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Getting Started with Group Managed Service Accounts

Published: May 17, 2012

Updated: October 17, 2012

Applies To: Windows Server 2012, Windows Server 2012 R2



This guide provides step-by-step instructions and background information for enabling and using group Managed Service Accounts in Windows Server 2012.

In this document

noteNote
This topic includes sample Windows PowerShell cmdlets that you can use to automate some of the procedures described. For more information, see Using Cmdlets.

When a client computer connects to a service which is hosted on a server farm using network load balancing (NLB) or some other method where all the servers appear to be the same service to the client, then authentication protocols supporting mutual authentication such as Kerberos cannot be used unless all the instances of the services use the same principal. This means that each service has to use the same passwords/keys to prove their identity.

noteNote
Failover clusters do not support gMSAs. However, services that run on top of the Cluster service can use a gMSA or a sMSA if they are a Windows service, an App pool, a scheduled task, or natively support gMSA or sMSA.

Services have the following principals from which to choose, and each has certain limitations.

 

Principals Scope Services supported Password management

Computer Account of Windows system

Domain

Limited to one domain joined server

Computer manages

Computer Account without Windows system

Domain

Any domain joined server

None

Virtual Account

Local

Limited to one server

Computer manages

Windows 7 standalone Managed Service Account

Domain

Limited to one domain joined server

Computer manages

User Account

Domain

Any domain joined server

None

Group Managed Service Account

Domain

Any Windows Server 2012 domain-joined server

The domain controller manages, and the host retrieves

A Windows computer account, or a Windows 7 standalone Managed Service Account (sMSA), or virtual accounts cannot be shared across multiple systems. If you configure one account for services on server farms to share, you would have to choose a user account or a computer account apart from a Windows system. Either way, these accounts do not have the capability of single-point-of-control password management. This creates problem where each organization needs to create an expensive solution to update keys for the service in Active Directory and then distribute the keys to all instances of those services.

With Windows Server 2012, services or service administrators do not need to manage password synchronization between service instances when using group Managed Service Accounts (gMSA). You provision the gMSA in AD and then configure the service which supports Managed Service Accounts. You can provision a gMSA using the *-ADServiceAccount cmdlets which are part of the Active Directory module. Service identity configuration on the host is supported by:

  • Same APIs as sMSA, so products which support sMSA will support gMSA

  • Services which use Service Control Manager to configure logon identity

  • Services which use the IIS manager for application pools to configure identity

  • Tasks using Task Scheduler.

For more information about standalone Managed Service Accounts, see Managed Service Accounts. For more information about group Managed Service Accounts, see Group Managed Service Accounts Overview.

The following table lists the operating system requirements for Kerberos authentication to work with services using gMSA. The Active Directory requirements are listed after the table.

A 64-bit architecture is required to run the Windows PowerShell commands used to administer group Managed Service Accounts.

Operating system requirements

 

Element Requirement Operating system

Client Application host

RFC compliant Kerberos client

At least Windows XP

User account’s domain DCs

RFC compliant KDC

At least Windows Server 2003

Shared service member hosts

Windows Server 2012

Member host’s domain DCs

RFC compliant KDC

At least Windows Server 2003

gMSA account’s domain DCs

Windows Server 2012 DCs available for host to retrieve the password

Domain with Windows Server 2012 which can have some systems earlier than Windows Server 2012

Backend service host

RFC compliant Kerberos application server

At least Windows Server 2003

Backend service account’s domain DCs

RFC compliant KDC

At least Windows Server 2003

Windows PowerShell for Active Directory

Windows PowerShell for Active Directory installed locally on a computer supporting a 64-bit architecture or on your remote management computer (for example, using the Remote Server Administration Toolkit)

Windows Server 2012

Active Directory Domain Service requirements

  • The Active Directory schema in the gMSA domain’s forest needs to be updated to Windows Server 2012 to create a gMSA.

    You can update the schema by installing a domain controller that runs Windows Server 2012 or by running the version of adprep.exe from a computer running Windows Server 2012. The object-version attribute value for the object CN=Schema,CN=Configuration,DC=Contoso,DC=Com must be 52.

  • New gMSA account provisioned

  • If you are managing the service host permission to use gMSA by group, then new or existing security group

  • If managing service access control by group, then new or existing security group

  • If the first master root key for Active Directory is not deployed in the domain or has not been created, then create it. The result of its creation can be verified in the KdsSvc Operational log, Event ID 4004.

For instructions how to create the key, see Create the Key Distribution Services KDS Root Key. Microsoft Key Distribution Service (kdssvc.dll) the root key for AD.

Lifecycle

The lifecycle of a server farm using the gMSA feature typically involves the following tasks:

  • Deploying a new server farm

  • Adding member hosts to an existing server farm

  • Decommissioning member hosts from an existing server farm

  • Decommissioning an existing server farm

  • Removing a compromised member host from a server farm if required.

When deploying a new server farm, the service administrator will need to determine:

  • If the service supports using gMSAs

  • If the service requires inbound or outbound authenticated connections

  • The computer account names for the member hosts for the service using the gMSA

  • The NetBIOS name for the service

  • The DNS host name for the service

  • The Service Principal Names (SPNs) for the service

  • The password change interval (default is 30 days).

You can create a gMSA only if the forest schema has been updated to Windows Server 2012, the master root key for Active Directory has been deployed, and there is at least one Windows Server 2012 DC in the domain in which the gMSA will be created.

Membership in Domain Admins, Account Operators or ability to create msDS-GroupManagedServiceAccount objects, is the minimum required to complete the following procedures. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.

  1. On the Windows Server 2012 domain controller, run Windows PowerShell from the Taskbar.

  2. At the command prompt for the Windows PowerShell, type the following commands, and then press ENTER. (The Active Directory module will load automatically.)

    New-ADServiceAccount [-Name] <string> -DNSHostName <string> [-KerberosEncryptionType <ADKerberosEncryptionType>] [-ManagedPasswordIntervalInDays <Nullable[Int32]>] [-PrincipalsAllowedToRetrieveManagedPassword <ADPrincipal[]>] -SamAccountName <string> -ServicePrincipalNames <string[]>

     

    Parameter String Example

    Name

    Name of the account

    ITFarm1

    DNSHostName

    DNS host name of service

    ITFarm1.contoso.com

    KerberosEncryptionType

    Any encryption types supported by the host servers

    RC4, AES128, AES256

    ManagedPasswordIntervalInDays

    Password change interval in days (default is 30 days if not provided)

    90

    PrincipalsAllowedToRetrieveManagedPassword

    The computer accounts of the member hosts or the security group that the member hosts are a member of

    ITFarmHosts

    SamAccountName

    NetBIOS name for the service if not same as Name

    ITFarm1

    ServicePrincipalNames

    Service Principal Names (SPNs) for the service

    http/ITFarm1.contoso.com/contoso.com, http/ITFarm1.contoso.com/contoso, http/ITFarm1/contoso.com, http/ITFarm1/contoso

    ImportantImportant
    The password change interval can only be set during creation. If you need to change the interval, you must create a new gMSA and set it at creation time.

    Example

    Enter the command on a single line, even though they might appear word-wrapped across several lines here because of formatting constraints.

    New-ADServiceAccount ITFarm1 -DNSHostName ITFarm1.contoso.com -PrincipalsAllowedToRetrieveManagedPassword ITFarmHosts -KerberosEncryptionType RC4, AES128, AES256 -ServicePrincipalNames http/ITFarm1.contoso.com/contoso.com, http/ITFarm1.contoso.com/contoso, http/ITFarm1/contoso.com, http/ITFarm1/contoso 
    
    

Membership in Domain Admins, Account Operators, or ability to create msDS-GroupManagedServiceAccount objects, is the minimum required to complete this procedure. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.

  1. On the Windows Server 2012 domain controller, run Windows PowerShell from the Taskbar.

  2. At the command prompt for the Windows PowerShell Active Directory module, type the following commands, and then press ENTER:

    New-ADServiceAccount [-Name] <string> -RestrictToOutboundAuthenticationOnly [-ManagedPasswordIntervalInDays <Nullable[Int32]>] [-PrincipalsAllowedToRetrieveManagedPassword <ADPrincipal[]>]

     

    Parameter String Example

    Name

    Name the account

    ITFarm1

    ManagedPasswordIntervalInDays

    Password change interval in days (default is 30 days if not provided)

    75

    PrincipalsAllowedToRetrieveManagedPassword

    The computer accounts of the member hosts or the security group that the member hosts are a member of

    ITFarmHosts

    ImportantImportant
    The password change interval can only be set during creation. If you need to change the interval, you must create a new gMSA and set it at creation time.

Example

New-ADServiceAccount ITFarm1 -RestrictToOutboundAuthenticationOnly - PrincipalsAllowedToRetrieveManagedPassword ITFarmHosts 

To configure the services in Windows Server 2012, see the following feature documentation:

Other services could support gMSA. See the appropriate product documentation for details on how to configure those services.

If using security groups for managing member hosts, add the computer account for the new member host to the security group (that the gMSA’s member hosts are a member of) using one of the following methods.

Membership in Domain Admins, or the ability to add members to the security group object, is the minimum required to complete these procedures. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.

If using computer accounts, find the existing accounts and then add the new computer account.

Membership in Domain Admins, Account Operators, or ability to manage msDS-GroupManagedServiceAccount objects, is the minimum required to complete this procedure. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.

  1. On the Windows Server 2012 domain controller, run Windows PowerShell from the Taskbar.

  2. At the command prompt for the Windows PowerShell Active Directory module, type the following commands, and then press ENTER:

    Get-ADServiceAccount [-Name] <string> -PrincipalsAllowedToRetrieveManagedPassword

  3. At the command prompt for the Windows PowerShell Active Directory module, type the following commands, and then press ENTER:

    Set-ADServiceAccount [-Name] <string> -PrincipalsAllowedToRetrieveManagedPassword <ADPrincipal[]>

 

Parameter String Example

Name

Name the account

ITFarm1

PrincipalsAllowedToRetrieveManagedPassword

The computer accounts of the member hosts or the security group that the member hosts are a member of

Host1, Host2, Host3

Example

For example, to add member hosts type the following commands, and then press ENTER.

Get-ADServiceAccount [-Name] ITFarm1 -PrincipalsAllowedToRetrieveManagedPassword

Set-ADServiceAccount [-Name] ITFarm1-PrincipalsAllowedToRetrieveManagedPassword Host1 Host2 Host3

Membership in Domain Admins, Account Operators, or the ability to write to msDS-GroupManagedServiceAccount objects, is the minimum required to complete these procedures. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.

Open the Active Directory Module for Windows PowerShell, and set any property by using the Set-ADServiceAccount cmdlet.

For detailed information how to set these properties, see Set-ADServiceAccount in the TechNet Library or by typing Get-Help Set-ADServiceAccount at the Active Directory module for Windows PowerShell command prompt and pressing ENTER.

Membership in Domain Admins, or ability to remove members from the security group object, is the minimum required to complete these procedures. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.

If using security groups for managing member hosts, remove the computer account for the decommissioned member host from the security group that the gMSA’s member hosts are a member of using either of the following methods.

If listing computer accounts, retrieve the existing accounts and then add all but the removed computer account.

Membership in Domain Admins, Account Operators, or ability to manage msDS-GroupManagedServiceAccount objects, is the minimum required to complete this procedure. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.

  1. On the Windows Server 2012 domain controller, run Windows PowerShell from the Taskbar.

  2. At the command prompt for the Windows PowerShell Active Directory module, type the following commands, and then press ENTER:

    Get-ADServiceAccount [-Name] <string> -PrincipalsAllowedToRetrieveManagedPassword

  3. At the command prompt for the Windows PowerShell Active Directory module, type the following commands, and then press ENTER:

    Set-ADServiceAccount [-Name] <string> -PrincipalsAllowedToRetrieveManagedPassword <ADPrincipal[]>

 

Parameter String Example

Name

Name the account

ITFarm1

PrincipalsAllowedToRetrieveManagedPassword

The computer accounts of the member hosts or the security group that the member hosts are a member of

Host1, Host3

Example

For example, to remove member hosts type the following commands, and then press ENTER.

Get-ADServiceAccount [-Name] ITFarm1 -PrincipalsAllowedToRetrieveManagedPassword

Set-ADServiceAccount [-Name] ITFarm1 -PrincipalsAllowedToRetrieveManagedPassword Host1 Host3

Remove the cached gMSA credentials from the member host using Uninstall-ADServiceAccount or the NetRemoveServiceAccount API on the host system.

Membership in Administrators, or equivalent, is the minimum required to complete these procedures. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.

  1. On the Windows Server 2012 domain controller, run Windows PowerShell from the Taskbar.

  2. At the command prompt for the Windows PowerShell Active Directory module, type the following commands, and then press ENTER:

    Uninstall-ADServiceAccount < ADServiceAccount>

    Example

    For example, to remove the cached credentials for a gMSA named ITFarm1 type the following command, and then press ENTER:

    Uninstall-ADServiceAccount ITFarm1
    

For more information about the Uninstall-ADServiceAccount cmdlet, at the Active Directory module for Windows PowerShell command prompt, type Get-Help Uninstall-ADServiceAccount, and then press ENTER, or see the information on the TechNet web at Uninstall-ADServiceAccount.

When decommissioning an existing server farm, you should remove the following objects from AD:

  • If the gMSA is the only member, the security group that the gMSA is a member of which is used for access control

  • If the security group is only used for member hosts, the security group that the member hosts are a member of

  • gMSA.

To delete a security group, use Active Directory Users and Computers, dsrm or Remove-ADGroup. To delete a gMSA, use Active Directory Users and Computers or Remove-ADServiceAccount.

Membership in Domain Admins, Account Operators, or ability to delete msDS-GroupManagedServiceAccount and security group objects, is the minimum required to complete these procedures. For detailed information about using the appropriate accounts and group memberships, see Local and Domain Default Groups.

  1. On the Windows Server 2012 domain controller, run Windows PowerShell from the Taskbar.

  2. At the command prompt for the Windows PowerShell Active Directory module, type the following commands, and then press ENTER:

    Remove-ADServiceAccount < ADServiceAccount>

    Example

    For example, to delete a gMSA named ITFarm1 type the following command, and then press ENTER:

    Remove-ADServiceAccount ITFarm1 
    
    

For more information about the Remove-ADServiceAccount cmdlet, at the Active Directory module for Windows PowerShell command prompt, type Get-Help Remove-ADServiceAccount, and then press ENTER, or see the information on the TechNet web at Remove-ADServiceAccount.

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