Upgrade from S3 to a Samba4 DC [with LDAPSAM]

[Adam Tauno Williams]

Quoting tataia <iongigixx at gmail.com>:
> Yes. It is possible. But you must have on s4  smb.conf and tdb's  from s3

[root at localhost samba-master]# pwd
/root/samba-master

S4 is compiled and installed; no issues.

1, I copied the production S3 domains /etc/samba/smb.conf to the local  
S4 test server as smb.conf in the current directory.
2. I copied the contents of the production S3 DC's /var/lib/samba/ to  
the local directory /root/s3
3. I copied the file /etc/samba/secrets.tdb from the production S3 box  
into the local directory /root/s3
4. I edited the smb.conf file adding:

private dir = /root/s3
realm = EXAMPLE.COM

5. I change the ldapsam reference in smb.conf from an ldapi://.... url  
to point to a ldap://{ip}

6. I run the upgrade script

[root at localhost samba-master]# ./source4/setup/upgrade_from_s3  
smb.conf /tmp/x --libdir=/root/s3
You are not root or your system do not support xattr, using tdb  
backend for attributes. If you intend to use this provision in  
production, rerun the script as root on a system supporting xattrs.
Reading smb.conf
Provisioning
/root/s3/secrets.tdb
No builtin nor plugin backend for ldapsam found
Traceback (most recent call last):
   File "./source4/setup/upgrade_from_s3", line 129, in <module>
     upgrade_from_samba3(samba3, logger, targetdir,  
session_info=system_session(), useeadb=eadb)
   File "bin/python/samba/upgrade.py", line 492, in upgrade_from_samba3
     s3db = samba3.get_sam_db()
   File "bin/python/samba/samba3/__init__.py", line 387, in get_sam_db
     return passdb.PDB(self.lp.get('passdb backend'))
passdb.error: Cannot load backend methods for  
'ldapsam:ldap://192.168.1.9/' backend (-1073741811,Unexpected  
information received)