Operation Manual

8.2.3.3 Review the Complete Start-Up Process
Above mentioned commands let you review the services that started and the time it
took to start them. If you need to know more details, you can tell systemd to verbosely
log the complete start-up procedure by entering the following parameters at the boot
prompt:
systemd.log_level=debug systemd.log_target=kmsg
Now systemd writes its log messages into the kernel ring buffer. View that buffer
with dmesg:
dmesg | less
The systemd daemon 149