Difference between revisions of "Migrating a Samba NT4 Domain to Samba AD (Classic Upgrade)"

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=== Prevent failure due to duplicate SID's ===
=== Prevent failure due to duplicate SID's ===
A common problem is duplicate SID's in the backend. In a healthy environment, a [https://en.wikipedia.org/wiki/Security_Identifier SID] is unique. But old Samba versions without sanity checks, wrong manual changes or other things, could have lead to duplicate SID's in your environment. These need to be fixed/removed. Otherwise the classicupgrade is not possible!
A common problem is duplicate SID's in the backend. In a healthy environment, a [https://en.wikipedia.org/wiki/Security_Identifier SID] is unique. However, old Samba versions without sanity checks, wrong manual changes or other things, could have allowed duplicate SID's in your environment. These need to be fixed/removed. Otherwise the classicupgrade is not possible!
If any of your users have a RID less than '1000' and you wish these to exist in the new AD domain, you will need to change their RID, see below for how to do this.
If any of your users have a RID less than '1000' and you wish them to exist in the new AD domain, you will need to change their RID, see below for how to do this.
See: [[#What_are_the_consequences_of_changing_a_SID.2FRID.3F|What are the consequences changing an SID/RID?]]
See: [[#What_are_the_consequences_of_changing_a_SID.2FRID.3F|What are the consequences changing an SID/RID?]]

Revision as of 08:03, 10 May 2018


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 scenario. 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 one way! This means that once your clients contact your migrated AD Domain Controller, they will never be able to access the NT4-style domain again - even if you roll back your changes!

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

It used to be thought that using Windows RIDs for Unix IDs was acceptable, time has proven otherwise. If you have users and groups that use their Windows RID for their Unix ID (uidNumber or gidNumber), you should consider changing these before carrying out the upgrade. You should also consider removing any Unix IDs (uidNumber or gidNumber) from the 'Well known SIDs', except for the 'Domain Users' group.

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 have the choice of:

  • allowing the LDAP backend to 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. In this case, make sure that you check/adapt your configuration (ldap.conf, smb.conf) to retrieve the information from your old LDAP backend host.
  • install a temporary 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 failure due to duplicate SID's

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

If any of your users have a RID less than '1000' and you wish them to exist in the new AD domain, you will need to change their RID, see below for how to do this.

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

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

# A quick and dirty python script that checks for duplicate 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 SID's 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 SID's 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"
Successfully 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 failure due to common user/group names

If you have any usernames that are the same as a groupname, you will 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 be 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 adding

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 DNS best practice.

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

Domain Controller name

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

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 Operating System 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, If you are carrying out the upgrade on the same server as your NT4-style domain PDC, you should shutdown your Samba PDC services (smbd, nmbd, winbind), but leave your LDAP server running (if using passwd backend = ldapsam). If you are carrying out the upgrade on a new Computer, you should also stop any running Samba services.

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 that could happen, if 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 will 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 will get permission denied errors!

To start the classicupgrade with Internal DNS setup, run:

# samba-tool domain classicupgrade --dbdir=/usr/local/samba.PDC/dbdir/ \
--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/ \
--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
--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 have multiple NICs, classicupgrade auto-chooses the IPv4/v6 address of one NIC to setup 
the Domain Controller.
To prevent this, add the following parameters to the classicupgrade command. This will 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 successful 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 will 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 services and LDAP server (if any).
  • Enable your Samba AD service to automatically start at boot time.
  • If your passdb backend was smbpasswd or tdbsam, remove the domain groups from /etc/group. All groups that had a groupmapping were imported, including their members. You should also remove any Samba users from /etc/passwd, they are now stored in AD.

Continuing with the AD DC setup

The „classicupdate“ process replaces the „provisioning“ step in the Samba AD DC HowTo. If the classicupgrade finished 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, to see if it has already been 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 of changing a SID/RID?

Warning: SID's are the only thing that Windows uses in it's backend to identify users, groups and machines. Changing a 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 SID's 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 of changing a 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 as 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