Query the systemd journal

  • Show all messages from this [b]oot: journalctl -b

  • Show all messages from last [b]oot: journalctl -b -1

  • Show all messages with priority level 3 (errors) from this [b]oot: journalctl -b –priority=3

  • [f]ollow new messages (like tail -f for traditional syslog): journalctl -f

  • Show all messages by a specific [u]nit: 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

Log files 

/var/log/
startx > $HOME/startx.log 2>&1
$ startx &> ~/.Xoutput