CentOS Stream 8
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FreeIPA : trust Active Directory
Configure Cross Forest Trust between FreeIPA domain and Windows Active Directory domain.
This example is based on the environment like follows.
Domain Server : CentOS Stream 8 Windows Server 2019
NetBIOS Name : IPA01 FD3S01
Domain Name : ipa.srv.world ad.srv.world
Host Name : dlp.ipa.srv.world fd3s.ad.srv.world
+----------------------+          |           +----------------------+
| [ FreeIPA (CentOS) ] | ||  [ AD (Win 2019) ]   |
|  dlp.ipa.srv.world   +----------+-----------+  fd3s.ad.srv.world   |
|                      |                      |                      |
+----------------------+                      +----------------------+

[1] Install required packages and Setup trust on FreeIPA Server.
[root@dlp ~]#
dnf module -y install idm:DL1/adtrust
[root@dlp ~]#

The log file for this installation can be found in /var/log/ipaserver-install.log
This program will setup components needed to establish trust to AD domains for
the IPA Server.

This includes:
  * Configure Samba
  * Add trust related objects to IPA LDAP server

To accept the default shown in brackets, press the Enter key.

Configuring cross-realm trusts for IPA server requires password for user 'admin'.
This user is a regular system account used for IPA server administration.

# FreeIPA admin password
admin password:

WARNING: The smb.conf already exists. Running ipa-adtrust-install will break your existing samba configuration.

# confirm smb.conf is over written
Do you wish to continue? [no]: yes
Do you want to enable support for trusted domains in Schema Compatibility plugin?
This will allow clients older than SSSD 1.9 and non-Linux clients to work with trusted users.

# enable slapi-nis or not
Enable trusted domains support in slapi-nis? [no]:

Trust is configured but no NetBIOS domain name found, setting it now.
Enter the NetBIOS name for the IPA domain.
Only up to 15 uppercase ASCII letters, digits and dashes are allowed.
Example: EXAMPLE.

# set NetBIOS name for FreeIPA domain
NetBIOS domain name [IPA]: IPA01

WARNING: 9 existing users or groups do not have a SID identifier assigned.
Installer can run a task to have ipa-sidgen Directory Server plugin generate
the SID identifier for all these users. Please note, in case of a high
number of users and groups, the operation might lead to high replication
traffic and performance degradation. Refer to ipa-adtrust-install(1) man page
for details.

# run task or not to set SID for existing users
Do you want to run the ipa-sidgen task? [no]: yes

The following operations may take some minutes to complete.
Please wait until the prompt is returned.

Configuring CIFS
  [1/24]: validate server hostname
  [2/24]: stopping smbd
  [3/24]: creating samba domain object


  [22/24]: starting CIFS services
  [23/24]: adding SIDs to existing users and groups
This step may take considerable amount of time, please wait..
  [24/24]: restarting smbd
Done configuring CIFS.

You must make sure these network ports are open:
        TCP Ports:
          * 135: epmap
          * 138: netbios-dgm
          * 139: netbios-ssn
          * 445: microsoft-ds
          * 1024..1300: epmap listener range
          * 3268: msft-gc
        UDP Ports:
          * 138: netbios-dgm
          * 139: netbios-ssn
          * 389: (C)LDAP
          * 445: microsoft-ds

See the ipa-adtrust-install(1) man page for more details


# if firewalld is running, allow service

[root@dlp ~]#
firewall-cmd --add-service=freeipa-trust --permanent

[root@dlp ~]#
firewall-cmd --reload

[2] Add DNS Setting on FreeIPA Server.
# ipa dnsforwardzone-add [AD domain name] --forwarder=[AD IP address] --forward-policy=only

[root@dlp ~]#
ipa dnsforwardzone-add ad.srv.world --forwarder= --forward-policy=only

Server will check DNS forwarder(s).
This may take some time, please wait ...
  Zone name: ad.srv.world.
  Active zone: TRUE
  Zone forwarders:
  Forward policy: only

# ipa dnszone-mod [IPA domain name] --allow-transfer=[AD IP address]

[root@dlp ~]#
ipa dnszone-mod ipa.srv.world --allow-transfer=

  Zone name: ipa.srv.world.
  Active zone: TRUE
  Authoritative nameserver: dlp.ipa.srv.world.
  Administrator e-mail address: hostmaster.ipa.srv.world.
  SOA serial: 1615363082
  SOA refresh: 3600
  SOA retry: 900
  SOA expire: 1209600
  SOA minimum: 3600
  BIND update policy: grant IPA.SRV.WORLD krb5-self * A; grant IPA.SRV.WORLD krb5-self * AAAA; grant IPA.SRV.WORLD krb5-self * SSHFP;
  Dynamic update: TRUE
  Allow query: any;
  Allow transfer:;
[3] Add FreeIPA Domain to Zones on Windows Active Directory Server.
⇒ dnscmd /ZoneAdd [IPA domain name] /Secondary [IPA IP address]
[4] Verify Name resolution and if no ploblem, Setup trust.
[root@dlp ~]#
dig SRV _ldap._tcp.ipa.srv.world

; <<>> DiG 9.11.26-RedHat-9.11.26-3.el8 <<>> SRV _ldap._tcp.ipa.srv.world
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36308
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 3

; EDNS: version: 0, flags:; udp: 1232
; COOKIE: 84c28432edb77387308f283460488032951d1ba04c33f8bd (good)
;_ldap._tcp.ipa.srv.world.      IN      SRV

_ldap._tcp.ipa.srv.world. 86400 IN      SRV     0 100 389 dlp.ipa.srv.world.
_ldap._tcp.ipa.srv.world. 86400 IN      SRV     0 100 389 node01.ipa.srv.world.

ipa.srv.world.          86400   IN      NS      dlp.ipa.srv.world.
ipa.srv.world.          86400   IN      NS      node01.ipa.srv.world.

[root@dlp ~]#
dig SRV _ldap._tcp.ad.srv.world

; <<>> DiG 9.11.26-RedHat-9.11.26-3.el8 <<>> SRV _ldap._tcp.ad.srv.world
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57916
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 2

; EDNS: version: 0, flags:; udp: 1232
; COOKIE: 4ddb5bd17c57817b0abe2c856048806567a2754344f5fec5 (good)
;_ldap._tcp.ad.srv.world.       IN      SRV

_ldap._tcp.ad.srv.world. 600    IN      SRV     0 100 389 fd3s.ad.srv.world.

fd3s.ad.srv.world.      3600    IN      A

# ipa trust-add --type=ad [AD domain name] --admin Administrator --password

[root@dlp ~]#
ipa trust-add --two-way=true --type=ad ad.srv.world --admin Administrator --password

Active Directory domain administrator's password:
Added Active Directory trust for realm "ad.srv.world"
  Realm name: ad.srv.world
  Domain NetBIOS name: FD3S01
  Domain Security Identifier: S-1-5-21-3321637719-508501573-2242745825
  Trust direction: Two-way trust
  Trust type: Active Directory domain
  Trust status: Established and verified

# verify possbile to get any AD user info

[root@dlp ~]#
id Serverworld@ad.srv.world

uid=1053201103(serverworld@ad.srv.world) gid=1053201103(serverworld@ad.srv.world) groups=1053201103(serverworld@ad.srv.world),1053200513(domain users@ad.srv.world)

# set if you need (creare home directory at initial login)

[root@dlp ~]#
authselect enable-feature with-mkhomedir

[root@dlp ~]#
systemctl enable --now oddjobd
# verify possible to login with any AD user

[root@dlp ~]#


CentOS Stream 8
Kernel 4.18.0-277.el8.x86_64 on an x86_64

Activate the web console with: systemctl enable --now cockpit.socket

dlp login: Serverworld@ad.srv.world
Last login: Wed Mar 09 19:20:33 on ttyS0
[serverworld@ad.srv.world@dlp /]$      # just logined
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