Plain text backends are nothing more than the /etc/passwd type backends. With a plain text backend, all usernames and passwords are sent unencrypted between the client and the Samba server. This method is very unsecure and is not recommended for use by any means. It is possible that different Windows clients connecting to the Samba server with plain text passwords cannot support such an authentication method.

A popular backend used in previous Samba packages, the smbpasswd backend utilizes a plain ASCII text layout that includes the MS Windows LanMan and NT account, and encrypted password information. The smbpasswd backend lacks the storage of the Windows NT/2000/2003 SAM extended controls. The smbpasswd backend is not recommended because it does not scale well or hold any Windows information, such as RIDs for NT-based groups. The tdbsam backend solves these issues for use in a smaller database (250 users), but is still not an enterprise-class solution.

The ldapsam_compat backend allows continued OpenLDAP support for use with upgraded versions of Samba. This option normally used when migrating to Samba 3.0.

The tdbsam backend provides an ideal database backend for local servers, servers that do not need built-in database replication, and servers that do not require the scalability or complexity of LDAP. The tdbsam backend includes all of the smbpasswd database information as well as the previously-excluded SAM information. The inclusion of the extended SAM data allows Samba to implement the same account and system access controls as seen with Windows NT/2000/2003-based systems.

The tdbsam backend is recommended for 250 users at most. Larger organizations should require Active Directory or LDAP integration due to scalability and possible network infrastructure concerns.

The ldapsam backend provides an optimal distributed account installation method for Samba. LDAP is optimal because of its ability to replicate its database to any number of servers using the OpenLDAP slurpd daemon. LDAP databases are light-weight and scalable, and as such are preferred by large enterprises.

If you are upgrading from a previous version of Samba to 3.0, note that the /usr/share/doc/samba-<version>/LDAP/samba.schema has changed. This file contains the attribute syntax definitions and objectclass definitions that the ldapsam backend will need in order to function properly.

As such, if you are using the ldapsam backend for your Samba server, you will need to configure slapd to include this schema file. Refer to Section 24.5, “The /etc/openldap/schema/ Directory” for directions on how to do this.

The mysqlsam backend uses a MySQL-based database backend. This is useful for sites that already implement MySQL. At present, mysqlsam is now packed in a module separate from Samba, and as such is not officially supported by Samba.