[Samba] Packages necessary to set up a Samba AD controller on Ubuntu?

[Patrick Goetz]

Hi -

I'm setting up a Samba AD controller for the first time, and have been 
looking over available documentation and Internet HOWTOs. I'm a bit 
confused about what packages need to be installed for Ubuntu 20.04.

According to the Samba Wiki, I need:

  acl attr samba samba-dsdb-modules samba-vfs-modules winbind 
libpam-winbind libnss-winbind  libpam-krb5 krb5-config krb5-user

with the cryptic note:
Note: For a DC you do not need libpam-winbind libnss-winbind 
libpam-krb5, unless you require AD users  to login

I think this means I only need these packages if I plan to have AD users 
log in directly to the AD server? I don't, why would anyone want this? 
This leaves:

   acl attr samba samba-dsdb-modules samba-vfs-modules winbind 
krb5-config krb5-user

I'm pretty sure acl and attr are installed by default on Ubuntu 20.04 
server.

However, my question has to do with samba-dsdb-modules and 
samba-vfs-modules packages.

None of the online howto's I've looked at install these packages. For 
example, this seems to be the typical minimal package list:

   samba krb5-user krb5-config winbind smbclient

(krb5-config is a dependency of krb5-user and could be omitted)

What exactly are they needed for?  The Ubuntu package descriptions are 
sufficiently vague that it's not clear.

Thanks;