Just to let you know that I have made considerable progress with the Centos7-armv7 based server on a cubietruck.
There is a LOT of services that are needed for a Samba AD:
Time keeping - I am using Chrony DNS - Bind DHCP - dhcpd Samba/ldap/kerberos - sernet
cups is installed, but I am going to remove it from the AD.
Lots of steps to get all this working. One of the regulars on the Samba list gave me a script to handle the dyndns via dhcp. He had to change what he had to work with Centos.
The point here is I am exercising more than just the Sernet code that Nicolas so kindly built for me.
I also have cups installed, but I am going to change my smb.conf to remove printing support on the AD; the file server should do that, so that is one less service needed. Right now with it I am seeing:
# free total used free shared buff/cache available Mem: 2062396 174948 1647400 24824 240048 1832628 Swap: 999420 0 999420
So it should run on a Cubieboard2 with only 1Gb memory.