Прочитал в man smb.conf, что samba4 научилась сама создавать домашние каталоги:
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SPECIAL SECTIONSДействительно может. Но только при соблюдении следующих условий:
The [global] section
Parameters in this section apply to the server as a whole, or are defaults for sections that do not specifically define certain items. See the notes under PARAMETERS for more information.
The [homes] section
If a section called [homes] is included in the configuration file, services connecting clients to their home directories can be created on the fly by the server.
When the connection request is made, the existing sections are scanned. If a match is found, it is used. If no match is found, the requested section
name is treated as a username and looked up in the local password file. If the name exists and the correct password has been given, a share is
created by cloning the [homes] section.

