[Samba] What is wrong in my Samba setup?

[Jason Long]

Hello,
I use Fedora Server and installed the last version of Samba from the source code on it. My "/etc/hosts" file contents is:

# cat /etc/hosts 
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.56.7 mydc.mydomain.z mydc

And my host name is "mydc":

# hostname
mydc

I used below command to configure Samba as a DC:

# samba-tool domain provision --use-rfc2307 --interactive --option="interfaces=lo enp0s17" --option="bind interfaces only=yes"

And the output is:
https://paste.ubuntu.com/p/8bd7Q42wNH/

The contents of the "/etc/krb5.conf" file is:

[libdefaults]
    default_realm = MYDOMAIN.Z
    dns_lookup_realm = false
    dns_lookup_kdc = true


[realms]
MYDOMAIN.Z = {
    default_domain = mydomain.z
}


[domain_realm]
    mydc = MYDOMAIN.Z


The Samba service is running without any error.

I have some questions:

1- What is realm?

2- When I want to verifying DNS, I got below error:

# host -t SRV _ldap._tcp.mydomain.mydomain.z.
Host _ldap._tcp.mydomain.mydomain.z. not found: 3(NXDOMAIN)

# host -t SRV _kerberos._tcp.mydomain.mydomain.z.
Host _kerberos._tcp.mydomain.mydomain.z. not found: 3(NXDOMAIN)

# host -t A mydc._tcp.mydomain.mydomain.z.
Host mydc._tcp.mydomain.mydomain.z. not found: 3(NXDOMAIN)


Which part of my configuration is wrong?

Thank you.