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7.2. Integration

Integrating Red Hat Gluster Storage Servers into an Active Directory domain involves the following series of steps:
  1. Configure Authentication
  2. Join Active Directory Domain
  3. Verify/Test Active Directory and Services

7.2.1. Configure Authentication

In order to join a cluster to the Active Directory domain, a couple of files have to be edited manually on all nodes.

Note

  • Ensure that CTDB is configured before the active directory join. For more information see, Section 6.3.1 Setting up CTDB for Samba in the Red Hat Gluster Storage Administration Guide.
  • It is recommended to take backups of the configuration and of Samba’s databases (local and ctdb) before making any changes.

7.2.1.1. Basic Samba Configuration

As of Red Hat Gluster Storage 3.4 Batch 4 Update, the recommended idmap configuration method for new deployments is autorid. Red Hat recommends autorid because in addition to automatically calculating user and group identifiers like tdb, it performs fewer database transactions and read operations, and is a prerequisite for supporting secure ID history (SID history).

Warning

Do not change the idmap configuration in existing deployments. Doing so requires a large number of changes, such as modifying the permissions and access control lists of all files in the shared file system, which unless done carefully can create user access problems. If you do need to change the idmap configuration settings for an existing deployment, contact Red Hat support for assistance.
The Samba configuration file /etc/samba/smb.conf must be identical on all nodes, and must contain the relevant parameters for AD. Along with that, a few other settings are required in order to activate mapping of user and group IDs.
The following example depicts the minimal Samba configuration for AD integration: 
[global]
netbios name = RHS-SMB
workgroup = ADDOM
realm = addom.example.com
security = ads
clustering = yes
idmap config * : backend = autorid
idmap config * : range = 1000000-19999999
idmap config * : rangesize = 1000000

# -----------------RHS Options -------------------------
#
# The following line includes RHS-specific configuration options. Be careful with this line.

       include = /etc/samba/rhs-samba.conf

#=================Share Definitions =====================

Warning

The example above is the complete global section required in the smb.conf file. Ensure that nothing else appears in this section in order to prevent gluster mechanisms from changing settings when starting or stopping the ctdb lock volume.
The netbios name consists of only one name which has to be the same name on all cluster nodes. Windows clients will only access the cluster via that name (either in this short form or as an FQDN). The individual node hostname (rhs-srv1, rhs-srv2, …) must not be used for the netbios name parameter.

Note

  • The idmap range defines the lowerst and hightest identifier numbers that can be used. Specify a range large enough to cover the number of objects specified in rangesize.
  • The idmap rangesize specifies the number of identifiers available for each domain range. In this case there are one million identifiers per domain range, and the range parameter indicates that there are nearly 19 million identifiers total, meaning that there are a total of 19 possible domain ranges.
  • If you want to be able to use the individual host names to also access specific nodes, you can add them to the netbios aliases parameter of smb.conf.
  • In an AD environment, it is usually not required to run nmbd. However, if you have to run nmbd, then make sure to set the cluster addresses smb.conf option to the list of public IP addresses of the cluster.

7.2.1.2. Alternative Configuration using ad backend

If you need full control over Active Directory IDs, you can adapt the Samba configuration further by using the idmap_ad module in addition to autorid. The idmap_ad module reads the unix IDs from the AD's special unix attributes. This has to be configured by the AD domain's administrator before it can be used by Samba and winbind.
In order for Samba to use idmap_ad, the AD domain admin has to prepare the AD domain for using the so called unix extensions and assign unix IDs to all users and groups that should be able to access the Samba server.
For example, following is an extended Samba configuration file to use the idmap_ad backend for the ADDOM domain. The default autorid backend catches all objects from domains other than the ADDOM domain. 
[global]
netbios name = RHS-SMB
workgroup = ADDOM
realm = addom.example.com
security = ads
clustering = yes
idmap config * : backend = autorid
idmap config * : range = 1000000-1999999
idmap config ADDOM : backend = ad
idmap config ADDOM : range = 3000000-3999999
idmap config ADDOM : schema mode = rfc2307
winbind nss info = rfc2307

# -------------------RHS Options -------------------------------
#
# The following line includes RHS-specific configuration options. Be careful with this line.

       include = /etc/samba/rhs-samba.conf

#===================Share Definitions =========================

Note

  • The range for the idmap_ad configuration is prescribed by the AD configuration. This has to be obtained by AD administrator.
  • Ranges for different idmap configurations must not overlap.
  • The schema mode and the winbind nss info setting should have the same value. If the domain is at level 2003R2 or newer, then rfc2307 is the correct value. For older domains, additional values sfu and sfu20 are available. See the manual pages of idmap_ad and smb.conf for further details.

7.2.1.3. Verifying the Samba Configuration

Test the new configuration file using the testparm command. For example: 
# testparm -s
Load smb config files from /etc/samba/smb.conf
rlimit_max: increasing rlimit_max (1024) to minimum Windows limit (16384)
Loaded services file OK.

Server role: ROLE_DOMAIN_MEMBER

# Global parameters
[global]
    workgroup = ADDOM
    realm = addom.example.com
    netbios name = RHS-SMB
    security = ADS
    clustering = Yes
    winbind nss info = rfc2307
    idmap config addom : schema mode = rfc2307
    idmap config addom : range = 3000000-3999999
    idmap config addom : backend = ad
    idmap config * : range = 1000000-1999999
    idmap config * : backend = autorid

7.2.1.4. nsswitch Configuration

Once the Samba configuration has been made, Samba has to be enabled to use the mapped users and groups from AD. This is achieved via the local Name Service Switch (NSS) that has to be made aware of the winbind. To use the winbind NSS module, edit the /etc/nsswitch.conf file. Make sure the file contains the winbind entries for the passwd and group databases. For example: 
...
passwd: files winbind
group: files winbind
...
This will enable the use of winbind and should make users and groups visible on the individual cluster node once Samba is joined to AD and winbind is started.

7.2.2. Join Active Directory Domain

Prior to joining AD, CTDB must be started so that the machine account information can be stored in a database file that is available on all cluster nodes via CTDB. In addition to that, all other Samba services should be stopped. If key-based SSH authentication without a password has been configured for the root user between the nodes, you can use the onnode tool to run these commands on all nodes from a single node:
For RHEL 7 and RHEL 8, run: 
# onnode all systemctl start ctdb
# onnode all systemctl stop winbind
# onnode all systemctl stop smb
For RHEL 6, run: 
# onnode all service ctdb start
# onnode all service winbind stop
# onnode all service smb stop

Note

  • If your configuration has CTDB managing Winbind and Samba, they can be temporarily disabled with the following commands (to be executed prior to the above stop commands) so as to prevent CTDB going into an unhealthy state when they are shut down: 
    # onnode all ctdb event script disable legacy 49.winbind
# onnode all ctdb event script disable legacy 50.samba
  • For some versions of Red Hat Gluster Storage, a bug in the selinux policy prevents 'ctdb disablescript SCRIPT' from succeeding. If this is the case, 'chmod -x /etc/ctdb/events.d/SCRIPT' can be executed as a workaround from a root shell.
  • Shutting down winbind and smb is primarily to prevent access to SMB services during this AD integration. These services may be left running but access to them should be prevented through some other means.
The join is initiated via the net utility from a single node:

Warning

The following step must be executed only on one cluster node and should not be repeated on other cluster nodes. CTDB makes sure that the whole cluster is joined by this step. 
# net ads join -U Administrator
Enter Administrator's password:
Using short domain name -- ADDOM
Joined 'RHS-SMB' to dns domain addom.example.com'
Not doing automatic DNS update in a clustered setup.
Once the join is successful, the cluster ip addresses and the cluster netbios name should be made public in the network. For registering multiple public cluster IP addresses in the AD DNS server, the net utility can be used again: 
# net ads dns register rhs-smb <PUBLIC IP 1> <PUBLIC IP 2> ...
This command will make sure the DNS name rhs-smb will resolve to the given public IP addresses. The DNS registrations use the cluster machine account for authentication in AD, which means this operation only can be done after the join has succeeded.
Registering the NetBIOS name of the cluster is done by the nmbd service. In order to make sure that the nmbd instances on the hosts don’t overwrite each other’s registrations, the ‘cluster addresses’ smb.conf option should be set to the list of public addresses of the whole cluster.

7.2.3. Verify/Test Active Directory and Services

When the join is successful, the Samba and the Winbind daemons can be started.
Start nmdb, winbind and smb services using the following commands:
For RHEL 7 and RHEL 8, run: 
# onnode all systemctl start nmb
# onnode all systemctl start winbind
# onnode all systemctl start smb
For RHEL 6, run: 
# onnode all service nmb start
# onnode all service winbind start
# onnode all service smb start

Note

  • If you previously disabled CTDB’s ability to manage Winbind and Samba they can be re-enabled with the following commands: 
    # onnode all ctdb event script enable legacy 50.samba
# onnode all ctdb event script enable legacy 49.winbind
  • With the latest ctdb-4.9.8-105.el7rhgs.x86_64 package, the paths of ctdb managed service scripts have changed. The script files are now available under /etc/ctdb/events/legacy/ after enabling them from /usr/share/ctdb/events/legacy.
  • To enable ctdb event script, execute the following command: 
    ctdb event script enable legacy 49.winbind
  • To enable ctbd event script on all nodes, execute the following command: 
    # onnode all ctdb event script enable legacy 49.winbind
Execute the following verification steps:
  1. Verify the join by executing the following steps

    Verify the join to check if the created machine account can be used to authenticate to the AD LDAP server using the following command: 
    # net ads testjoin
Join is OK
  2. Execute the following command to display the machine account’s LDAP object 
    # net ads status -P
objectClass: top
objectClass: person
objectClass: organizationalPerson
objectClass: user
objectClass: computer
cn: rhs-smb
distinguishedName: CN=rhs-smb,CN=Computers,DC=addom,DC=example,DC=com
instanceType: 4
whenCreated: 20150922013713.0Z
whenChanged: 20151126111120.0Z
displayName: RHS-SMB$
uSNCreated: 221763
uSNChanged: 324438
name: rhs-smb
objectGUID: a178177e-4aa4-4abc-9079-d1577e137723
userAccountControl: 69632
badPwdCount: 0
codePage: 0
countryCode: 0
badPasswordTime: 130880426605312806
lastLogoff: 0
lastLogon: 130930100623392945
localPolicyFlags: 0
pwdLastSet: 130930098809021309
primaryGroupID: 515
objectSid: S-1-5-21-2562125317-1564930587-1029132327-1196
accountExpires: 9223372036854775807
logonCount: 1821
sAMAccountName: rhs-smb$
sAMAccountType: 805306369
dNSHostName: rhs-smb.addom.example.com
servicePrincipalName: HOST/rhs-smb.addom.example.com
servicePrincipalName: HOST/RHS-SMB
objectCategory: CN=Computer,CN=Schema,CN=Configuration,DC=addom,DC=example,DC=com
isCriticalSystemObject: FALSE
dSCorePropagationData: 16010101000000.0Z
lastLogonTimestamp: 130929563322279307
msDS-SupportedEncryptionTypes: 31
  3. Execute the following command to display general information about the AD server: 
    # net ads info
LDAP server: 10.11.12.1
LDAP server name: dc1.addom.example.com
Realm: ADDOM.EXAMPLE.COM
Bind Path: dc=ADDOM,dc=EXAMPLE,dc=COM
LDAP port: 389
Server time: Thu, 26 Nov 2015 11:15:04 UTC
KDC server: 10.11.12.1
Server time offset: -26
  4. Verify if winbind is operating correctly by executing the following steps

    Execute the following command to verify if winbindd can use the machine account for authentication to AD 
    # wbinfo -t
checking the trust secret for domain ADDOM via RPC calls succeeded
  5. Execute the following command to resolve the given name to a Windows SID 
    # wbinfo --name-to-sid 'ADDOM\Administrator'
S-1-5-21-2562125317-1564930587-1029132327-500 SID_USER (1)
  6. Execute the following command to verify authentication: 
    # wbinfo -a 'ADDOM\user'
Enter ADDOM\user's password:
plaintext password authentication succeeded
Enter ADDOM\user's password:
challenge/response password authentication succeeded
    or, 
    # wbinfo -a 'ADDOM\user%password'
plaintext password authentication succeeded
challenge/response password authentication succeeded
  7. Execute the following command to verify if the id-mapping is working properly: 
    # wbinfo --sid-to-uid <SID-OF-ADMIN>
1000000
  8. Execute the following command to verify if the winbind Name Service Switch module works correctly: 
    # getent passwd 'ADDOM\Administrator'
ADDOM\administrator:*:1000000:1000004::/home/ADDOM/administrator:/bin/false
  9. Execute the following command to verify if samba can use winbind and the NSS module correctly: 
    # smbclient -L rhs-smb -U 'ADDOM\Administrator'
Domain=[ADDOM] OS=[Windows 6.1] Server=[Samba 4.2.4]

        Sharename       Type      Comment
        ---------       ----      -------
        IPC$            IPC       IPC Service (Samba 4.2.4)
Domain=[ADDOM] OS=[Windows 6.1] Server=[Samba 4.2.4]

        Server               Comment
        ---------            -------
        RHS-SMB         Samba 4.2.4

        Workgroup            Master
        ---------            -------
        ADDOM             RHS-SMB
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