# all the connections on tty12
-#
-mail.=info /dev/tty12
-
-This directs all messages that uses mail.info (in source LOG_MAIL | -LOG_INFO) to /dev/tty12, the 12th console. For example the tcpwrapper -tcpd(8) uses this as it's default.
-
-
-# Store all mail concerning stuff in a file
-#
-mail.*;mail.!=info /var/adm/mail
-
-This pattern matches all messages that come with the mail facility, -except for the info priority. These will be stored in the file -/var/adm/mail.
-
-
-# Log all mail.info and news.info messages to info
-#
-mail,news.=info /var/adm/info
-
-This will extract all messages that come either with mail.info or with -news.info and store them in the file /var/adm/info.
-
-
-# Log info and notice messages to messages file
-#
-*.=info;*.=notice;\
-mail.none /var/log/messages
-
-This lets rsyslogd log all messages that come with either the info or -the notice facility into the file /var/log/messages, except for all
-messages that use the mail facility.
-
-
-# Log info messages to messages file
-#
-*.=info;\
-mail,news.none /var/log/messages
-
-This statement causes rsyslogd to log all messages that come with the -info priority to the file /var/log/messages. But any message coming -either with the mail or the news facility will not be stored.
-
-
-# Emergency messages will be displayed using wall
-#
-*.=emerg *
-
-This rule tells rsyslogd to write all emergency messages to all -currently logged in users. This is the wall action.
-
-
-# Messages of the priority alert will be directed
-# to the operator
-#
-*.alert root,rgerhards
-
-This rule directs all messages with a priority of alert or higher to -the terminals of the operator, i.e. of the users "root'' and -"rgerhards'' if they're logged in.
-
-
-*.* @finlandia
-
-This rule would redirect all messages to a remote host called -finlandia. This is useful especially in a cluster of machines where all -syslog messages will be stored on only one machine.
-
-In the format shown above, UDP is used for transmitting the message. -The destination port is set to the default auf 514. Rsyslog is also -capable of using much more secure and reliable TCP sessions for message -forwarding. Also, the destination port can be specified. To select TCP, -simply add one additional @ in front of the host name (that is, @host -is UPD, @@host is TCP). For example:
-
-
-*.* @@finlandia
-
-To specify the destination port on the remote machine, use a colon -followed by the port number after the machine name. The following -forwards to port 1514 on finlandia:
-
-
-*.* @@finlandia:1514
-
-This syntax works both with TCP and UDP based syslog. However, you will -probably primarily need it for TCP, as there is no well-accepted port -for this transport (it is non-standard). For UDP, you can usually stick -with the default auf 514, but might want to modify it for security rea-
-sons. If you would like to do that, it's quite easy:
-
-
-*.* @finlandia:1514
-
-
-
-*.* >dbhost,dbname,dbuser,dbpassword;dbtemplate
-
-This rule writes all message to the database "dbname" hosted on -"dbhost". The login is done with user "dbuser" and password -"dbpassword". The actual table that is updated is specified within the -template (which contains the insert statement). The template is called -"dbtemplate" in this case.

-

:msg,contains,"error" @errorServer

-

This rule forwards all messages that contain the word "error" -in the msg part to the server "errorServer". Forwarding is via UDP. -Please note the colon in fron

-

CONFIGURATION FILE SYNTAX DIFFERENCES

+

Configuration File Syntax Differences

Rsyslogd uses a slightly different syntax for its configuration file than the original BSD sources. Originally all messages of a specific priority and above were forwarded to the log @@ -1272,4 +68,15 @@ additional features (like template and database support). For obvious reasons, the syntax for defining such features is available in rsyslogd, only.

- + +

[back to top] +[manual index] +[rsyslog site]

+

This documentation is part of the +rsyslog project.
+Copyright © 2008 by Rainer Gerhards and +Adiscon. Released under the GNU GPL +version 2 or higher.

+ + +> -- cgit