15. Journald

15.1. What is “journald”?

Journald is a system for collecting logs and data from devices running “systemd”. Many distributions have moved away standard syslog services in favor of “journald”. The concept is to replace standard “text” base logging for a more “database” binary logging approach.

While this method has advantages, there are several limitations. Software like “Sagan” doesn’t natively read “journald” files. Journald also lacks the ability to send logs to a remote host. Journald relies on services like syslog-ng and rsyslog to send logs to a remote host. While there are some methods to send logs to a remote host via Journald, most are not mature and more of a “proof of concept” than a solution. This makes using a service like syslog-ng or rsyslog the best method to send logs generated by Journald.

15.2. Analyzing journald logs locally

Using the “Journald” command journalctl, it is possible to create a JSON stream representing Journald data. Using Sagan built in JSON processing, it is possible to analyze this data. As Journald writes log data, the journalctl converts it to JSON and sends it to stdout. This can be redirected to a named pipe (FIFO). For example, journalctl -f -o json > /var/sagan/fifo/journald.fifo will direct log data to a named pipe which Sagan can read. Within the Sagan configuration file, you would want to set the following options:

input-type: json                       # pipe or json
json-map: "$RULE_PATH/json-input.map"  # mapping file if input-type: json
json-software: journald                # by "software" type.

15.3. Analyzing journald logs remotely

In situations where syslog-ng or rsyslog is not an option, you can using journalctl to send logs to a remote host in raw JSON. For example, journalctl -f -o json | nc 1514. This would using netcat to send logs to on port 1514. Your receiver would need to be configuration to accepts incoming connection and date in a __raw__ format (non-syslog). Sagan could then be used on the receiving side to analyze data from various devices. You would likely want to wrap the “journalctl” in a script and infinite loop so journalctl will automatically restart if the TCP log connection is broken.