I have been having trouble for weeks with very slow boot up times. Last evening, I reapproached the problem. Systemd-analyze timed a boot up at 83 seconds.
I discovered that, although I had disabled network-manager in systemd, dbus was spending time looking for it. I could not find a "clean" way to prevent this, so I renamed the dbus service files in /user/share/dbus-1/system-services for network-manager and modem-manager. The next bootup was down to 44 seconds.
Then, I found that Avahi-daemon was taking a long time to start, so I disabled it in systemd. Now, my bootup is down to 23 sec. Much, much better.
Does anyone know the proper way to disable the dbus system services? I'm sure that renaming their service files is not the correct way.
Tim