Starting with network Security and Hardening Guide

It started with a minor problem with an NFS share with a NAS which grew arms and legs.

Having read some of the excellent Leap 15.3 guides on NFS and system security I have found that there are many overlapping or complementary services and tools.

This is not a surprise to me as a Linux user, but I am now lost: DNS, PAM, NIS, Yast, LDAP, Kerberos, Active Directory etc. Where to start so that I can proceed one step at a time and keep everything running as I do so.

Any suggested up-to-date reading for soho user with mixed Linux & M$ machines which have to work together but are on different subnets. It would be much appreciated.