journalctl

Query the systemd journal.

• Show all messages from this boot:

journalctl -b

• Show all messages from last boot:

journalctl -b -1

• Show all messages with priority level 3 (errors) from this boot:

journalctl -b --priority={{3}}

• Follow new messages (like tail -f for traditional syslog):

journalctl -f

• Show all messages by a specific unit:

journalctl -u {{unit}}

• Filter messages within a time range (either timestamp or placeholders like "yesterday"):

journalctl --since {{now|today|yesterday|tomorrow}} --until {{YYYY-MM-DD HH:MM:SS}}

• Show all messages by a specific process:

journalctl _PID={{pid}}

• Show all messages by a specific executable:

journalctl {{path/to/executable}}