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How to determine which daemons are active at Ubuntu boot time before the systemd-logind.service daemon is executed and does not depend on the systemd-logind.service daemon?

I don't get an answer from strace and journalctl software. I want to find the Dependencies of daemons with systemd-logind.service.

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I have been following these instructions for some time, but it is not really clear (it answer is complicated).

I can't clearly get the dependencies of service or daemon For example: systemctl list-dependencies systemd-logind.service --before systemctl list-dependencies systemd-logind.service --after

With these methods, it is not possible to find only the dependencies of a service, because the execution of services at the same time in parallel does through (systemd is a system and service manager ).

It is not at all possible to clearly follow and understand the dependencies of a service. it is hard.

Even, for example, we want to see what steps and calls the executed or called service has with commands: (strace -e trace=signal ping 8.8.8.8 -c 4). Again, there is no indication of services and daemons that issue functionality.

This website gives some pointers. https://insujang.github.io/2018-11-22/systemd-boot-process/

But if we try to narrow it down, it gets more confusing.

hami zahedi
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  • You should be able to deduce this by examining the output of systemd-analyze plot > boot_analysis.svg. That will create a graphical picture of the boot process – PonJar Jul 10 '22 at 09:57
  • Look at this part(open systemd-logind.servcie file) ( [Unit] Documentation=man:systemd-logind.service(8) Wants=user.slice modprobe@drm.service After=nss-user-lookup.target user.slice modprobe@drm.service ConditionPathExists=/lib/systemd/system/dbus.service) .......... Many services are called in the first steps of the boot. It does not correctly show what other services it depends on. The graph does not show dependencies correctly.! ........

    My goal is to specify and clearly understand if the systemd-logind.service covers what chain of communication between services?

     – hami zahedi Jul 10 '22 at 11:15
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    Does this answer your question? Command to list systemd services that run on startup in the order in which they run? – Raffa Jul 22 '22 at 06:40
  • It would be easier to get help if you ask about the actual problem you want to solve and include examples of your attempted solution ... i.e. talk about what exactly you want to achieve at the end and not about the solution you are trying to implement right now. – Raffa Jul 22 '22 at 06:46

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Having done a little research it appears there is a command for this.

systemctl list-dependencies systemd-logind.service
PonJar
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