Domain Controller

A domain controller in Windows NT is functionally similar to a Network Information Service (NIS) server in a Linux environment. Domain controllers and NIS servers both host user/group information databases as well as related services. Domain controllers are mainly used for security, including the authentication of users accessing domain resources. The service that maintains the user/group database integrity is called the Security Account Manager (SAM). The SAM database is stored differently between Windows and Linux Samba-based systems, therefore SAM replication cannot be achieved and platforms cannot be mixed in a PDC/BDC environment.

In a Samba environment, there can be only one PDC and zero or more BDCs.

Samba cannot exist in a mixed Samba/Windows domain controller environment (Samba cannot be a BDC of a Windows PDC or vice versa). Alternatively, Samba PDCs and BDCs can coexist.

Primary Domain Controller (PDC) using `tdbsam`

The simplest and most common implementation of a Samba PDC uses the tdbsam password database backend. Planned to replace the aging smbpasswd backend, tdbsam has numerous improvements that are explained in more detail in "Samba Account Information Databases". The passdb backend directive controls which backend is to be used for the PDC.

[global]
workgroup = DOCS
netbios name = DOCS_SRV
passdb backend = tdbsam
security = user
add user script = /usr/sbin/useradd -m "%u"
delete user script = /usr/sbin/userdel -r "%u"
add group script = /usr/sbin/groupadd "%g"
delete group script = /usr/sbin/groupdel "%g"
add user to group script = /usr/sbin/usermod -G "%g" "%u"
add machine script = /usr/sbin/useradd -s /bin/false -d /dev/null  -g machines "%u"
# The following specifies the default logon script
# Per user logon scripts can be specified in the user
# account using pdbedit logon script = logon.bat
# This sets the default profile path.
# Set per user paths with pdbedit
logon drive = H:
domain logons = Yes
os level = 35
preferred master = Yes
domain master = Yes
[homes]
 comment = Home Directories
 valid users = %S
 read only = No
[netlogon]
 comment = Network Logon Service
 path = /var/lib/samba/netlogon/scripts
 browseable = No
 read only = No
# For profiles to work, create a user directory under the
# path shown.
mkdir -p /var/lib/samba/profiles/john
[Profiles]
 comment = Roaming Profile Share
 path = /var/lib/samba/profiles
 read only = No
 browseable = No
 guest ok = Yes
 profile acls = Yes
# Other resource shares ... ...

To provide a functional PDC system which uses the tdbsam follow these steps:

Use a configuration of the smb.conf file as shown in the example above.

Add the root user to the Samba password database.
```
smbpasswd -a root
Provide the password here.
```
Start the smb service.
Make sure all profile, user, and netlogon directories are created.

Add groups that users can be members of.

groupadd -f users
groupadd -f nobody
groupadd -f ntadmins

Associate the UNIX groups with their respective Windows groups.

net groupmap add ntgroup="Domain Users" unixgroup=users
net groupmap add ntgroup="Domain Guests" unixgroup=nobody
net groupmap add ntgroup="Domain Admins" unixgroup=ntadmins

Grant access rights to a user or a group. For example, to grant the right to add client machines to the domain on a Samba domain controller, to the members to the Domain Admins group, execute the following command:
```
net rpc rights grant 'DOCS\Domain Admins' SetMachineAccountPrivilege -S PDC -U root
```
Keep in mind that Windows systems prefer to have a primary group which is mapped to a domain group such as Domain Users.
Windows groups and users use the same namespace thus not allowing the existence of a group and a user with the same name like in UNIX.
If you need more than one domain controller or have more than 250 users, do not use a tdbsam authentication backend. LDAP is recommended in these cases.

Primary Domain Controller (PDC) with Active Directory

Although it is possible for Samba to be a member of an Active Directory, it is not possible for Samba to operate as an Active Directory domain controller.

Primary Domain Controller (PDC) using tdbsam

Primary Domain Controller (PDC) with Active Directory

Primary Domain Controller (PDC) using `tdbsam`