The samba-ad-dc service is meant for samba when it is configured as an Active Directory Controller. Since your role is "standalone server", the services you should try to start/stop/restart/etc are called smbd and nmbd, as they were before.
You should check why, if still happening, these are failing: sudo systemctl restart smbd nmbd If they are still failing, please attach their output and the logs from /var/log/samba/log* Also please run the testparm utility to verify your smb.conf for syntax. I can't do it with the file you provided because of the bits you sanitized. ** Changed in: samba (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Server, which is subscribed to samba in Ubuntu. https://bugs.launchpad.net/bugs/1776576 Title: Ubuntu 18.04 uograde: samba fails to run To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/samba/+bug/1776576/+subscriptions -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs