Is there any way to list systemd services in linux "in-the-order-of" they were loaded?

Question

I am trying to understand the dependencies between different systemd services in my new project. We are using yocto build system and systemd/system services.

If I perform,

systemctl -l

It will list all the services in alphabetic order. But I am specifically looking for any commands/scripts that can be used for listing systemd services "in-the-order-of" they were loaded.

Please help.

Autism

Try systemctl list-dependencies. I think this is what you are looking for. – Ypsilanti

systemctl list-dependencies will not account for more subtle service startup order, the correct answer is given by shibley (systemd-analyze plot) – Smutch

Answer 1

Unfortunately, due to the parallel nature of the boot up process and the potentially complex dependency relationships among services, the service start up order isn't very deterministic. However, systemd-analyze, if present on your system, can graphically plot the start up order of services:

systemd-analyze plot > startup_order.svg

It can also be used to graphically plot service dependencies:

systemd-analyze dot | dot -Tsvg > systemd.svg

Electronarcosis

Cool stuff! Congrats for the post – Nidify

On dependency plot --order --require might be useful: selects which dependencies are shown in the dependency graph. – Riel

Answer 2

@shibley's tip with systemd-analyze is Great. Adding other helpful systemd-analyze commands here as I can't comment yet ...

1. Finding which service have the biggest impact on the boot time:

   systemd-analyze blame
   

2. Print a tree in the terminal of the service dependencies with timing impact

   systemd-analyze critical-chain
   

Methacrylate