Journal

The journal is the logging facility provided by the systemd suite, managed by the systemd-journald service. Unlike text-file logging (for example /var/log/syslog or /var/log/messages), the journal captures system and service messages in a binary format, which supports indexed queries and integrity checks.

Journal data is stored in journal files. By default these live at:

• /run/log/journal/ for volatile logs, which are held in memory and lost on reboot.
• /var/log/journal/ for persistent logs, which are written to disk and survive reboots.

If /var/log/journal/ exists, logs are persistent; otherwise they remain volatile. The binary format means the content cannot be read with tools such as cat or less; the journalctl command is used to query and display entries.

Journal output is represented by the Journal variant of the Tracer object (found in the WebUI under Settings › Telemetry › Tracers). The variant carries no variant-specific fields; only the common tracer fields apply (enable, level, lossy, events, eventsPolicy).

For example:

{
  "@type": "Journal",
  "enable": true,
  "level": "info"
}

The Journal variant is only available on Linux systems running systemd.