[Samba] smb.conf different between first DC and replica DC

[Brian Candler]

Under ubuntu 16.04, compiling samba 4.5.1 from source, I've created an 
initial DC and a replica DC by following:

https://wiki.samba.org/index.php/Setting_up_Samba_as_an_Active_Directory_Domain_Controller
https://wiki.samba.org/index.php/Joining_a_Samba_DC_to_an_Existing_Active_Directory

For the second one I had to add the extra DNS records as per:
https://wiki.samba.org/index.php/Verifying_and_Creating_a_DC_DNS_Record

Now, I think it's worked OK. However I see there are two lines in 
smb.conf on the first server which aren't in the second server:

     idmap_ldb:use rfc2307 = yes
     xattr_tdb:file = /usr/local/samba/var/locks/xattr.tdb

Should I add these to the second machine? As I understand it, DCs should 
be identical peers (except for the FSMO roles), which is why I'm 
suspicious of the differences, or if it means I've made a mistake 
configuring the replica.

FYI, the commands I used were:

(1) samba-tool domain provision --server-role=dc --use-rfc2307 
--dns-backend=SAMBA_INTERNAL --realm=AD.EXAMPLE.NET --domain=AD

(2) samba-tool domain join ad.example.net DC -U'AD\administrator'

Thanks,

Brian.