毎度のように調べているので。楽にコピペできるように自分用メモ。
# Switch to root user
sudo su -
# Show user-data file
cat /var/lib/cloud/instance/user-data.txt
# Show cloud-init log
cat /var/log/cloud-init-output.log
# Show service file
systemctl cat my-awesome.service
# Show service status
systemctl status my-awesome.service
# Show the last 50 lines of the journal for the service (current boot)
journalctl -u my-awesome.service -b -n 50
# Show the first 50 lines of the journal for the service (current boot)
journalctl -u my-awesome.service -b --reverse | tail -n 50
# Follow service log in real-time
journalctl -u my-awesome.service -f