Migrating a Samba NT4 Domain to Samba AD (Classic Upgrade)

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This guide is only relevant if you have a Samba NT4-style domain, that you want to upgrade to Samba Active Directory!

Many people find themselves in a situation where they have an existing Samba NT4-style domain, complete with an extensive set of domain users, groups and machines. The domain is functioning rather well, but they find themselves running into more and more dead ends. Things that a NT4-style domain just doesn't support.

Samba provides a way to migrate an existing NT4-style domain to a new Samba Active Directory. The following guide describes the upgrade szenario. It is suitable for upgrading an existing Samba installation, as well as running the migrating on a new server, if you had considered e. g. replacing the hardware at the same time.

About classicupgrade

The classicupgrade is a function built into samba-tool. The intent of this function is to do a full replacement of an existing Samba NT4-style domain. It is possible to do the conversion and the users and machines will simply re-connect to the new Samba AD installation without needing to manually re-join.

Doing a classicupgrade is possible from all passwd backends (smbpasswd, tdbsam and ldapsam).

Important notes before you start

The migration from an NT4-style domain to Active Directory is a one way road! This means that when your clients are contacting the first time your migrated AD Domain Controller, then will never access the NT4-style domain any more - even if you rollback your changes!

It's highly recommended, that before you do the migration, you should test the upgrade process in a network, that is separated from your production! This enables you to avoid unnecessary downtimes through unpredictable problems and it won't have any effects to your existing network.

Server information used in this HowTo

Inside this HowTo, we will be using the following configuration/settings:

AD DC Installation Directory:       /usr/local/samba/
AD DC Hostname:                     DC1
AD DNS Name:                        samdom.example.com
Realm:                              samdom.example.com
NT4 Domain Name:                    samdom
IP Address:               
Databases of the Samba NT4-domain:  /usr/local/samba.PDC/dbdir/
smb.conf of the Samba NT4-domain:   /usr/local/samba.PDC/etc/smb.PDC.conf


Upgrading on a new server

If you had chosen to migrate to Samba Active Directory on a different machine, some further steps of preparation are required.


If the backend of your PDC is ldapsam, you're having the choice:

  • let the LDAP backend stay on it's current host, as it is only required for the classicupgrade. Samba AD is shipped with its own LDAP server and won't use the external LDAP server any more. In that case make sure, that you check/adapt your configuration (ldap.conf, smb.conf) to retrieve the information from your old LDAP backend host.
  • install temporary an openLDAP backend on the new host, import the content of your current installation and after the classicupgrade shut it down. The following is just a basic set of steps, typically required for this procedure. Consult your distributions documentation for specific requirements.
  • LDAP export on the old host:
# slapcat > ldap.backup.ldif
  • Copy the export file to your new server
  • Install openLDAP (incl. headers and libraries) on the new host
  • Stop the LDAP service on the new host
  • Import the ldif
# slapadd -l ldap.backup.ldif
  • Check/adjust permissions on your LDAP database directory (distro specific)
# chown -R ldap:ldap /var/lib/ldap/
  • Copy the slapd.conf from your old LDAP host to the new one
  • Start the LDAP service


You also need to transfer several databases and the smb.conf of your old PDC to the new host, as well. The classicupgrade process section will tell you later about everything needed. You just have to copy the required files to the new server before.

Avoiding common problems

Prevent duplicate SIDs abortions

A common problem are duplicate SIDs in the backend. In a healthy environment an SID is unique. But old Samba versions without sanity checks, wrong manual changes or other things could have lead to duplicate SIDs in your environment. These need to be fixed/removed. Otherwise the classicupgrade is not possible!

See: What are the consequences changing an SID/RID?

To detect duplicate SIDs in an LDAP backend, you can use the following script on your LDAP server:

# A quick and dirty python script that checks for duplicat SID's using slapcat.
import os

data = os.popen("slapcat 2>&1 | grep sambaSID", 'r')
line = []
def anydup(thelist):
        dups = list(set([x for x in thelist if thelist.count(x) > 1]))
        for i in dups:
                print "Duplicate id: ", i

for each_line in data:


To find duplicate SIDs on other passdb backends (smbpasswd, tdbsam), you have to script around the output of the following two commands:

# pdbedit -Lv
# net groupmap list

To change SIDs for for groups, remove the mapping and re-add it. A new SID with the next free RID is created and used.

# net groupmap delete ntgroup="demo group"
Sucessfully removed demo group from the mapping db

# net groupmap add ntgroup="Demo Group" unixgroup="demo group"
No rid or sid specified, choosing a RID
Got RID 1009
Successfully added group Demo Group to the mapping db as a domain group

For user and machine accounts, you have to manually assign a new RID:

# net maxrid
Currently used maximum rid: 3001

# pdbedit -U 3002 -u demo1
User SID:   S-1-5-21-4097619914-84555263-3210783664-3002

Prevent common user/group name abortions

If you are having any usernames, that are the same than a groupname, you have to rename one of them. Otherwise the provisioning will fail („ProvisioningError: Please remove common user/group names before upgrade.“). Also, if you have unique groups that, for whatever historical reason, share the same displayName, they will have to edited so that all the displayNames are different.

slapd.conf sizelimit

Note: The following is only relevant in passdb backend = ldapsam setups:

If you have many objects in your PDC LDAP, you should consider to add

sizelimit {<integer>|unlimited}

to your slapd.conf. This parameter specifies the maximum number of entries returned from a search operation. The default, if not set, is 500. This can cause problems, when having many objects in your LDAP directory and classicupgrade can't retrieve them all!

Active Directory Domain Name

Choose a meaningful and suitable Active Directory domain name / realm. See Domain Name best practice.

Note: Currently Samba does not provide capabilities to change the AD Domain Name afterwards!

Domain Controller name

If you consider to change the Domain Controller name during the migration, simply set/change the netbios name in your old PDC smb.conf file, that classicupgrade will use for doing the migration:

netbios name = DC1

Though it's possible to rename a DC afterwards, it is always additional work and can cause problems (forgotten configuration adaptations, etc.)

Installing Samba


This HowTo is frequently updated to reflect the latest changes. Please see the Samba Release Planning for more specifics.

Different ways to install

You have a few options to install Samba:

  • Install binary distribution packages. Make sure, that you use a recent Samba installation with Active Directory Domain Controller capabilities!

See OS Requirements for dependencies and recommendations.


Take care when running Samba commands, if you also have a previous version of Samba installed. To avoid inadvertently running the wrong version, you should consider putting the /usr/local/samba/bin/ and /usr/local/samba/sbin/ directories in the beginning of your $PATH variable!

You can see what version of Samba, if any, is in your $PATH variable, by running:

# samba --version

The classicupgrade process

Before you start, shutdown your Samba PDC services (smbd, nmbd, winbind), but leave your LDAP server running (if using passwd backend = ldapsam).

Rename your Samba PDC installation directory, or at least the folder containing the databases, to avoid mixing binaries/libraries/databases from the old and new installation:

# mv /usr/local/samba/ /usr/local/samba.PDC/

It will also prevent problems, like they will happen, when your old Samba installation is started automatically at boot time again.

Rename your smb.conf to a name indicating, that it's the one from your old PDC:

# mv /usr/local/samba.PDC/etc/smb.conf /usr/local/samba.PDC/etc/smb.PDC.conf

The classicupdate process uses information from databases of your old PDC installation. That's why it is necessary to have them all in one directory. Copy the following databases from your old PDC installation to a new folder. We'll use /usr/local/samba.PDC/dbdir/ in this guide:

# mkdir /usr/local/samba.PDC/dbdir/
# cp -p /usr/local/samba.PDC/private/secrets.tdb /usr/local/samba.PDC/dbdir/
# cp -p /usr/local/samba.PDC/private/schannel_store.tdb /usr/local/samba.PDC/dbdir/
# cp -p /usr/local/samba.PDC/private/passdb.tdb /usr/local/samba.PDC/dbdir/
# cp -p /usr/local/samba.PDC/var/lock/gencache_notrans.tdb /usr/local/samba.PDC/dbdir/
# cp -p /usr/local/samba.PDC/var/locks/group_mapping.tdb /usr/local/samba.PDC/dbdir/
# cp -p /usr/local/samba.PDC/var/locks/account_policy.tdb /usr/local/samba.PDC/dbdir/

The classicupgrade setup a database based on the Samba NT4-style domain SID. A default directory layout is created including accounts, groups, ACLs, etc. Imports of e. g. user and machine accounts are done.

The classicupgrade step must be run as user root. Otherwise you're getting permission denied errors!

To start the classicupgrade with Internal DNS setup, run:

# samba-tool domain classicupgrade --dbdir=/usr/local/samba.PDC/dbdir/ --use-xattrs=yes --realm=samdom.example.com --dns-backend=SAMBA_INTERNAL /usr/local/samba.PDC/etc/smb.PDC.conf

To start the classicupgrade with BIND_DLZ DNS setup, run:

# samba-tool domain classicupgrade --dbdir=/usr/local/samba.PDC/dbdir/ --use-xattrs=yes --realm=samdom.example.com --dns-backend=BIND9_DLZ /usr/local/samba.PDC/etc/smb.PDC.conf

Parameter explanations:

--dbdir=                 Path to samba classic DC directory, containing all databases required for the migration
--use-xattrs=yes         Use the native filesystem capabilities for storing the neccessary extended attributes for Windows ACLs (required e. g. for the SysVol share)
--realm=                 Set the realm name
--dns-backend=           Optional. Required if BIND9_DLZ should be used as DNS backend. Default is the internal DNS (SAMBA_INTERNAL)

If you are having multiple NICs, classicupgrade auto-chooses the IPv4/v6 address of one NIC to setup the Domain Controller.
To prevent this, add the following to parameters the the classicupgrade command. This would bind Samba to the given
interface (eth0) and localhost (Samba should always listen on localhost, too).
--option="interfaces=lo eth0" --option="bind interfaces only=yes"

The following is a sample output of a successfull classicupgrade. Depending on your database backend, Samba version and other factors, the output will differ:

Reading smb.conf
Exporting account policy
Exporting groups
Exporting users
Next rid = 1007
Exporting posix attributes
Reading WINS database
Cannot open wins database, Ignoring: [Errno 2] No such file or directory: '/usr/local/samba.PDC/dbdir/wins.dat'
Looking up IPv4 addresses
Looking up IPv6 addresses
No IPv6 address will be assigned
Setting up share.ldb
Setting up secrets.ldb
Setting up the registry
Setting up the privileges database
Setting up idmap db
Setting up SAM db
Setting up sam.ldb partitions and settings
Setting up sam.ldb rootDSE
Pre-loading the Samba 4 and AD schema
Adding DomainDN: DC=samdom,DC=example,DC=com
Adding configuration container
Setting up sam.ldb schema
Setting up sam.ldb configuration data
Setting up display specifiers
Modifying display specifiers
Adding users container
Modifying users container
Adding computers container
Modifying computers container
Setting up sam.ldb data
Setting up well known security principals
Setting up sam.ldb users and groups
Setting up self join
Setting acl on sysvol skipped
Adding DNS accounts
Creating CN=MicrosoftDNS,CN=System,DC=samdom,DC=example,DC=com
Creating DomainDnsZones and ForestDnsZones partitions
Populating DomainDnsZones and ForestDnsZones partitions
See /usr/local/samba/private/named.conf for an example configuration include file for BIND
and /usr/local/samba/private/named.txt for further documentation required for secure DNS updates
Setting up sam.ldb rootDSE marking as synchronized
Fixing provision GUIDs
A Kerberos configuration suitable for Samba 4 has been generated at /usr/local/samba/private/krb5.conf
Setting up fake yp server settings
Once the above files are installed, your Samba4 server will be ready to use
Server Role:           active directory domain controller
Hostname:              DC1
NetBIOS Domain:        SAMDOM
DNS Domain:            samdom.example.com
DOMAIN SID:            S-1-5-21-4097619914-84555263-3210783664
Importing WINS database
Importing Account policy
Importing idmap database
Cannot open idmap database, Ignoring: [Errno 2] No such file or directory
Adding groups
Importing groups
Group already exists sid=S-1-5-21-4097619914-84555263-3210783664-513, groupname=Domain Users existing_groupname=Domain Users, Ignoring.
Commiting 'add groups' transaction to disk
Adding users
Importing users
Commiting 'add users' transaction to disk
Adding users to groups
Commiting 'add users to groups' transaction to disk
Setting password for administrator

Note: If you re-run the classicupgrade, you need to remove the auto-generated smb.conf and the databases:

# rm -f /usr/local/samba/etc/smb.conf
# rm -rf /usr/local/samba/private/*

After the classicupgrade

  • Disable the automatic start of your Samba PDC and LDAP server (if any).
  • Enable your Samba AD service to automatically start at boot time.
  • If your passdb backend was smbpasswd or tdbsam, you can remove the domain groups from /etc/group. All groups that had a groupmapping were imported, including their members.

Continuing with the AD DC setup

The „classicupdate“ process replaces the „provisioning“ step in the Samba AD DC HowTo. If you had finished the classicupgrade without problems, you have to continue with the Samba AD DC HowTo after the provisioning step.

Improving classicupgrade

Because of complexity and the various setups, the classicupgrade doesn't catch all exceptions with a meaningful message yet.

Please open a bug report for every uncaught exception error (please first search bugzilla, if it was already reported).

Of course all other bugs, feature enhancements, etc. should be reported, as well, to improve the migration process in future releases.

classicupgrade FAQ

What are the consequences changing an SID/RID?

Warning: Windows uses in it's backend only SIDs to identify users, groups and machines. Changing an SID without due consideration, may result in serious problems or damages!

Example 1: You have two accounts with the same SID. One of them is member of the local administrators group on a workstation. If you change the SID of this account, the group membership gets lost, because Windows had stored the account SID in the group and not the account name.

Example 2: You have two machine accounts with the same SID. If you change the SID of one account, then this computer is not part of the domain any more and logins are not possible. If you have duplicate SIDs and at least one of them is on a machine account, the easiest way is to delete the machine account and rejoin the computer to the domain.

Error: User 'Administrator' in your existing directory has SID ..., expected it to be ...-500

The error says what's wrong: In your NT4-style domain backend, the RID of the domain administrator account isn't -500, what it should be (see. Windows well-known security identifiers). Change it to 500 and start over. You can remove the account, too, as it will be automatically created during the AD provisioning. See: What are the consequences changing an SID/RID?

Not all attributes were copied when migrating from passwd backend = ldapsam

Sadly classicupdate currently does not migrate all attributes found in LDAP. You can follow bug report #9908 about the progress. But improvements would only take effect, when doing the classicupgrade - not afterwards!


  • Change the listen port of your NT4-style domain LDAP server to a different one than its default (389/tcp), if hosted on the same machine than your new Active Directory.
  • Write a small script, that walks through all user accounts in your AD, then search the same user account in your old LDAP and retrieve the attributes you want to transfer. Add them to an LDIF file, which can be imported with
# ldbmodify -H path/to/sam.ldb LDIFfilename