While the rsyslogd sources have been heavily modified a couple of notes are in order. First of all there has been a systematic attempt to ensure that rsyslogd follows its default, standard BSD behavior. Of course, some configuration file changes are necessary in order to support the template system. However, rsyslogd should be able to use a standard syslog.conf and act like the original syslogd. However, an original syslogd will not work correctly with a rsyslog-enhanced configuration file. At best, it will generate funny looking file names.
RSYSLOGD(8) Linux System Administration RSYSLOGD(8). Some configuration file changes are necessary in order to support the template system. However, rsyslogd should be able to use a standard syslog.conf and act like the original syslogd. Rsyslogd produces debugging information according to the RSYSLOG_DEBUG environment variable and the. 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. As a consequence, using this template type for text outputs is usually only useful for debugging or very special cases (e.g. Where the text.
The second important concept to note is that this version of rsyslogd interacts transparently with the version of syslog found in the standard libraries. If a binary linked to the standard shared libraries fails to function correctly we would like an example of the anomalous behavior. OPTIONS -A When sending UDP messages, there are potentially multiple paths to the target destination. By default, rsyslogd only sends to the first target it can successfully send to.
If -A is given, messages are sent to all targets. This may improve reliability, but may also cause message duplication. This option should be enabled only if it is fully understood.4 Causes rsyslogd to listen to IPv4 addresses only. If neither -4 nor -6 is given, rsyslogd listens to all configured addresses of the system.6 Causes rsyslogd to listen to IPv6 addresses only.
If neither -4 nor -6 is given, rsyslogd listens to all configured addresses of the system.c version This option has been obsoleted and has no function any longer. It is still accepted in order not to break existing scripts. However, future versions may not support it.D Runs the Bison config parser in debug mode. This may help when hard to find syntax errors are reported.
Please note that the output generated is deeply technical and orignally targeted towards developers.d Turns on debug mode. Using this the daemon will not proceed a to set itself in the background, but opposite to that stay in the foreground and write much debug information on the current tty. See the DEBUGGING section for more information.f config file Specify an alternative configuration file instead of /etc/rsyslog.conf, which is the default.i pid file Specify an alternative pid file instead of the default one. This option must be used if multiple instances of rsyslogd should run on a single machine.l hostlist Specify a hostname that should be logged only with its simple hostname and not the fqdn. Multiple hosts may be specified using the colon (``:') separator.n Avoid auto-backgrounding.
This is needed especially if the rsyslogd is started and controlled.N level Do a coNfig check. Do NOT run in regular mode, just check configuration file correctness. This option is meant to verify a config file. To do so, run rsyslogd interactively in foreground, specifying -f and -N level. The level argument modifies behaviour. Currently, 0 is the same as not specifying the -N option at all (so this makes limited sense) and 1 actually activates the code.
Later, higher levels will mean more verbosity (this is a forward-compatibility option). Rsyslogd is started and controlled.q add hostname if DNS fails during ACL processing During ACL processing, hostnames are resolved to IP addresses for performance reasons. If DNS fails during that process, the hostname is added as wildcard text, which results in proper, but somewhat slower operation once DNS is up again.Q do not resolve hostnames during ACL processing Do not resolve hostnames to IP addresses during ACL processing.s domainlist Specify a domainname that should be stripped off before logging. Multiple domains may be specified using the colon (``:') separator. Please be advised that no sub-domains may be specified but only entire domains. For example if -s north.de is specified and the host logging resolves to satu.infodrom.north.de no domain would be cut, you will have to specify two domains like: -s north.de:infodrom.north.de.S ipaddress local client source IP rsyslogd uses ipaddress as local client address while connecting to remote logserver. Currently used by omrelp only and only with tcp.u userlevel This is a 'catch all' option for some very seldomly-used user settings.
The 'userlevel' variable selects multiple things. Add the specific values to get the combined effect of them. A value of 1 prevents rsyslogd from parsing hostnames and tags inside messages. A value of 2 prevents rsyslogd from changing to the root directory. This is almost never a good idea in production use. This option was introduced in support of the internal testbed.
To combine these two features, use a userlevel of 3 (1+2). Whenever you use an -u option, make sure you really understand what you do and why you do it.v Print version and exit.w Suppress warnings issued when messages are received from non-authorized machines (those, that are in no AllowedSender list).x Disable DNS for remote messages. SIGNALS Rsyslogd reacts to a set of signals. You may easily send a signal to rsyslogd using the following: kill -SIGNAL $(cat /var/run/rsyslogd.pid). Note that -SIGNAL must be replaced with the actual signal you are trying to send, e.g. So it then becomes: kill -HUP $(cat /var/run/rsyslogd.pid) HUP This lets rsyslogd perform close all open files. TERM, INT, QUIT Rsyslogd will die.
USR1 Switch debugging on/off. This option can only be used if rsyslogd is started with the -d debug option. CHLD Wait for childs if some were born, because of wall'ing messages.
SECURITY THREATS There is the potential for the rsyslogd daemon to be used as a conduit for a denial of service attack. A rogue program(mer) could very easily flood the rsyslogd daemon with syslog messages resulting in the log files consuming all the remaining space on the filesystem. Activating logging over the inet domain sockets will of course expose a system to risks outside of programs or individuals on the local machine. There are a number of methods of protecting a machine: 1. Implement kernel firewalling to limit which hosts or networks have access to the 514/UDP socket. Logging can be directed to an isolated or non-root filesystem which, if filled, will not impair the machine.
The ext2 filesystem can be used which can be configured to limit a certain percentage of a filesystem to usage by root only. NOTE that this will require rsyslogd to be run as a non-root process. ALSO NOTE that this will prevent usage of remote logging on the default port since rsyslogd will be unable to bind to the 514/UDP socket.
Disabling inet domain sockets will limit risk to the local machine. Message replay and spoofing If remote logging is enabled, messages can easily be spoofed and replayed. As the messages are transmitted in clear-text, an attacker might use the information obtained from the packets for malicious things. Also, an attacker might replay recorded messages or spoof a sender's IP address, which could lead to a wrong perception of system activity. These can be prevented by using GSS-API authentication and encryption. Be sure to think about syslog network security before enabling it.
DEBUGGING When debugging is turned on using -d option then rsyslogd will be very verbose by writing much of what it does on stdout. FILES /etc/rsyslog.conf Configuration file for rsyslogd. See for exact information. /dev/log The Unix domain socket to from where local syslog messages are read. /var/run/rsyslogd.pid The file containing the process id of rsyslogd. Prefix/lib/rsyslog Default directory for rsyslogd modules. The prefix is specified during compilation (e.g.
ENVIRONMENT RSYSLOGDEBUG Controls runtime debug support.It contains an option string with the following options possible (all are case insensitive). LogFuncFlow Print out the logical flow of functions (entering and exiting them) FileTrace Specifies which files to trace LogFuncFlow. If not set (the default), a LogFuncFlow trace is provided for all files. Set to limit it to the files specified.FileTrace may be specified multiple times, one file each (e.g.
Export RSYSLOGDEBUG='LogFuncFlow FileTrace=vm.c FileTrace=expr.c' PrintFuncDB Print the content of the debug function database whenever debug information is printed (e.g. PrintAllDebugInfoOnExit Print all debug information immediately before rsyslogd exits (currently not implemented!) PrintMutexAction Print mutex action as it happens. Useful for finding deadlocks and such. NoLogTimeStamp Do not prefix log lines with a timestamp (default is to do that).
NoStdOut Do not emit debug messages to stdout. If RSYSLOGDEBUGLOG is not set, this means no messages will be displayed at all. Help Display a very short list of commands - hopefully a life saver if you can't access the documentation.
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RSYSLOGDEBUGLOG If set, writes (almost) all debug message to the specified log file in addition to stdout. RSYSLOGMODDIR Provides the default directory in which loadable modules reside. BUGS Please review the file BUGS for up-to-date information on known bugs and annoyances.
Further Information Please visit for additional information, tutorials and a support forum. SEE ALSO, COLLABORATORS rsyslogd is derived from sysklogd sources, which in turn was taken from the BSD sources.
Special thanks to Greg Wettstein ([email protected]) and Martin Schulze ([email protected]) for the fine sysklogd package.
Why are you logging data? Two reasons come to my mind specifically: statistics and debug information. In the first case not being able to access your data for a period of time is not that big of a deal, statistics are only significant if you can collect them over a long timeframe.
But if a specific server has an all out breakdown, and one service after another crashes, you want to determine what is happening right now. But then you'd have to have access to your logs over ssh. And this service has just crashed too.
Once again we can count on our OS for offering a solution to this problem. Starting in 2004 Rainer Gerhards started writing, a logging daemon which offers remote logging and strong filtering capacities.
This article will cover setting up the system for remote logging and show some examples of possible day to day use. I will include the standard syslogs as well as apache's access and error logs Disclaimer Be careful if you start changing your logging setup. Backup relevant data and check if your new setup still functions properly afterwards. This article is just an introduction, not a faultless reference. If you don't know what something means or does, look it up please.
Backups of configuration files might come in handy too. If I made a mistake and you found out, please inform me as well. Logging on linux: a small and very incomplete history Back in the days, when was still seen as a masterpiece of special effects, created a logging standard for sendmail. This standard soon was adopted by other programs and became the de facto logging standard for unix systems. A small 20 years later syslog-ng, an open source implementation of syslog, emerged.
This brought huge improvements in the fields of filtering and configuration. Finally almost in present times (2004) Aforementioned Rainer Gerhards started writing rsyslog as a competitor for syslog-ng because he thought a competitor was. Getting started Now this is easy, we're on linux after all. Aptitude install rsyslog should be enough. What you could do is check if there are other logging daemons running on your system (or maybe you already have rsyslog running).
You might run into sysklogd and others. You'll not be needing them as we're going to start remote logging. If you check de rsyslog.conf file in /etc you'll see that is set up for local logging at the moment. For now remove every rule from the file and add only one line:.
@1.2.3.4:514 If you now restart rsyslog every will be send to a server with ip 1.2.3.4 over. By adding a second @ in front of the first and changing your port you can send using but I don't mind a log getting lost every now and then so UDP will do just fine. The. may be a bit much. If you know that all you are going to do with specific logs is drop them on the receiving server you might as well drop them on sending servers and spare the bandwidth. Read onwards to see how.
That is all for syslog purposes, but we still need to get Apache to also use syslog instead of listening to its own commands. For the error log this is quite simple, we can tell it to use syslog and be finished with it. For the access logs things lie a little different. I disabled other logging rules in our apache setup and put the following rules in /etc/apache2/conf.d/logging.conf (The filename is free to choose, the location isn't): CustomLog ' /usr/bin/logger -t apache -i -p local6.notice' procurios-syslog error log syslog As you can see error log isn't that big of a deal, but for the access logs we need to have CustomLog do something peculiar. Every access log is piped to /usr/bin/logger which results in the log getting received by rsyslog. As you can see the facility (local6) and priority (notice) are also passed along. Finally a specific log format is chosen (procurios-syslog: in this case defined somewhere else in the same file).
So every server is sending syslogs, apache error logs and apache access logs to 1.2.3.4, the only problem is: at 1.2.3.4 no one is listening. Setting up the host To get 1.2.3.4 to listen we need to change its rsyslog.conf file as well. Below is what is needed to listen for UDP on port 514 (there should be a bunch of other stuff in your file, if you installed rsyslog via aptitude it should be there and you only have to uncomment the UDP part). $ModLoad imudp $UDPServerAddress 1.2.3.4 $UDPServerRun 514 The configuration above results in exactly three things:. A module is loaded, making our rsyslog set up and capable of listening for UDP packages.
An ip address is defined, if this is left out or a. is used all ips this server knows are listened to. In general you probably don't want this, in our case the machine only listens to its local ip, meaning there can be no outside flooding. The port where rsyslog needs to be listening is defined. If you restart rsyslog you can then check if your configuration worked. Using the command netstat -nlp you should get a result which looks like this: udp 0 0 1.2.3.4:514 0.0.0.0:. 16637/rsyslogd Storing the incoming logs So every log from every server is now received at 1.2.3.4.
If you want them al in one file all you'll need to do is add a single rule to your rsyslog.conf and restart it:. /var/log/oneGiantHeapOfLogs.log As this is probably exactly what you don't want we'll need some filters. But before we do that I'll need to introduce you to another concept called templates. Templates Since a lot of servers are sending logs to one machine it won't do to simply filter out local6.notice to /var/log/apache-access.log. You'll want the access logs per server at least! The same goes for other stuff so we'll need a way to dynamically put logs of the same facility into different files. For this purpose are used.
Below are some examples of what we use: $template syslog,'/var/log/external/%fromhost%/syslog.log' $template apacheError,'/var/log/external/%fromhost%/apache/error.log' $template apacheAccess,'/var/log/external/%fromhost%/apache/%msg:R,ERE,1,ZERO:imp:(a-zA-Z0-9 -+).-end%-access.log' $template mailError, '/var/log/external/%fromhost%/mail/error.log' There are two things happening here. First of all you'll notice%fromhost%. This is a placeholder which is dynamically replaced with the DNS-resolved hostname of the machine the current log came from. Other options to use are found. The second placeholder (%msg.) a bit more obscure but in the end it is nothing more than a regular expression.
Since our servers host multiple implementations it is very convenient to have access logs per implementation. For this we put some information in the LogFormat on the sending machines which is parsed out here.
To see the syntax of regular expressions in templates please read again, but scroll below the property replacers. Actual filtering Since we have templates resulting in dynamic filenames now we can start the actual filtering. First we filter out apaches logs: local7.?apacheError & local6.notice?apacheAccess & I'll explain what these lines accomplish.
Apache uses local7 to send error logs and we told apache to use local6.notice for access logs, all we do now is put them in their dynamic files. The question mark is necessary to have rsyslog know a template is following.
If an error log is coming from v004 it will be put into /var/log/external/v004/apache/error.log if it comes from v027 it will be stored in /var/log/external/v027/apache/error.log. On the next line (which seems to be necessary in this case) there are an ampersand and a tilde. The tilde tells rsyslog to drop all logs that were filtered out by the preceding command, the ampersand is merely used to connect the two lines. Since our mailservers are logging remotely too, it would be nice if we get mail related errors in a specific file as well. But I'm only interested in errors from actual mailservers, I don't need specific logs for a postfix on a random virtual machine. This proved to be a little more tricky and I don't know if it is the ideal solution but it is working for me: if $syslogfacility-text 'mail' and $syslogseverity-text 'info' and $fromhost startswith 'mail' then?mailInfo & The if-and-then construction can use the same property replacers introduced earlier and can also work with a number of predefined compare operations (isequal, startswith and ). If all conditions are met the log is put into another dynamic file and it is dropped afterwards.
Please note that everything up to & must be on a single line. The breaks are there for reading purposes only. Now our apache access and error logs are stored in seperate files as well as the error logs from our mailservers. All we want now is the rest of our logs in the syslog file:.?syslog This is the last filter in the file so all that wasn't catched by earlier filters ends up in the syslog file.
Wrap up The configuration lines above are snippets from our actual configuration, not all is present there. If you want to setup remote logging yourself, take care to keep thinking and take your own situation into account. Having said that I hope this article will be of use when you decide to start logging remote! Comments. gauravb Wrote on Hi, I am able to forward the messages from the rsyslog server to central syslog server with the debug mode and once the debug mode is disabled the rsyslog doesn't send the messages to the central syslog server and it also doesn't storage the incoming messages anywhere withthin the server.
I am using spoofing, to make sure the source IP is not changed while forwarding the message to the central server. Any idea why this happens? Regards. Erik Wrote on What does it mean: Apache 'uses' local7 to send error logs? What is 'local7' and where can I find that Apache uses it?. Freek Lijten Wrote on @gauravb, I can't really say to be honest. It can be all kind of things in your setup:( @Erik local7 (and others) are part of the syslog environment, see the part on facility levels here: Apache uses local7 by default as specified here: (search for local7 in that paragraphs).
Wrote on I trying to get my webserver log send to prtg server, but when i add the configuration it show me the following error. root@colibri # /etc/init.d/httpd restart Stopping httpd: FAILED Starting httpd: Syntax error on line 2 of /etc/httpd/conf.d/logging.conf: Invalid command 'error', perhaps misspelled or defined by a module not included in the server configuration FYI, i am running CentOS 6.2 httpd-tools-2.2.15-15.el6.centos.1.x8664 rsyslog-5.8.10-6.el6.x8664 it seem that i neet to enable some kind module in httpd/apache. Any suggestion will be appreciated.
Aneesh Wrote on Hi, This is sles11 OS and it is not listening syslog server IP 10.250.1.230 and udp port 514. Could you please advice why it is listening. Slestest: # grep -i udp /etc/rsyslog.conf $ModLoad imudp $UDPServerAddress 10.250.1.230 $UDPServerRun 514 slestest: # tail -2 /etc/rsyslog.conf. @10.250.1.230:514 # slestest: # netstat -nlp grep -i syslog udp 0 0 0.0.0.0:37420 0.0.0.0:.
19276/rsyslogd slestest: # lsof -i:37420 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME rsyslogd 19276 root 21u IPv4 23473806 0t0 UDP.:37420 Thanks Aneesh. Varun Wrote on Hello, I have configured rsyslog and set following value $template serverlog, '/var/log/TEST/%HOSTNAME%/server.log' local4.?serverlog Now the code will create folder based on%HOSTNAME%, but I would like to create folder First on server name(company name) and then HOSTNAME. For example: I am having 3 server for the 2 different company ABCD and xyz, and their 3 server names (hostname) are. Abcdapp-1t abcdapp-2t abcdapp-3t xyzapp-1t xyzapp-2t xyzapp-3t Now if i run the above template it will create different folder according to host name under /var/log/TEST folder, but I need to create 2 different folders ABCD and XYZ and relative hostname will go under specific directory and create subfolder.
For example: required to looks like this. /var/log/TEST/ABCD/abcdapp-1t/server.log /var/log/TEST/ABCD/abcdapp-2t/server.log /var/log/TEST/ABCD/abcdapp-3t/server.log /var/log/TEST/XYZ/xyzapp-1t/server.log /var/log/TEST/XYZ/xyzapp-2t/server.log /var/log/TEST/XYZ/xyzapp-3t/server.log As i have more then 15 different server of clients i can not do it in one statement. How can i use If else IF statements in rsyslog, so I can filter by HOSTNAME and move to specific folder. Is there any suggestion?
Please advice. Thanks, Varun. Italic and bold.This is italic., and so is this.This is bold., and so is this. Links This is a link to Procurios(Lists A bulleted list can be made with: - Minus-signs, + Add-signs,. Or an asterisk. A numbered list can be made with: 1.
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