CentOS – Directory Services

Directory Services provide secure central point for management, authentication and authorization of users and computers. They also offer other benefits and capabilities, eg. SSO or other features depending on the specific solution.

The server has secure access via ssh and updates automatically. Now is the time for directory services. They reduce the administrative overhead and managing actions. The most popular is Active Directory – it’s a whizz kid of Microsoft (probably one of the few :). But it’s expensive, and – probably – in many cases you won’t have to use most of AD functions and bear the costs connected with them. There are multiple free solutions: OpenLDAP, Apache Directory and FreeIPA (IdM). This post will be about the latter.

A few words about IPA

FreeIPA (or IdM in RHEL documentation) provides directory services in a Linux based domain with the support for integration with Active Directory. IPA server includes Kerberos KDC, LDAP directory server, Certificate authority, Domain Name System  and Network Time Protocol and runs on the ports:

http/https: 80/tcp, 443/tcp
ldap/ldaps: 389/tcp, 636/tcp
Kerberos: 88/tcp, 464/tcp, 88/tcp, 464/tcp
DNS: 53/tcp, 53/udp
NTP: 123/udp

Documentation recommends at least 3 GB of RAM and 1 GB swap space (simple entry has approximately 5 – 10 KiB) for 10,000 users and 100 groups.

The integrated directory services with implemented Kerberos are very sensitive to wrong configurations of DNS. My starting assumptions are:
– fully qualified server domain name (only lower-case, numbers and hyphen): server.local.test
– not recommended (which means: never do it) is using of a domain which is not delegated to you, even on LAN.
– good practice and recommended solution for global corporate DNS policy is setting as IdM DNS forwarder own DNS server, which delegates to the neutral external DNS server, eg. OpenNIC.

By the way, for proper operation Kerberos requires time synchronization between IdM servers and clients. Red Hat strongly recommends to use more than one domain controller for load balancing and redundancy. Let’s start with the first domain controller.

I. Preparation

1. edit the hosts file and add server IP address and fully qualified domain name

vi /etc/hosts   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6 server.local.test

2. edit the hostname file and set fully qualified domain name

vi /etc/hostname

3. check the DNS configuration

cat /etc/resolv.conf
search local.test

4. check the network config – it should look something like that

vi /etc/sysconfig/network-scripts/ifcfg-enp0s0

5. install the bind utils

yum install bind-utils

6. to test the DNS record of server name – the response should be IP address

dig +short server.local.test A

7. and check the reverse dns – correct response

dig +short -x

8. add the firewalld rules:

firewall-cmd --add-service={dns,ntp,http,https,ldap,ldaps,kerberos,kpasswd}
firewall-cmd --add-service={dns,ntp,http,https,ldap,ldaps,kerberos,kpasswd} --permanent

II. Installation

1. update repositories and system

yum update && yum upgrade

2. install the package

yum install ipa-server-dns

3. run the installation script

ipa-server-install --mkhomedir --setup-dns --auto-forwarders --auto-reverse
The log file for this installation can be found in /var/log/ipaserver-install.log
This program will set up the IPA Server.

This includes:
  * Configure a stand-alone CA (dogtag) for certificate management
  * Configure the Network Time Daemon (ntpd)
  * Create and configure an instance of Directory Server
  * Create and configure a Kerberos Key Distribution Center (KDC)
  * Configure Apache (httpd)

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

WARNING: conflicting time&date synchronization service 'chronyd' will be disabled
in favor of ntpd

Do you want to configure integrated DNS (BIND)? [no]: yes

Existing BIND configuration detected, overwrite? [no]: yes
Enter the fully qualified domain name of the computer
on which you're setting up server software. Using the form
Example: master.example.com.

Server host name [ipaserver.example.com]: server.local.test

Warning: skipping DNS resolution of host ipaserver.example.com
The domain name has been determined based on the host name.

Please confirm the domain name [example.com]: local.test

The kerberos protocol requires a Realm name to be defined.
This is typically the domain name converted to uppercase.

Please provide a realm name [EXAMPLE.COM]: LOCAL.TEST
Certain directory server operations require an administrative user.
This user is referred to as the Directory Manager and has full access
to the Directory for system management tasks and will be added to the
instance of directory server created for IPA.
The password must be at least 8 characters long.

Directory Manager password: ************
Password (confirm): ************

The IPA server requires an administrative user, named 'admin'.
This user is a regular system account used for IPA server administration.

IPA admin password: ************
Password (confirm): ************

Do you want to configure DNS forwarders? [yes]: yes
Enter the IP address of DNS forwarder to use, or press Enter to finish.
Enter IP address for a DNS forwarder:
DNS forwarder added
Enter IP address for a DNS forwarder:
Do you want to configure the reverse zone? [yes]: yes
Please specify the reverse zone name [10.10.10.in-addr.arpa.]: 10.10.10.in-addr.arpa.
Using reverse zone 10.10.10.in-addr.arpa.

The IPA Master Server will be configured with:
Hostname:      server.local.test
IP address:
Domain name:   local.test
Realm name:    LOCAL.TEST

BIND DNS server will be configured to serve IPA domain with:
Reverse zone:  10.10.10.in-addr.arpa.

Continue to configure the system with these values? [no]: yes

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

Configuring NTP daemon (ntpd)
  [1/4]: stopping ntpd
  [2/4]: writing configuration
  [3/4]: configuring ntpd to start on boot
  [4/4]: starting ntpd
Done configuring NTP daemon (ntpd).
Configuring directory server (dirsrv): Estimated time 1 minute
  [1/38]: creating directory server user
  [2/38]: creating directory server instance
  [3/38]: adding default schema
  [4/38]: enabling memberof plugin
  [5/38]: enabling winsync plugin
  [6/38]: configuring replication version plugin
  [7/38]: enabling IPA enrollment plugin
  [8/38]: enabling ldapi
  [9/38]: configuring uniqueness plugin
  [10/38]: configuring uuid plugin
  [11/38]: configuring modrdn plugin
  [12/38]: configuring DNS plugin
  [13/38]: enabling entryUSN plugin
  [14/38]: configuring lockout plugin
  [15/38]: creating indices
  [16/38]: enabling referential integrity plugin
  [17/38]: configuring certmap.conf
  [18/38]: configure autobind for root
  [19/38]: configure new location for managed entries
  [20/38]: configure dirsrv ccache
  [21/38]: enable SASL mapping fallback
  [22/38]: restarting directory server
  [23/38]: adding default layout
  [24/38]: adding delegation layout
  [25/38]: creating container for managed entries
  [26/38]: configuring user private groups
  [27/38]: configuring netgroups from hostgroups
  [28/38]: creating default Sudo bind user
  [29/38]: creating default Auto Member layout
  [30/38]: adding range check plugin
  [31/38]: creating default HBAC rule allow_all
  [32/38]: initializing group membership
  [33/38]: adding master entry
  [34/38]: configuring Posix uid/gid generation
  [35/38]: adding replication acis
  [36/38]: enabling compatibility plugin
  [37/38]: tuning directory server
  [38/38]: configuring directory to start on boot
Done configuring directory server (dirsrv).
Configuring certificate server (pki-tomcatd): Estimated time 3 minutes 30 seconds
  [1/22]: creating certificate server user
  [2/22]: configuring certificate server instance
  [3/22]: stopping certificate server instance to update CS.cfg
  [4/22]: disabling nonces
  [5/22]: set up CRL publishing
  [6/22]: starting certificate server instance
  [7/22]: creating RA agent certificate database
  [8/22]: importing CA chain to RA certificate database
  [9/22]: fixing RA database permissions
  [10/22]: setting up signing cert profile
  [11/22]: set certificate subject base
  [12/22]: enabling Subject Key Identifier
  [13/22]: enabling CRL and OCSP extensions for certificates
  [14/22]: setting audit signing renewal to 2 years
  [15/22]: configuring certificate server to start on boot
  [16/22]: restarting certificate server
  [17/22]: requesting RA certificate from CA
  [18/22]: issuing RA agent certificate
  [19/22]: adding RA agent as a trusted user
  [20/22]: configure certificate renewals
  [21/22]: configure Server-Cert certificate renewal
  [22/22]: Configure HTTP to proxy connections
Done configuring certificate server (pki-tomcatd).
Configuring Kerberos KDC (krb5kdc): Estimated time 30 seconds
  [1/10]: adding sasl mappings to the directory
  [2/10]: adding kerberos container to the directory
  [3/10]: configuring KDC
  [4/10]: initialize kerberos container
  [5/10]: adding default ACIs
  [6/10]: creating a keytab for the directory
  [7/10]: creating a keytab for the machine
  [8/10]: adding the password extension to the directory
  [9/10]: starting the KDC
  [10/10]: configuring KDC to start on boot
Done configuring Kerberos KDC (krb5kdc).
Configuring kadmin
  [1/2]: starting kadmin
  [2/2]: configuring kadmin to start on boot
Done configuring kadmin.
Configuring ipa_memcached
  [1/2]: starting ipa_memcached
  [2/2]: configuring ipa_memcached to start on boot
Done configuring ipa_memcached.
Configuring ipa-otpd
  [1/2]: starting ipa-otpd
  [2/2]: configuring ipa-otpd to start on boot
Done configuring ipa-otpd.
Configuring the web interface (httpd): Estimated time 1 minute
  [1/14]: setting mod_nss port to 443
  [2/14]: setting mod_nss password file
  [3/14]: enabling mod_nss renegotiate
  [4/14]: adding URL rewriting rules
  [5/14]: configuring httpd
  [6/14]: setting up ssl
  [7/14]: setting up browser autoconfig
  [8/14]: publish CA cert
  [9/14]: creating a keytab for httpd
  [10/14]: clean up any existing httpd ccache
  [11/14]: configuring SELinux for httpd
  [12/14]: configure httpd ccache
  [13/14]: restarting httpd
  [14/14]: configuring httpd to start on boot
Done configuring the web interface (httpd).
Applying LDAP updates
Restarting the directory server
Restarting the KDC
Restarting the certificate server
Configuring DNS (named)
  [1/11]: adding DNS container
  [2/11]: setting up our zone
  [3/11]: setting up reverse zone
  [4/11]: setting up our own record
  [5/11]: setting up records for other masters
  [6/11]: setting up CA record
  [7/11]: setting up kerberos principal
  [8/11]: setting up named.conf
  [9/11]: restarting named
  [10/11]: configuring named to start on boot
  [11/11]: changing resolv.conf to point to ourselves
Done configuring DNS (named).

Global DNS configuration in LDAP server is empty
You can use 'dnsconfig-mod' command to set global DNS options that
would override settings in local named.conf files

Restarting the web server
Setup complete

Next steps:
        1. You must make sure these network ports are open:
                TCP Ports:
                  * 80, 443: HTTP/HTTPS
                  * 389, 636: LDAP/LDAPS
                  * 88, 464: kerberos
                  * 53: bind
                UDP Ports:
                  * 88, 464: kerberos
                  * 53: bind
                  * 123: ntp

        2. You can now obtain a kerberos ticket using the command: 'kinit admin'
           This ticket will allow you to use the IPA tools (e.g., ipa user-add)
           and the web user interface.

Be sure to back up the CA certificate stored in /root/cacert.p12
This file is required to create replicas. The password for this
file is the Directory Manager password

4. log in to IPA server as default admin account

kinit admin

5. log in to web interface of our Directory Server


RHEL Identity Managment
FreeIPA Documentation
DNS reverse zones
DNS forward zones

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