`systemd-analyze` - analyse system boot performance and unit files

systemd-analyze [time|blame|critical-chain|verify|security|calendar|unit-paths] [ARG]

Options you will use

time: How long the boot took, split kernel / userspace.
blame: Units ordered by how long they took to start. Slow != blocking.
critical-chain [UNIT]: The chain that actually delayed the boot, with @start and +duration.
verify FILE: Parse a unit file and report problems without loading it.
security [UNIT]: Score a service's exposure, 0 (locked down) to 10 (wide open).
calendar SPEC: Explain an OnCalendar= expression and show the next elapse.
unit-paths: The unit search path, in precedence order.

$ systemd-analyze verify /etc/systemd/system/demo.service

catches the [Service]/[Unit] mix-ups before you reload

$ systemd-analyze calendar "Mon *-*-* 09:00:00"

next Monday 09:00

Try systemd-analyze in a real terminal Free, in your browser - a real Ubuntu terminal to try it in, with missions that check your work.