[Samba] Making a Samba DC under a different domain

[Brian Candler]

I am trying to determine if it is mandatory for the domain controllers's 
host FQDN to be within the same DNS domain as the realm's DNS domain.

For example: let's say I want the DC to be called smb1.int.example.net 
but I want the realm to be AD.EXAMPLE.NET.

I set "smb1" in /etc/hostname and mapping to the FQDN in /etc/hosts, so 
that "hostname -f" shows the desired FQDN "smb1.int.example.net".

Then I run samba-tool domain provision --interactive, and change the 
offered realm from INT.EXAMPLE.NET to AD.EXAMPLE.NET. I then end up with:

Server Role:           active directory domain controller
Hostname:              smb1
NetBIOS Domain:        AD
DNS Domain:            ad.example.net
DOMAIN SID: S-1-5-21-895328253-630460385-2547770178

And LDAP contains:

# SMB1, Domain Controllers, ad.example.net
dn: CN=SMB1,OU=Domain Controllers,DC=ad,DC=example,DC=net
objectClass: top
objectClass: person
objectClass: organizationalPerson
objectClass: user
objectClass: computer
cn: SMB1
...
name: SMB1
...
dNSHostName: smb1.ad.example.net
...
servicePrincipalName: HOST/smb1.ad.example.net
servicePrincipalName: HOST/smb1.ad.example.net/AD
servicePrincipalName: ldap/smb1.ad.example.net/AD
...

So it seems to have chosen smb1.ad.example.net (instead of 
smb1.int.example.net) for its hostname. Is that a hard-and-fast rule or 
can it be bypassed, and if so how?

Thanks,

Brian.