syslog-ng for collecting remote logs


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  1. #1
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    syslog-ng for collecting remote logs

    Syslog-ng Configuration

    This is a breakdown of what the syslog-ng.conf file looks like and what it does. I never found a guide like this, so I thought I would post one.

    Syslog-ng takes system logging to the next level. The “normal” syslog daemon leaves a lot to be desired especially in collecting logs from remote servers.

    Syslogd (the original one) does not separate logs into different files, just collects the logs and dumps them all together, which is good sometimes, but mostly bad.

    So here we go:
    As with all good config files this one begins with comments (starting with #) describing the files purpose:

    (NOTE: the actual conf file is all bold in this doc for easy reference. Also in code tags, so the indentation gets preserved -- bwkaz )

    Code:
    # Begin /etc/syslog-ng/syslog-ng.conf
    # Taken from Syslog-ng configuration for Linux from Scratch
    # Re-authored by MLeo
    # Date:  February 2006
    # Version 2 (my own version number)
    
    Now, as with most linux apps, there are global options to define:

    Code:
    options { 	sync (0);
    		time_reopen (10);
    		log_fifo_size (1000);
    		long_hostnames(off);
    # this next one is important as it will build folders based on the remote servers name:
    		use_dns (yes);	
    		use_fqdn (no);
    # this will automatically build the folder structure for incoming logs:
    		create_dirs (yes);
    		keep_hostname (yes);
    };
    There are 4 major sections (besides the above) that make up this file:

    Source : this basically tells syslog-ng what to listen too.
    Destination : this defines the files to send the logs too
    filter : defines how to break the incoming logs into individual reporting services
    log : the log section brings the source, destination and filters together to actually begin the logging.



    the first source is defined as “src” but can be named anything from what I have found

    Code:
    # the unix-stream seems to be just the regular mechanism
    # linux uses to log from services running locally 
    source src {	unix-stream("/dev/log");
    		internal();
    		pipe("/proc/kmsg");
        };
    
    # here we define 2 additional source's (remotetcp and remoteudp)
    # to receive logs from remote machines.  By default, syslog sends logs via UDP
    # and syslog-ng uses TCP, so we define both so we can receive log's from
    # either type of clients.  Again, the name's are whatever you define
    # them as:
    
    source remotetcp { tcp(ip(0.0.0.0) port(514)); };
    source remoteudp { udp(); };
    Now that we have determined what to listen too, lets target where we want the logs to go.

    As you will see, syslog-ng can use system variables ($HOST, $DATE, etc) which makes it incredibly customizable.

    One thing to consider, however, is that if you are troubleshooting an issue across many systems, you would have to look at several different logs if you were to parse all the logs into their own directories. If you dump all logs into one giant file, it would be easy to sort by time, then see a common thread across all your systems. However, that file could become huge and unwieldy after a while.

    The format should be obvious, and you can make the destinations where ever you want.
    In our example we are only separating the auth and authpriv logs into their own directories
    in /var/log/, but all other logs just dump into their respective paths.
    You do not have to create these folders before hand as the global setting will allow this to
    happen on the fly.

    Code:
    # The name (authpriv, auth, syslog, etc) is up to you.  These do not have to match the
    # facility you are trying to log from (or too), but it just makes sense to name them the
    # same.
    
    destination authpriv { file("/var/log/$HOST/authorize.log"); };
    destination auth     { file("/var/log/$HOST/authorize.log"); };
    destination syslog { file("/var/log/syslog.log"); };
    destination cron { file("/var/log/cron.log"); };
    destination daemon { file("/var/log/daemon.log"); };
    destination kernel { file("/var/log/kernel.log"); };
    destination lpr { file("/var/log/lpr.log"); };
    destination user { file("/var/log/user.log"); };
    destination uucp { file("/var/log/uucp.log"); };
    destination mail { file("/var/log/mail.log"); };
    destination news { file("/var/log/news.log"); };
    destination debug { file("/var/log/debug.log"); };
    destination messages { file("/var/log/$HOST/messages.log"); };
    destination everything { file("/var/log/everything.log"); };
    destination console { usertty("root"); };
    destination console_all { file("/dev/tty12"); };
    The filter section is where we define what daemon/process/facility we want to log from.
    The names (f_auth, f_cron, f_kernel) can be named what ever you like. The facility, however, must be the actual process from where the logs are coming from.

    Code:
    # Nothing special here, just like source and destination, name them what you want.
    filter f_auth { facility(auth); };
    filter f_authpriv { facility(auth, authpriv); };
    filter f_syslog { not facility(authpriv, mail); };
    filter f_cron { facility(cron); };
    filter f_daemon { facility(daemon); };
    filter f_kernel { facility(kern); };
    filter f_lpr { facility(lpr); };
    filter f_mail { facility(mail); };
    filter f_news { facility(news); };
    filter f_user { facility(user); };
    filter f_uucp { facility(cron); };
    filter f_news { facility(news); };
    filter f_debug { not facility(auth, authpriv, news, mail); };
    filter f_messages { level(info..warn) and not facility(auth, authpriv, mail, news); };
    filter f_everything { level(debug..emerg) and not facility(auth, authpriv); };
    filter f_emergency { level(emerg); };
    filter f_info { level(info); };
    filter f_notice { level(notice); };
    filter f_warn { level(warn); };
    filter f_crit { level(crit); };
    filter f_err { level(err); };
    Now, onto the actual execution of the syslog-ng process.

    In the above sections, we have simply defined many variables, and in this section we will execute on them:


    The format is simple:

    log { source(yoursourcehere); filter(yourfilterhere); destination(yourdestinationhere);

    Simple, huh?

    The log process then parses out and piece's together the different variables and starts logging the information.

    As clients connect, syslog-ng will build the directory structure on the fly for you if you have defined $HOST above.

    Code:
    log { source(src); filter(f_authpriv); destination(authpriv); };
    log { source(remotetcp); filter(f_authpriv); destination(authpriv); };
    log { source(remotetcp); filter(f_auth); destination(auth); };
    log { source(remoteudp); filter(f_authpriv); destination(authpriv); };
    log { source(remoteudp); filter(f_auth); destination(auth); };
    log { source(remoteudp); filter(f_messages); destination(messages); };
    log { source(src); filter(f_syslog); destination(syslog); };
    log { source(src); filter(f_cron); destination(cron); };
    log { source(src); filter(f_daemon); destination(daemon); };
    log { source(src); filter(f_kernel); destination(kernel); };
    log { source(src); filter(f_lpr); destination(lpr); };
    log { source(src); filter(f_mail); destination(mail); };
    log { source(src); filter(f_news); destination(news); };
    log { source(src); filter(f_user); destination(user); };
    log { source(src); filter(f_uucp); destination(uucp); };
    log { source(src); filter(f_debug); destination(debug); };
    log { source(src); filter(f_messages); destination(messages); };
    log { source(src); filter(f_emergency); destination(console); };
    log { source(src); filter(f_everything); destination(everything); };
    log { source(src); destination(console_all); };
    
    # END /etc/syslog-ng/syslog-ng.conf
    A few things to remember:

    Its a good idea to shutoff syslogd permanently since we don't want to get confused later on.

    Also, make sure you set syslog-ng to start on boot for you particular distro.

    Finally, lets look at a simple client config to send its log files to our central log server:
    To add the ability to any syslog client to send its logs to a remote server, simply add a line including what to log and instead of listing a local file, list @remotelogserver.

    Of course, it is a good idea to also log files locally, but you can have your syslog log the same message to multiple places.

    This is just the modified piece of the client config file:

    Code:
    authpriv.*                                                  /var/log/secure
    auth.*;authpriv.*                                       @yourremote.log.server
    As you see, the authpriv logs to /var/log/secure, but also sends it's info to yourremote.log.server as well.

    However, when it arrives at yourremote.log.server, it adheres to its path for logging. In our case:

    log { source(remoteudp); filter(f_authpriv); destination(authpriv); };

    which will show up in /var/log/$HOST/authorize.log on our log server.

    get it?


    Disclaimer: I am no expert on this. I just happened to get this to work after a few hours of tweaks. Some things might work if configured differently. For instance:

    source remotetcp { tcp(ip() port(514)); };
    Might work just as well as:
    source remotetcp { tcp(ip(0.0.0.0) port(514)); };

    I just haven't gone back to test each line of changes I had to make to get this to work.

    I was just at a loss for a break down of the file so I thought I'd share what I had found.
    Last edited by bwkaz; 02-10-2006 at 10:41 AM. Reason: Added code tags to preserve indentation
    m1ke_l
    Lenovo x120e (gave my wife the Asus 1015N)http://justlinux.com/forum/showthrea...hreadid=153955
    Fedora 16 (but I haven't settled yet)
    8gigs of RAM (in a NETBOOK!!)
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  2. #2
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    Hey, that's better. Now I can see the line-breaks at resolutions other than 1280x1024, and all the whitespace is also preserved. Much better.

    (Side note: Thanks for explaining a lot of that. I'll probably use syslog-ng on my next machine build, and it's nice to have a reference for when I do decide to move to it.)

    (Second side note: "the unix-stream seems to be just the regular mechanism linux uses to log from services running locally" -- this is almost true. The unix-stream of /dev/log is the regular mechanism that Linux uses to log from services running locally. /dev/log is a "Unix-domain socket" (i.e. it acts just like a network socket, except it has a filename) that the C syslog() function connects to and sends its messages over. syslog-ng connects to the socket too, and receives these messages just like ones it would receive from other hosts -- actually syslogd does the same thing. The term unix-stream just means "Unix-domain socket", i.e. "named socket"; its argument is the socket's name.)

  3. #3
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    thanks bwkaz!!

    I learned how to block out my code after this post so you shouldn't have to clean up after me any more!
    m1ke_l
    Lenovo x120e (gave my wife the Asus 1015N)http://justlinux.com/forum/showthrea...hreadid=153955
    Fedora 16 (but I haven't settled yet)
    8gigs of RAM (in a NETBOOK!!)
    Boston, MA USA/Wondering

    My dad's website (he'll love the traffic) http://www.cafephotos.net/

  4. #4
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    We only use Syslog-ng where I work. We have a lot of servers that "log offsite" to a syslog analyzer so the logs can be sorted, stored, and alerts can be generated, etc. After using syslog-ng at work, I decided I couldn't live without it and set it up at home. It's really the best syslog tool I've worked with.

    It should be noted that building syslog-ng requires libol which is available from the same people who write syslog-ng here. I've built libol and syslog-ng on x86 and x86-64 (both AMD and EM64T) with no problems what-so ever. It is intresting that libol is available under the GPL and not the LGPL....
    "There's a big difference between "copy" and "use". It's exatcly the same
    issue whether it's music or code. You can't re-distribute other peoples
    music (becuase it's _their_ copyright), but they shouldn't put limits on
    how you personally _use_ it (because it's _your_ life)."

    --Linus Torvalds

  5. #5
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    I also remember that the libol install files were packaged in the syslog-ng tar file, so it wasn't a seperate download, but only a seperate install.
    m1ke_l
    Lenovo x120e (gave my wife the Asus 1015N)http://justlinux.com/forum/showthrea...hreadid=153955
    Fedora 16 (but I haven't settled yet)
    8gigs of RAM (in a NETBOOK!!)
    Boston, MA USA/Wondering

    My dad's website (he'll love the traffic) http://www.cafephotos.net/

  6. #6
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    First off, I really appreciate how you broke down syslog-ng's formatting. Much appreciated. One thing I've been pondering is how to separate syslog data by the hosts that are sending the syslog messages to the syslog server. Instead of everything going to /var/log/messages, could I tell syslog-ng.conf to send syslog messages from "host1" to 192.168.1.1:/var/log/host1 or some derivation thereof? Anyone test this before? I tried using this exact format substituting my IP, IP address and file path, of course, but to no avail.
    FC5 serially managed.

  7. #7
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    yes....the variables for the "destination" include things like /var/log/$HOST/messages, etc.
    m1ke_l
    Lenovo x120e (gave my wife the Asus 1015N)http://justlinux.com/forum/showthrea...hreadid=153955
    Fedora 16 (but I haven't settled yet)
    8gigs of RAM (in a NETBOOK!!)
    Boston, MA USA/Wondering

    My dad's website (he'll love the traffic) http://www.cafephotos.net/

  8. #8
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    How would you phrase that specific action in the syslog-ng.conf file? Could you please provide a sample conf file that shows syslog data from two-three different hosts being sent to one central syslog server, but the data goes to two different locations on the syslog server?
    FC5 serially managed.

  9. #9
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    Its been a while since I've set this up but look at the destination line:

    destination auth { file("/var/log/$HOST/authorize.log"); };


    This defines that anything coming from the "auth" function from a remote host will end up in a file /var/log/"remote host"/authorize.log.
    m1ke_l
    Lenovo x120e (gave my wife the Asus 1015N)http://justlinux.com/forum/showthrea...hreadid=153955
    Fedora 16 (but I haven't settled yet)
    8gigs of RAM (in a NETBOOK!!)
    Boston, MA USA/Wondering

    My dad's website (he'll love the traffic) http://www.cafephotos.net/

  10. #10
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    Increasing the power of syslog-ng

    SEC:
    http://www.estpak.ee/%7Eristo/sec/
    But now lets go one step further and send all the incoming logs through a SEC filter, and react to them as they happen, rather then parsing the files after they've been written.

    The code for syslog-ng.conf to use SEC is simple.

    Like the previous setup, we need a destination (d_sec), an input (“net”) and then to start logging it. There is no filter in this instance since we want EVERYTHING to run through the destination(sec.pl).

    Code:
    # SEC destination for emailing alerts to unix_adm
    destination d_sec {
    
    	program("/usr/bin/sec.pl -input=\"-\" -conf=/etc/sec.d/sec.ignores -conf=/etc/sec.d/sec.rules");
    };
    
    # send all logs through sec to filter on rules and email if needed
    log {
    	source(net);
    	destination(d_sec);
    };

    As you can see, syslog-ng calls sec.pl and sec's conf files located in /etc/sec.d/, which we will get to next.

    Installing SEC is really just a matter of extracting the perl script into a path...in our example, /usr/bin/sec.pl, while the configuration files will live in /etc/sec.d/.

    You can either chose a single, large conf file, or several small ones. And you can either point to each file manually, or just tell SEC to look in a directory for anything it can interpret.

    For the example, we will have 2 rules files, one for things we want to react to, and one full of things to ignore. As you get more and more logs coming in, your ignore rules will grow accordingly. The sec.rules file are mostly things you know you want to know about, so they stay pretty static, but can also grow as you learn.

    Here is a sample sec.ignores file (which can be named anything. If you are pointing to a whole directory full of rules files, you should number them so that ignores are read BEFORE regular rules are read in. If you don't, SEC will react to something before it knows to ignore it).

    (See http://kodu.neti.ee/~risto/sec/ for details on each option)

    Note: all the "patterns" are pulled directly from the logs that I know I want to ignore.

    Code:
    # This is the ignores file for SEC
    # This is used via syslog-ng 
    # Company name
    # Author:  Me
    # July 3rd, 2007
    #
    #
    ##########
    # This file is used to set ignore rules
    # i.e.  dba file systems we don't care about, erroneous errors, etc
    #
    
    # ignore /u01 filesystem on server1
    type=Suppress
    ptype=RegExp
    pattern=server1 .*/u01
    
    # patches caused this to start showing up, but mail still sends - need to #investigate
    type=Suppress
    ptype=RegExp
    pattern=NOQUEUE: SYSERR\(sys\): can not chdir\(/var/spool/clientmqueue/\): Permission denied
    
    # these guys are broken, apparently - all MX boxes are not responding
    type=Suppress
    ptype=RegExp
    pattern=timeout writing message to .*\.timesgroup.com.: Broken pipe
    
    # erroneous errors from sendmail
    type=Suppress
    ptype=RegExp
    pattern=collect: I/O error on connection from
    
    # ignore putbody errors
    type=Suppress
    ptype=RegExp
    pattern=putbody
    
    # dserver2 is dying...
    type=Suppress
    ptype=SubStr
    pattern=dserver2 kernel:
    This is a sec.rules file, full of things we want to react too:

    Note: again, all the "patterns" are things that appear in my log files I want to know about.

    Code:
    # This is the rules file for SEC
    # This is used via syslog-ng 
    # Company
    # Author:  Me
    # July 3rd, 2007
    #
    #
    ##########
    # This section was moved to sec.ignore
    ########## End of ignores
    
    # Watch for mail forwarding loops
    type=Single
    ptype=RegExp
    pattern=mail forwarding loop
    desc=$0
    action=pipe 'Mail forwarding loop errors detected $0' /usr/bin/mail -s "Mail Forwarding Loop errors found" "unix-admins@company1.com"
    
    # Watch for sendmail system problems - possible out of memory errors
    type=Single
    ptype=RegExp
    pattern=SYSERR
    desc=$0
    # now add this error to SYSERR in memory, collect them for 30 seconds, then
    # email them all together as 1, instead of many many emails
    action=add SYSERR; set SYSERR 30 (report SYSERR /usr/bin/mail -s "SEC warnings" "unix-admins@company1.com")
    
    # Watch for memory errors
    # then collect ^CPU errors and email unix-admins
    type=Pair
    ptype=RegExp
    pattern=machine check error
    desc=$0
    action=pipe '$0' /usr/bin/mail -s "CPU/Memory errors" "unix-admins@company1.com"
    ptype2=RegExp
    pattern2=^CPU
    desc2=$0
    action2=add CPU; set CPU 30 (report CPU /usr/bin/mail -s "CPU warnings" "mleo@company1.com")
    
    
    # Check for nic duplex errors (usually from boots)
    type=Single
    ptype=RegExp
    pattern=(?i)Half.Duplex 
    desc=$0
    action=pipe '$0' /usr/bin/mail -s "SEC warnings: Duplex issues" "unix-admins@company1.com"

    As you can see, if you can write a RegExp, you can filter for it and react to it.

    Additionally, you can do combinations of things, like, if you see an NFS warning, but then see an NFS OK message within 10 seconds, simply ignore it and chalk it up to network issues.

    Or, if you see kernel: errors, collect them all together for 30 seconds, and send 1 email, rather than flooding unix-admins with important, but very redundant spam.

    You can even call extrernal scripts. For instance, if you see ftp login failures, run a script to restart ftpd or similar.

    Again, check out the official docs for specifics on how to get that granular, and that robust.



    If you are a system admin and responsible for any hosts or hardware, you'd be remiss if you didn't take an hour or two to setup this simple configuration.

    A cheap server with free software that can make your life so much easier is within any IT budget.
    Last edited by happybunny; 07-07-2007 at 09:33 PM.
    m1ke_l
    Lenovo x120e (gave my wife the Asus 1015N)http://justlinux.com/forum/showthrea...hreadid=153955
    Fedora 16 (but I haven't settled yet)
    8gigs of RAM (in a NETBOOK!!)
    Boston, MA USA/Wondering

    My dad's website (he'll love the traffic) http://www.cafephotos.net/

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