Samba AD schema extensions
Schema extension in Samba 4
Samba 4 supports same kind of schema extensions as Microsoft Active Directory. Generally speaking schema update in AD is a sensitive action and you must be prepared to restore the DC holding the role of schema master if something goes wrong.
This is even more true in Samba 4 not always generate some critical attributes, that are generated on Microsoft AD, this lack of attribute could lead to a unstartable samba provision. That's why currently schema updates in Samba 4 are disabled by default.
In order to allow them, the option dsdb:schema update allowed has to be set to true in the smb.conf or passed on the command line.
Tested Schema extension
As getting an LDIF that won't ruined the provision can be hard the following of this page will list LDIFs that are known not to break the database.
cat automount_template.ldif | sed 's/DOMAIN_TOP_DN/DC=s4,DC=samba,DC=home,DC=matws,DC=net/'