Difference between revisions of "Demoting a Samba AD DC"

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(Add information how to demote a dead, foreign DC (requires 4.4))
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= Demote a DC that isn't accessable any more=
 
= Demote a DC that isn't accessable any more=
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''Note: Samba versions prior 4.4 don't support demoting a foreign DC, that is offline. Upgrade your existing DCs to 4.4 or later, in that case.''
  
 
Follow this section, if your DC is not accessable any more, e. g. by hardware failure and it surely will never come back into the network.
 
Follow this section, if your DC is not accessable any more, e. g. by hardware failure and it surely will never come back into the network.
  
samba-tool currently does not support demote a foreign DC. That's why currently the only way to demote a lost DC is using the Windows tools. '''Sadly demoting e. g. through deleting the DC in ADUC, currently fails. See [https://bugzilla.samba.org/show_bug.cgi?id=10595 Bug report #10595].'''
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Run the following command on one of the remaining, working Domain Controller:
 
 
'''There are suspicion that samba DC with the metadate of the DC that isn't accessible ''would eat up memory and later trigger oom-killer.'''''
 
 
 
This information was correct Until 4.1.12, and the same problem might kill the 2nd and 3rd DC if you have.
 
  
Some people say that they can remove using the script below, but it was fully '''not tested'''.
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# samba-tool domain demote --remove-other-dead-server=DC2
Please use at your own risk.
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Removing nTDSConnection: CN=04baf417-eb41-4f31-a5f1-c739f0e92b1b,CN=NTDS Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com
[http://gallery.technet.microsoft.com/scriptcenter/d31f091f-2642-4ede-9f97-0e1cc4d577f3#content]
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Removing nTDSDSA: CN=NTDS Settings,CN=DC2,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com (and any children)
 +
Removing RID Set: CN=RID Set,CN=DC2,OU=Domain Controllers,DC=samdom,DC=example,DC=com
 +
Removing computer account: CN=DC2,OU=Domain Controllers,DC=samdom,DC=example,DC=com (and any child objects)
 +
Removing Samba-specific DNS service account: CN=dns-DC2,CN=Users,DC=samdom,DC=example,DC=com
 +
updating samdom.example.com keeping 3 values, removing 1 values
 +
updating DC=_kerberos._tcp.Default-First-Site-Name._sites,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
 +
updating DC=_ldap._tcp.Default-First-Site-Name._sites,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
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updating DC=_gc._tcp.Default-First-Site-Name._sites,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
 +
updating DC=_kerberos._tcp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
 +
updating DC=_kerberos._udp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
 +
updating DC=_kpasswd._tcp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
 +
updating DC=_kpasswd._udp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
 +
updating DC=_ldap._tcp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
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updating DC=_gc._tcp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
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updating DC=_ldap._tcp.4d5258b9-0cd7-4d78-bdd7-99ebe6b19751.domains,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
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updating DC=_kerberos._tcp.Default-First-Site-Name._sites.dc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
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updating DC=_ldap._tcp.Default-First-Site-Name._sites.dc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
 +
updating DC=_ldap._tcp.Default-First-Site-Name._sites.gc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
 +
updating DC=c14a774f-9732-4ec2-b9fa-2156c95c4e48,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 0 values, removing 1 values
 +
updating DC=_kerberos._tcp.dc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
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updating DC=_ldap._tcp.dc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
 +
updating DC=_ldap._tcp.gc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
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Removing Sysvol reference: CN=DC2,CN=Enterprise,CN=Microsoft System Volumes,CN=System,CN=Configuration,DC=samdom,DC=example,DC=com
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Removing Sysvol reference: CN=DC2,CN=samdom.example.com,CN=Microsoft System Volumes,CN=System,CN=Configuration,DC=samdom,DC=example,DC=com
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Removing Sysvol reference: CN=DC2,CN=Domain System Volumes (SYSVOL share),CN=File Replication Service,CN=System,DC=samdom,DC=example,DC=com
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Removing Sysvol reference: CN=DC2,CN=Topology,CN=Domain System Volume,CN=DFSR-GlobalSettings,CN=System,DC=samdom,DC=example,DC=com
  
  

Revision as of 17:44, 29 February 2016

Introduction

Whenever a Domain Controller needs to be removed from your domain, for what ever reason, you will have to demote it. This HowTo describes different scenarios to demote a Domain Controller.



Server information used in this HowTo

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

Installation directory:                 /usr/local/samba/
DC to demote:                           DC2
Different DC remaining in the network:  DC1
DNS Domain Name/Realm:                  samdom.example.com
NT4 Domain Name:                        samdom



Demote a still working Domain Controller

Follow this section, if your DC is accessable and working.

  • Log into the DC you want to demote.
  • Verify that the DC is not the last one remaining in the domain!
  • Make sure, that this DC does not contain any FSMO role:
# samba-tool fsmo show
InfrastructureMasterRole owner: CN=NTDS Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com
RidAllocationMasterRole owner: CN=NTDS Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com
PdcEmulationMasterRole owner: CN=NTDS Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com
DomainNamingMasterRole owner: CN=NTDS Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com
SchemaMasterRole owner: CN=NTDS Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com
  • If you are using Samba 4.3.0 and up, the samba tool command will show an extra two FSMO roles:
DomainDnsZonesMasterRole owner: CN=NTDS Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com
ForestDnsZonesMasterRole owner: CN=NTDS Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com

Irrespective of version, there are 7 FSMO roles, see show fsmo roles for how to display all 7 roles on earlier versions.

If it still contains one or more FSMO roles, transfer them to a different DC.
  • Demote the DC:
# samba-tool domain demote -Uadministrator
Using DC1.samdom.example.com as partner server for the demotion
Password for [SAMDOM\administrator]:
Desactivating inbound replication
Asking partner server DC1.samdom.example.com to synchronize from us
Changing userControl and container
Demote successfull
  • Shutdown Samba



Demote a DC that isn't accessable any more

Note: Samba versions prior 4.4 don't support demoting a foreign DC, that is offline. Upgrade your existing DCs to 4.4 or later, in that case.

Follow this section, if your DC is not accessable any more, e. g. by hardware failure and it surely will never come back into the network.

Run the following command on one of the remaining, working Domain Controller:

# samba-tool domain demote --remove-other-dead-server=DC2
Removing nTDSConnection: CN=04baf417-eb41-4f31-a5f1-c739f0e92b1b,CN=NTDS Settings,CN=DC1,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com
Removing nTDSDSA: CN=NTDS Settings,CN=DC2,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samdom,DC=example,DC=com (and any children)
Removing RID Set: CN=RID Set,CN=DC2,OU=Domain Controllers,DC=samdom,DC=example,DC=com
Removing computer account: CN=DC2,OU=Domain Controllers,DC=samdom,DC=example,DC=com (and any child objects)
Removing Samba-specific DNS service account: CN=dns-DC2,CN=Users,DC=samdom,DC=example,DC=com
updating samdom.example.com keeping 3 values, removing 1 values
updating DC=_kerberos._tcp.Default-First-Site-Name._sites,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_ldap._tcp.Default-First-Site-Name._sites,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_gc._tcp.Default-First-Site-Name._sites,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_kerberos._tcp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_kerberos._udp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_kpasswd._tcp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_kpasswd._udp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_ldap._tcp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_gc._tcp,DC=samdom.example.com,CN=MicrosoftDNS,DC=DomainDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_ldap._tcp.4d5258b9-0cd7-4d78-bdd7-99ebe6b19751.domains,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_kerberos._tcp.Default-First-Site-Name._sites.dc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_ldap._tcp.Default-First-Site-Name._sites.dc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_ldap._tcp.Default-First-Site-Name._sites.gc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=c14a774f-9732-4ec2-b9fa-2156c95c4e48,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 0 values, removing 1 values
updating DC=_kerberos._tcp.dc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_ldap._tcp.dc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
updating DC=_ldap._tcp.gc,DC=_msdcs.samdom.example.com,CN=MicrosoftDNS,DC=ForestDnsZones,DC=samdom,DC=example,DC=com keeping 1 values, removing 1 values
Removing Sysvol reference: CN=DC2,CN=Enterprise,CN=Microsoft System Volumes,CN=System,CN=Configuration,DC=samdom,DC=example,DC=com
Removing Sysvol reference: CN=DC2,CN=samdom.example.com,CN=Microsoft System Volumes,CN=System,CN=Configuration,DC=samdom,DC=example,DC=com
Removing Sysvol reference: CN=DC2,CN=Domain System Volumes (SYSVOL share),CN=File Replication Service,CN=System,DC=samdom,DC=example,DC=com
Removing Sysvol reference: CN=DC2,CN=Topology,CN=Domain System Volume,CN=DFSR-GlobalSettings,CN=System,DC=samdom,DC=example,DC=com



Verifying that nothing was left

The following steps are done on a Windows computer having RSAT installed.

Warning: The following are just cleanup steps, if something was left after a demote! It's not a replacement for the demote process itself!

  • Open „Active Directory Users and Computers“
  • Go to the container „Domain Controllers“ and verify that the demoted DC was removed. If not, remove the account manually. This would also cleanup metadata. DC removal via ADUC is currently broken. See Bug report #10595.
ADUC Domain Controllers.png
  • Open „Active Directory Sites and Services“
  • Check that the demoted DC doesn't exist any more in any site. If an entry is still there, remove it manually.
ADSS Domain Controllers.png
  • Open the „DNS“ console
  • Check in all zones, that no entry about the demoted DC is still existing.
DNS Domain Controllers.png