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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.

user3128488
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  • Try `systemctl list-dependencies`. I think this is what you are looking for. – alvits Mar 28 '15 at 00:30
  • `systemctl list-dependencies` will not account for more subtle service startup order, the correct answer is given by shibley (`systemd-analyze plot`) – Edward Aug 28 '19 at 08:17

2 Answers2

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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
shibley
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  • Cool stuff! Congrats for the post – imjoseangel Nov 22 '20 at 17:36
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    On dependency plot `--order --require` [might be useful](https://www.freedesktop.org/software/systemd/man/systemd-analyze.html#Options): selects which dependencies are shown in the dependency graph. – Pablo Bianchi Jul 30 '22 at 05:34
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@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
Alex Waygood
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kral2
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