Setup a Linux server as IDM client to authenticate with Active Directory


In our previous guide setting up a cross-forest trust has been elaborated. By following we are continuing with client setup in IDM series.

Let’s walk through all required steps to accomplish a successful client and server communication using IDM cross-forest trust.

The steps we are going to follow in this guide is as follows.

  • Configure Firewall
  • Installing Package
  • Configuring static IP for IDM client
  • Verify DNS
  • Run client setup
  • Verify accounts
  • Login and confirm AD accounts

IDM Client-Server Info

IP AddressHostname

Firewall for IDM Clients

By default, RHEL, CentOS, Oracle Linux are not coming with free IPA clients services for firewall so let’s create one and use it.

Create a firewall service XML under below location

# vim /usr/lib/firewalld/services/freeipa-clients.xml
[root@vcs1 ~]# cat /usr/lib/firewalld/services/freeipa-clients.xml
<?xml version="1.0" encoding="utf-8"?>
  <short>FreeIPA Client</short>
  <description>FreeIPA Clients Required Ports.</description>
  <port protocol="tcp" port="80"/>
  <port protocol="tcp" port="88"/>
  <port protocol="tcp" port="389"/>
  <port protocol="udp" port="88"/>
  <port protocol="tcp" port="464"/>
  <port protocol="udp" port="464"/>
  <port protocol="udp" port="123"/>

Once service XML created reload the firewall-cmd, By following permanently add the freeIPA client’s service and reload the firewall to take effect.

# firewall-cmd --reload
# firewall-cmd --add-service=freeipa-clients --permanent
# firewall-cmd --reload
# firewall-cmd --list-all
[root@client1 ~]# firewall-cmd --list-all
 public (active)
   target: default
   icmp-block-inversion: no
   interfaces: ens33
   services: ssh dhcpv6-client freeipa-clients
   masquerade: no
   rich rules: 
 [root@client1 ~]#

Installing IDM Client Package

Now it’s time to install the client package, by running the yum install will pull down all required dependencies and install the client.

# yum install ipa-client -y
   ipa-client.x86_64 0:4.6.4-10.el7                                                                                                                                                   
 Dependency Installed:
   autofs.x86_64 1:5.0.7-99.el7                                      autogen-libopts.x86_64 0:5.18-5.el7                       avahi-libs.x86_64 0:0.6.31-19.el7                      
   c-ares.x86_64 0:1.10.0-3.el7                                      certmonger.x86_64 0:0.78.4-10.el7                         cups-libs.x86_64 1:1.6.3-35.el7                        
   cyrus-sasl-gssapi.x86_64 0:2.1.26-23.el7                          gssproxy.x86_64 0:0.7.0-21.el7                            hesiod.x86_64 0:3.2.1-3.el7                            
   http-parser.x86_64 0:2.7.1-5.el7_4                                ipa-client-common.noarch 0:4.6.4-10.el7                   ipa-common.noarch 0:4.6.4-10.el7                       
   keyutils.x86_64 0:1.5.8-3.el7                                     krb5-workstation.x86_64 0:1.15.1-34.el7                   libbasicobjects.x86_64 0:0.1.1-32.el7                  
   libcollection.x86_64 0:0.7.0-32.el7                               libdhash.x86_64 0:0.5.0-32.el7                            libevent.x86_64 0:2.0.21-4.el7                         
   libini_config.x86_64 0:1.3.1-32.el7                               libipa_hbac.x86_64 0:1.16.2-13.el7                        libkadm5.x86_64 0:1.15.1-34.el7                        
   libldb.x86_64 0:1.3.4-1.el7                                       libnfsidmap.x86_64 0:0.25-19.el7                          libpath_utils.x86_64 0:0.2.1-32.el7                    
   libref_array.x86_64 0:0.1.5-32.el7                                libsmbclient.x86_64 0:4.8.3-4.el7                         libsss_autofs.x86_64 0:1.16.2-13.el7                   
   libsss_certmap.x86_64 0:1.16.2-13.el7                             libsss_idmap.x86_64 0:1.16.2-13.el7                       libsss_nss_idmap.x86_64 0:1.16.2-13.el7                
   libsss_sudo.x86_64 0:1.16.2-13.el7                                libtalloc.x86_64 0:2.1.13-1.el7                           libtdb.x86_64 0:1.3.15-1.el7                           
   libtevent.x86_64 0:0.9.36-1.el7                                   libtirpc.x86_64 0:0.2.4-0.15.el7                          libverto-tevent.x86_64 0:0.2.5-4.el7                   
   libwbclient.x86_64 0:4.8.3-4.el7                                  nfs-utils.x86_64 1:1.3.0-0.61.el7                         ntp.x86_64 0:4.2.6p5-28.el7                            
   ntpdate.x86_64 0:4.2.6p5-28.el7                                   oddjob.x86_64 0:0.31.5-4.el7                              oddjob-mkhomedir.x86_64 0:0.31.5-4.el7                 
   psmisc.x86_64 0:22.20-15.el7                                      python-cffi.x86_64 0:1.6.0-5.el7                          python-chardet.noarch 0:2.2.1-1.el7_1                  
   python-dns.noarch 0:1.12.0-4.20150617git465785f.el7               python-enum34.noarch 0:1.0.4-1.el7                        python-gssapi.x86_64 0:1.2.0-3.el7                     
   python-idna.noarch 0:2.4-1.el7                                    python-jwcrypto.noarch 0:0.4.2-1.el7                      python-ldap.x86_64 0:2.4.15-2.el7                      
   python-libipa_hbac.x86_64 0:1.16.2-13.el7                         python-netaddr.noarch 0:0.7.5-9.el7                       python-netifaces.x86_64 0:0.10.4-3.el7                 
   python-nss.x86_64 0:0.16.0-3.el7                                  python-ply.noarch 0:3.4-11.el7                            python-pycparser.noarch 0:2.14-1.el7                   
   python-qrcode-core.noarch 0:5.0.1-1.el7                           python-requests.noarch 0:2.6.0-1.el7_1                    python-sss-murmur.x86_64 0:1.16.2-13.el7               
   python-sssdconfig.noarch 0:1.16.2-13.el7                          python-urllib3.noarch 0:1.10.2-5.el7                      python-yubico.noarch 0:1.2.3-1.el7                     
   python2-cryptography.x86_64 0:1.7.2-2.el7                         python2-ipaclient.noarch 0:4.6.4-10.el7                   python2-ipalib.noarch 0:4.6.4-10.el7                   
   python2-pyasn1.noarch 0:0.1.9-7.el7                               python2-pyasn1-modules.noarch 0:0.1.9-7.el7               pyusb.noarch 0:1.0.0-0.11.b1.el7                       
   quota.x86_64 1:4.01-17.el7                                        quota-nls.noarch 1:4.01-17.el7                            rpcbind.x86_64 0:0.2.0-47.el7                          
   samba-client-libs.x86_64 0:4.8.3-4.el7                            samba-common.noarch 0:4.8.3-4.el7                         samba-common-libs.x86_64 0:4.8.3-4.el7                 
   sssd.x86_64 0:1.16.2-13.el7                                       sssd-ad.x86_64 0:1.16.2-13.el7                            sssd-client.x86_64 0:1.16.2-13.el7                     
   sssd-common.x86_64 0:1.16.2-13.el7                                sssd-common-pac.x86_64 0:1.16.2-13.el7                    sssd-ipa.x86_64 0:1.16.2-13.el7                        
   sssd-krb5.x86_64 0:1.16.2-13.el7                                  sssd-krb5-common.x86_64 0:1.16.2-13.el7                   sssd-ldap.x86_64 0:1.16.2-13.el7                       
   sssd-proxy.x86_64 0:1.16.2-13.el7                                 tcp_wrappers.x86_64 0:7.6-77.el7                          xmlrpc-c.x86_64 0:1.32.5-1905.svn2451.el7              
   xmlrpc-c-client.x86_64 0:1.32.5-1905.svn2451.el7                 
 [root@client1 ~]#

There will be a lot of dependencies for IPA-client, Make sure to use a yum repository.

Configure static IP address

In our setup we are using static IP, so we have configured as follows. Use the IDM server’s IP as DNS IP of all client servers.

[root@client1 ~]# cat /etc/sysconfig/network-scripts/ifcfg-ens33 

Verify DNS by cat the resolv.conf

[root@client1 ~]# cat /etc/resolv.conf 
 Generated by NetworkManager
 search linuxsysadmins.local
 [root@client1 ~]#

Or verify using dig command

# dig linuxsysadmins.local @
# dig -x

Run Client setup

Start to set up the client by running “ipa-client-install” command with options and argument.

# ipa-client-install --enable-dns-updates --force-ntpd --mkhomedir
# ipa-client-install --domain linuxsysadmins.local --server idmns.linuxsysadmins.local --realm LINUXSYSADMINS.LOCAL
  • ipa-client-install – Command to run the client setup.
  • –enable-dns-updates – To get the DNS information.
  • –force-ntpd – Force to get the time from IDM server.
  • –mkhomedir – Create the user’s home directory on their first login.
IPA Client configure
IPA Client configure
[root@client1 ~]# ipa-client-install --enable-dns-updates --force-ntpd --mkhomedir
 Discovery was successful!
 Client hostname: client1.linuxsysadmins.local
 DNS Domain: linuxsysadmins.local
 IPA Server: idmns.linuxsysadmins.local
 BaseDN: dc=linuxsysadmins,dc=local
 Continue to configure the system with these values? [no]: yes
 Synchronizing time with KDC…
 Attempting to sync time using ntpd.  Will timeout after 15 seconds
 User authorized to enroll computers: admin
 Password for admin@LINUXSYSADMINS.LOCAL: 
 Successfully retrieved CA cert
     Subject:     CN=Certificate Authority,O=LINUXSYSADMINS.LOCAL
     Issuer:      CN=Certificate Authority,O=LINUXSYSADMINS.LOCAL
     Valid From:  2019-06-19 19:53:50
     Valid Until: 2039-06-19 19:53:50
 Created /etc/ipa/default.conf
 New SSSD config will be created
 Configured sudoers in /etc/nsswitch.conf
 Configured /etc/sssd/sssd.conf
 Configured /etc/krb5.conf for IPA realm LINUXSYSADMINS.LOCAL
 trying https://idmns.linuxsysadmins.local/ipa/json
 trying https://idmns.linuxsysadmins.local/ipa/session/json
 Systemwide CA database updated.
 Adding SSH public key from /etc/ssh/
 Adding SSH public key from /etc/ssh/
 Adding SSH public key from /etc/ssh/
 SSSD enabled
 Configured /etc/openldap/ldap.conf
 NTP enabled
 Configured /etc/ssh/ssh_config
 Configured /etc/ssh/sshd_config
 Configuring linuxsysadmins.local as NIS domain.
 Client configuration complete.
 The ipa-client-install command was successful
[root@client1 ~]#

Linux client Integrated successfully with IDM.

Check for AD accounts in IDM server

For a quick check just run “getent” to know whether it’s working as expected.

# getent passwd babin@winlinuxsysadmins.local
# getent passwd lonston@winlinuxsysadmins.local
# getent passwd raja@winlinuxsysadmins.local

We got the output for all AD accounts query.

[root@client1 ~]# getent passwd babin@winlinuxsysadmins.local
 babin@winlinuxsysadmins.local::916001104:916001104:Bobin L.:/home/winlinuxsysadmins.local/babin:
[root@client1 ~]# getent passwd lonston@winlinuxsysadmins.local
lonston@winlinuxsysadmins.local::916001105:916001105:Lonston L.:/home/winlinuxsysadmins.local/lonston:
[root@client1 ~]# getent passwd raja@winlinuxsysadmins.local

Login using AD account

Let’s try to login from my laptop to confirm whether AD account working on IDM client.

$ ssh raja@winlinuxsysadmins.local@

We are good at everything.

xxxxxxxxxx@xxxxxxxxxs-MacBook-Pro:~$ ssh raja@winlinuxsysadmins.local@
 Creating home directory for raja@winlinuxsysadmins.local.
 -sh-4.2$ pwd
 -sh-4.2$ ls -lthr
 total 0
 -sh-4.2$ ls -lthra
 total 12K
 drwx--x--x. 3 root                         root                          18 Jun 25 21:57 ..
 -rw-------. 1 raja@winlinuxsysadmins.local raja@winlinuxsysadmins.local  18 Jun 25 21:57 .bash_logout
 -rw-------. 1 raja@winlinuxsysadmins.local raja@winlinuxsysadmins.local 193 Jun 25 21:57 .bash_profile
 -rw-------. 1 raja@winlinuxsysadmins.local raja@winlinuxsysadmins.local 231 Jun 25 21:57 .bashrc
 drwx------. 2 raja@winlinuxsysadmins.local raja@winlinuxsysadmins.local  62 Jun 25 21:57 .
 -sh-4.2$ id
 uid=916001110(raja@winlinuxsysadmins.local) gid=916001110(raja@winlinuxsysadmins.local) groups=916001110(raja@winlinuxsysadmins.local),916000513(domain users@winlinuxsysadmins.local),916001108(winteladmins@winlinuxsysadmins.local) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

Verifying Conditional DNS forward from IDM Client

In our IDM/AD Server setup we have a DNS conditional forwarder, Let’s test one of “A record” created on AD/DNS server from IDM client.

For testing purpose created with two “A record” entry on AD as follows.

Test DNS entry for conditional forward
Test DNS entry for conditional forward

Run dig command to verify one of “A record” in AD servers.

Setup a Linux server as IDM client to authenticate with Active Directory 1
Dig for an “A record” in AD/DNS server
  1. Query/Question about client2.winlinuxsysadmins.local
  2. Answer received from IDM by resolving conditional forwarding on AD
  3. The IP address of the “A record” on AD/DNS (addns.winlinuxsysadmins.local)
  4. Getting Answer from IDM server (|idmns.linuxsysadmins.local)

Or a simple check we can use the “host” command.

[root@client1 ~]#
 [root@client1 ~]# host winclient.winlinuxsysadmins.local
 winclient.winlinuxsysadmins.local has address
 [root@client1 ~]# 
 [root@client1 ~]# host client2.winlinuxsysadmins.local
 client2.winlinuxsysadmins.local has address
 [root@client1 ~]# 
 [root@client1 ~]# host client1.linuxsysadmins.local
 client1.linuxsysadmins.local has address
 [root@client1 ~]#

That’s it we have completed with a successful IDM & AD cross-forest trust.


Most of the critical production environment are looking for this solution, It’s been for a long time I’m working on this and finally documented each step for self-reference in the future. Hope this guide will help you in the current or future working environment. In case any improvement required in this article your feedback is most welcome in below comment section, Subscribe to our newsletter and stay with us to receive more articles based on Identity Management (IDM).

2 thoughts on “Setup a Linux server as IDM client to authenticate with Active Directory”

  1. I was able to authenticate AD users on Linux. I was also able to set the sudo rules for AD group. Any modification in AD members takes hours to replicate on the Linux servers. Is there any frequency settings that might need to be set?


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