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SC4S Logging and Troubleshooting Resources

Helpful Linux and Container Commands

Linux service (systemd) commands

  • Check service status systemctl status sc4s
  • Start service systemctl start service
  • Stop service systemctl stop service
  • Restart service systemctl restart service
  • Enabling service at boot systemctl enable sc4s
  • Query the system journal journalctl -b -u sc4s

Container Commands

  • NOTE: All container commands below can be run with either runtime (podman or docker).

  • Container logs sudo podman> logs SC4S

  • Exec into SC4S container podman exec -it SC4S bash
  • Rebuilding SC4S volume
podman volume rm splunk-sc4s-var
podman volume create splunk-sc4s-var
  • Pull an image or a repository from a registry podman pull splunk:scs:latest
  • Remove unused data podman system prune
  • Load an image from a tar archive or STDIN podman load <tar>

Obtaining “On-the-wire” Raw Events

In almost all cases during development or troubleshooting, you will need to obtain samples of the messages exactly as they are received by SC4S. These “raw” events contain the full syslog message (including the <PRI> preamble) and differs from those that appear in Splunk after processing by sc4s and/or Splunk. This is the only way to determine if SC4S parsers and filters are operating correctly, as raw messages are needed for “playback” when testing. In addition, the community supporting SC4S will always first ask for raw samples (kind of like the way Splunk support always asks for “diags”) before any development or troubleshooting exercise.

Here are some options for obtaining raw logs for one or more sourcetypes:

  • Run tcpdump on the collection interface and display the results in ASCII. You will see events of the form
<165>1 2007-02-15T09:17:15.719Z router1 mgd 3046 UI_DBASE_LOGOUT_EVENT [junos@2636. username="user"] User 'user' exiting configuration mode

buried in the packet contents.

  • Set the variable SC4S_SOURCE_STORE_RAWMSG=yes in env_file and restart sc4s. This will store the raw message in a syslog-ng macro called RAWMSG and will be displayed in Splunk for all fallback messages. For most other sourcetypes, the RAWMSG is not displayed, but can be surfaced by changing the output template to one of the JSON variants (t_JSON_3164 or t_JSON_5424 depending on RFC message type). See SC4S metadata configuration for more details.

** IMPORTANT! Be sure to turn off the RAWMSG variable when you are finished, as it doubles the memory and disk requirements of sc4s. Do not use RAWMSG in production!

  • Lastly, you can enable the alternate destination d_rawmsg for one or more sourcetypes. This destination will write the raw messages to the container directory /var/syslog-ng/archive/rawmsg/<sourcetype> (which is typically mapped locally to /opt/sc4s/archive). Within this directory, the logs are organized by host and time. This method can be useful when raw samples are needed for events that partially parse (or parse into the wrong sourcetype) and the output template is not JSON (see above).

“exec” into the container (advanced)

You can confirm how the templating process created the actual syslog-ng config files that are in use by “exec’ing in” to the container and navigating the syslog-ng config filesystem directly. To do this, run

/usr/bin/podman exec -it SC4S /bin/bash

and navigate to /opt/syslog-ng/etc/ to see the actual config files in use. If you are adept with container operations and syslog-ng itself, you can modify files directly and reload syslog-ng with the command kill -1 1 in the container. You can also run the / script by hand (or a subset of it, such as everything but syslog-ng) and have complete control over the templating and underlying syslog-ng process. This is an advanced topic and futher help can be obtained via the github issue tracker and Slack channels.

Keeping a failed container running (even more advanced)

When debugging a configuration syntax issue at startup, it is often helpful to keep the container running after a syslog-ng startup failure. In order to facilitate troubleshooting and make “on the fly” syslog-ng configuration changes from within a running container, the container can be forced to remain running when syslog-ng fails to start (which normally terminates the container). This can be enabled by adding SC4S_DEBUG_CONTAINER=yes to the env_file. Use this capability in conjunction with “exec-ing” into the container described above.

  • NOTE: Do not attempt to enable the debug container mode while running out of systemd. Run the container manually from the CLI, as podman or docker commands will be required to start, stop, and optionally clean up cruft left behind by the debug process. Only when SC4S_DEBUG_CONTAINER is set to “no” (or completely unset) should systemd startup processing resume.