System logs with journald

Systemd uses its own service for system logs called journald. The service collects, processes and stores log data from various sources and makes it available via standardized interfaces. Unlike classic text-based log files, journald uses a structured, binary journal format that enables efficient filter and search operations.

In addition, journald automatically provides each log message with metadata (e.g. process ID, user ID, priority, timestamp), enabling structured queries and correlations.

The tool journald is used to access journalctl and the log data it contains.

The following command can be used to display the log entries for a specific service, in this example for the network service systemd-networkd:

sudo journalctl --no-pager --unit systemd-networkd.service

Without parameters, journalctl displays the entire journal content in chronological order.