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| author | Rainer Gerhards <rgerhards@adiscon.com> | 2008-11-18 11:40:23 +0100 |
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| committer | Rainer Gerhards <rgerhards@adiscon.com> | 2008-11-18 11:40:23 +0100 |
| commit | a5417f16044d7d56dbceeea09e25ba3e8c47cc01 (patch) | |
| tree | de086d9f0baa496f3743b39e4c49b05edab1a303 /doc/rsyslog_conf_actions.html | |
| parent | ba201a941435bc5fec2c333155e1a8e16c4a9c05 (diff) | |
| parent | 704a1145d64532df36624a3c9850b0c86f38f76f (diff) | |
| download | rsyslog-a5417f16044d7d56dbceeea09e25ba3e8c47cc01.tar.gz rsyslog-a5417f16044d7d56dbceeea09e25ba3e8c47cc01.tar.xz rsyslog-a5417f16044d7d56dbceeea09e25ba3e8c47cc01.zip | |
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diff --git a/doc/rsyslog_conf_actions.html b/doc/rsyslog_conf_actions.html new file mode 100644 index 00000000..2ef3f4b0 --- /dev/null +++ b/doc/rsyslog_conf_actions.html @@ -0,0 +1,336 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html><head><title>Actions - rsyslog.conf</title></head> +<body> +<p>This is a part of the rsyslog.conf documentation.</p> +<a href="rsyslog_conf.html">back</a> +<h2>Actions</h2> +<p>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.<br> +<br> +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.<br> +<br> +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.</p> +<p><b>You can have multiple actions for a single selector </b> (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</p> +<p><code><b>*.=crit rger<br> +& root<br> +& /var/log/critmsgs</b></code></p> +<p>These three lines send critical messages to the user rger and +root and also store them in /var/log/critmsgs. <b>Using multiple +actions per selector is</b> convenient and also <b>offers +a performance benefit</b>. 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:</p> +<p><code><b>*.=crit rger<br> +*.=crit root<br> +*.=crit /var/log/critmsgs</b></code></p> +<p> </p> +<h3>Regular File</h3> +<p>Typically messages are logged to real files. The file has to +be specified with full pathname, beginning with a slash "/''.<br> +<br> +<br> +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.</p> +<p>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. </p> +<p><b>The filename can be either static </b>(always +the same) or <b>dynamic</b> (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. </p> +<p>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:</p> +<blockquote> +<code>*.* ?DynFile</code> +</blockquote> +<p>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</p> +<blockquote> +<code>*.* -?DynFile</code></blockquote> +<p>And of course you can use templates to specify the output +format:</p> +<blockquote> +<code>*.* ?DynFile;MyTemplate</code></blockquote> +<p><b>A word of caution:</b> rsyslog creates files as +needed. So if a new host is using your syslog server, rsyslog will +automatically create a new file for it.</p> +<p><b>Creating directories is also supported</b>. For +example you can use the hostname as directory and the program name as +file name:</p> +<blockquote> +<code>$template DynFile,"/var/log/%HOSTNAME%/%programname%.log"</code></blockquote> +<h3>Named Pipes</h3> +<p>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.</p> +<h3>Terminal and Console</h3> +<p>If the file you specified is a tty, special tty-handling is +done, same with /dev/console.</p> +<h3>Remote Machine</h3> +<p>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<br> +administration needs.<br> +<br> +<b>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.</b></p> +<p>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:</p> +<table id="table2" border="1" width="100%"> +<tbody> +<tr> +<td> +<p align="center"><b>z<number></b></p> +</td> +<td>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. +<p><b>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.</b></p> +<p>Compressed messages are automatically detected and +decompressed by the receiver. There is nothing that needs to be +configured on the receiver side.</p> +</td> +</tr> +<tr> +<td> +<p align="center"><b>o</b></p> +</td> +<td><b>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.</b> +<p>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...).</p> +<p>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...</p> +</td> +</tr> +</tbody> +</table> +<p><br> +The hostname may be followed by a colon and the destination port.</p> +<p>The following is an example selector line with forwarding:</p> +<p>*.* @@(o,z9)192.168.0.1:1470</p> +<p>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.</p> +<p>*.* @192.168.0.1</p> +<p>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.</p> +<p>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. +<p>A valid sample to send messages to the IPv6 host 2001::1 at port 515 +is as follows: +<p>*.* @[2001::1]:515 +<p>This works with TCP, too. +<p><b>Note to sysklogd users:</b> sysklogd does <b>not</b> +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:</p> +<p class="MsoPlainText">$template +sysklogd,"<%PRI%>%TIMESTAMP% %syslogtag%%msg%\""<br> +*.* @192.168.0.1;sysklogd</p> +<h3>List of Users</h3> +<p>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.</p> +<h3>Everyone logged on</h3> +<p>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 ("*'').</p> +<h3>Call Plugin</h3> +<p>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:</p> +<p>:modname:params;template</p> +<p>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.</p> +<p>As an example, the ommysql module may be called as follows:</p> +<p>:ommysql:dbhost,dbname,dbuser,dbpassword;dbtemplate</p> +<p>For details, please see the "Database Table" section of this +documentation.</p> +<p>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.</p> +<h3>Database Table</h3> +<p>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 <a href="http://www.monitorware.com/">MonitorWare</a>-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<br> +use any other schema of your liking - you just need to define a proper +template and assign this template to the action.<br> +<br> +The database writer is called by specifying a greater-then sign +(">") in front of the database connect information. Immediately +after that<br> +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:<br> +<br> +>dbhost,dbname,dbuser,dbpassword;dbtemplate</p> +<p><b>Important: to use the database functionality, the +MySQL output module must be loaded in the config file</b> BEFORE +the first database table action is used. This is done by placing the</p> +<p><code><b>$ModLoad ommysql</b></code></p> +<p>directive some place above the first use of the database write +(we recommend doing at the the beginning of the config file).</p> +<h3>Discard</h3> +<p>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.</p> +<p>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.</p> +<p>Discard is just the single tilde character with no further +parameters:</p> +<p>~</p> +<p>For example,</p> +<p>*.* ~</p> +<p>discards everything (ok, you can achive the same by not +running rsyslogd at all...).</p> +<h3>Output Channel</h3> +<p>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.</p> +<h3>Shell Execute</h3> +<p>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.</p> +<p>^program-to-execute;template</p> +<p>The program-to-execute can be any valid executable. It +receives the template string as a single parameter (argv[1]).</p> +<p><b>WARNING:</b> 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.</p> +<h3>Template Name</h3> +<p>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.</p> + + +<p>[<a href="manual.html">manual index</a>] +[<a href="rsyslog_conf.html">rsyslog.conf</a>] +[<a href="http://www.rsyslog.com/">rsyslog site</a>]</p> +<p><font size="2">This documentation is part of the +<a href="http://www.rsyslog.com/">rsyslog</a> project.<br> +Copyright © 2008 by <a href="http://www.gerhards.net/rainer">Rainer Gerhards</a> and +<a href="http://www.adiscon.com/">Adiscon</a>. Released under the GNU GPL +version 2 or higher.</font></p> +</body> +</html> + |