[Samba] authentication issues

[peter lawrie]

Hopefully this is a simple problem for a guru to solve.

I  have been installing Centos / Samba servers for my clients since 2004.
However, in almost every instance, the linux machine has been the only
server on site. To begin with I set up the server as a domain server but as
most of my customers have less than a dozen PCs on a single site, the
domain seemed to be an overkill so I now tend to use the server as a member
of a workgroup, and purely as a fileserver.

I installed a centos 5 server for a customer in 2012. As centos 5 support
has ended, I recently persuaded that customer that it was time to update
their server.
I set up a new Dell T130 server with centos 7 and the latest downloaded
samba.
This was initially done offsite using my own windows 10 pro PC as a client,
I added all the users and passwords before taking the server to site.
All PCs on site were running win10 pro, version 1709, and previously had
been connected to the centos 5 server, with the lanman parameters on the
PCs modified to suit.

When I connected the centos 7 server, I noted that PCs logged on as any of
the users had access to the two shares I had defined but not to their
personal home directories.
Once I had completed restoring the data from backup disks, (only to the
shares) for a reason I still do not understand I lost connection to the
shares as well.
I rebuilt smb.conf several times without success, but  when I added " ntlm
auth = yes " it  worked again and I could access the home directories as
well. I think I may have downgraded the authentication, but the customer is
happy.

Can anyone explain what the issue may have been, the effect of my fix and
whether I should go back and 'improve' the setup?
Peter Lawrie