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Asked: 2024-12-31T11:59:38+05:30

How can I configure syslog-ng to manage specific inclusions and exclusions for log sources effectively? I’m looking for guidance on filtering certain log messages while allowing others to pass through in my syslog-ng setup.

anonymous user

I’ve been diving into configuring syslog-ng for my logging infrastructure, and I’m running into a bit of a challenge that I hope someone here can help me with. So, I need to set up syslog-ng to manage specific inclusions and exclusions for my log sources, but it’s turning out to be more complicated than I initially thought.

Here’s the situation: I’ve got a bunch of different servers and devices sending logs that I want to centralize. However, not all log messages are created equal. For example, on some of my application servers, I want to capture everything related to authentication failures since that’s critical, but I want to filter out verbose debug messages that just clutter everything up. On the other hand, I have some infrastructure components, like firewalls, where I want to log everything because you never know if something might happen.

I’ve read the syslog-ng documentation and some blogs, but the filtering and managing messages based on priorities and content can get tricky. How can I effectively set up my syslog-ng to only allow desired log messages while excluding the ones that are just noise?

Also, it would be super helpful to know if there are particular patterns or syntax I should be aware of when writing these filters. I’ve seen some examples online, but they seem very generic, and I’m concerned about how to adapt them to my specific needs.

If anyone has experience with this or could share a simplified example of the configuration, it would be amazing! I’d love to see how you handle your inclusions and exclusions, especially in terms of maintaining a balance between getting critical logs and avoiding log bloat. Thanks for any tips or insights you can share—I really want to get this right and make my logging much more effective.

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    2 Answers

    1. anonymous user

      Configuring syslog-ng for Inclusions and Exclusions

      So, it sounds like you’re on the right track, but those filters can be a bit tricky to figure out at first. Here’s a simple approach you can take to tackle your requirements.

      Basic Configuration

      You’ll want to define different sources for your logs and then set up some filters based on your needs.

              
            # Define a source for your application servers
            source s_app_servers {
                tcp(ip("0.0.0.0") port(514));
            };
            
            # Define a source for your infrastructure components
            source s_infrastructure {
                udp(ip("0.0.0.0") port(514));
            };

            # Filter for critical authentication failure logs
            filter f_auth_failures {
                facility(auth) and level(err);
            };

            # Filter to exclude debug messages from application servers
            filter f_exclude_debug {
                facility(local5) and level(debug);
            };

            # Log configuration for application servers
            log {
                source(s_app_servers);
                filter(f_auth_failures);
                destination(d_auth_logs);
            };

            # Log configuration for infrastructure logs
            log {
                source(s_infrastructure);
                destination(d_all_logs);
            };

      Key Points

      • Sources: Define where your logs come from, like TCP or UDP.
      • Filters: Use facility and level to include or exclude logs. Adjust based on what you want to capture.
      • Destinations: Make sure you’re sending your filtered logs to the right place.

      Patterns and Syntax

      Keep these patterns in mind:

      • facility: This tells syslog-ng the source of your logs. Use it carefully to capture specific applications.
      • level: Helps define the severity of the messages you want to include/exclude, like info, warning, error, etc.
      • You can combine filters with and or or depending on what you need.

      Feel free to tweak the configuration as per your setup. Once you’ve added these configurations, restart syslog-ng to see how well it filters the logs based on your requirements!

      Good luck, and don’t hesitate to ask if you get stuck on something specific!

    2. anonymous user

      To effectively set up syslog-ng for your logging infrastructure, you can use filters to include or exclude specific log messages based on their content and severity. In your case, you’ll want to create conditions that capture critical authentication failures while discarding verbose debug messages. For instance, you can utilize the filter directive in your configuration file. A sample configuration might look like this:

      filter f_auth_fail {
    facility(auth) and level(err);
};

filter f_debug_exclude {
    facility(auth) and level(debug);
};

destination d_auth_logs {
    file("/var/log/auth_failures.log");
};

destination d_all_logs {
    file("/var/log/all_syslogs.log");
};

log {
    source(s_src);
    filter(f_auth_fail);
    destination(d_auth_logs);
};

log {
    source(s_src);
    filter(f_debug_exclude);
    destination(d_all_logs);
};

      This example includes authentication failures in a separate log file and ensures that debug messages are not included in your primary log streams. Adjusting the filter definitions allows you to control what gets logged. Additionally, for your firewalls, you might want to use a broader filter such as filter f_firewall { level(info); }; to capture all messages without exclusions. Be sure to test your configuration in a staging environment to refine your filters based on actual log patterns you encounter. Documentation includes many built-in macros and syntax examples which can also be tailored to your specific use cases, helping to maintain a balance between critical logs and avoiding unnecessary log bloat.