Chapter 4. Configuring Capsule Server with External Services

Procedure

1. On your Red Hat Enterprise Linux host, install the ISC DHCP Service and Berkeley Internet Name Domain (BIND) utilities packages:

   # dnf install dhcp-server bind-utils

2. Generate a security token:

   # tsig-keygen -a hmac-md5 omapi_key

3. Edit the dhcpd configuration file for all subnets and add the key generated by tsig-keygen. The following is an example:

   # cat /etc/dhcp/dhcpd.conf
   default-lease-time 604800;
   max-lease-time 2592000;
   log-facility local7;
   
   subnet 192.168.38.0 netmask 255.255.255.0 {
   	range 192.168.38.10 192.168.38.100;
   	option routers 192.168.38.1;
   	option subnet-mask 255.255.255.0;
   	option domain-search "virtual.lan";
   	option domain-name "virtual.lan";
   	option domain-name-servers 8.8.8.8;
   }
   
   omapi-port 7911;
   key omapi_key {
   	algorithm hmac-md5;
   	secret "My_Secret";
   };
   omapi-key omapi_key;

   Note that the option routers value is the IP address of your Satellite Server or Capsule Server that you want to use with an external DHCP service.

4. On Satellite Server, define each subnet. Do not set DHCP Capsule for the defined Subnet yet.

   To prevent conflicts, set up the lease and reservation ranges separately. For example, if the lease range is 192.168.38.10 to 192.168.38.100, in the Satellite web UI define the reservation range as 192.168.38.101 to 192.168.38.250.

5. Configure the firewall for external access to the DHCP server:

   # firewall-cmd --add-service dhcp \
   && firewall-cmd --runtime-to-permanent

6. On Satellite Server, determine the UID and GID of the foreman user:

   # id -u foreman
   993
   # id -g foreman
   990

7. On the DHCP server, create the foreman user and group with the same IDs as determined in a previous step:

   # groupadd -g 990 foreman
   # useradd -u 993 -g 990 -s /sbin/nologin foreman

8. To ensure that the configuration files are accessible, restore the read and execute flags:

   # chmod o+rx /etc/dhcp/
   # chmod o+r /etc/dhcp/dhcpd.conf
   # chattr +i /etc/dhcp/ /etc/dhcp/dhcpd.conf

9. Enable and start the DHCP service:

   # systemctl enable --now dhcpd

10. Export the DHCP configuration and lease files using NFS:

    # dnf install nfs-utils
    # systemctl enable --now nfs-server

11. Create directories for the DHCP configuration and lease files that you want to export using NFS:

    # mkdir -p /exports/var/lib/dhcpd /exports/etc/dhcp

12. To create mount points for the created directories, add the following line to the /etc/fstab file:

    /var/lib/dhcpd /exports/var/lib/dhcpd none bind,auto 0 0
    /etc/dhcp /exports/etc/dhcp none bind,auto 0 0

13. Mount the file systems in /etc/fstab:

    # mount -a

14. Ensure the following lines are present in /etc/exports:

    /exports 192.168.38.1(rw,async,no_root_squash,fsid=0,no_subtree_check)
    
    /exports/etc/dhcp 192.168.38.1(ro,async,no_root_squash,no_subtree_check,nohide)
    
    /exports/var/lib/dhcpd 192.168.38.1(ro,async,no_root_squash,no_subtree_check,nohide)

    Note that the IP address that you enter is the Satellite or Capsule IP address that you want to use with an external DHCP service.

15. Reload the NFS server:

    # exportfs -rva

16. Configure the firewall for DHCP omapi port 7911:

    # firewall-cmd --add-port=7911/tcp
    # firewall-cmd --runtime-to-permanent

17. Optional: Configure the firewall for external access to NFS. Clients are configured using NFSv3.

    # firewall-cmd --zone public --add-service mountd \
    && firewall-cmd --zone public --add-service rpc-bind \
    && firewall-cmd --zone public --add-service nfs \
    && firewall-cmd --runtime-to-permanent

Procedure

1. Install the nfs-utils package:

   # dnf install nfs-utils

2. Create the DHCP directories for NFS:

   # mkdir -p /mnt/nfs/etc/dhcp /mnt/nfs/var/lib/dhcpd

3. Change the file owner:

   # chown -R foreman-proxy /mnt/nfs

4. Verify communication with the NFS server and the Remote Procedure Call (RPC) communication paths:

   # showmount -e DHCP_Server_FQDN
   # rpcinfo -p DHCP_Server_FQDN

5. Add the following lines to the /etc/fstab file:

   DHCP_Server_FQDN:/exports/etc/dhcp /mnt/nfs/etc/dhcp nfs
   ro,vers=3,auto,nosharecache,context="system_u:object_r:dhcp_etc_t:s0" 0 0
   
   DHCP_Server_FQDN:/exports/var/lib/dhcpd /mnt/nfs/var/lib/dhcpd nfs
   ro,vers=3,auto,nosharecache,context="system_u:object_r:dhcpd_state_t:s0" 0 0

6. Mount the file systems on /etc/fstab:

   # mount -a

7. To verify that the foreman-proxy user can access the files that are shared over the network, display the DHCP configuration and lease files:

   # su foreman-proxy -s /bin/bash
   bash-4.2$ cat /mnt/nfs/etc/dhcp/dhcpd.conf
   bash-4.2$ cat /mnt/nfs/var/lib/dhcpd/dhcpd.leases
   bash-4.2$ exit

8. Enter the satellite-installer command to make the following persistent changes to the /etc/foreman-proxy/settings.d/dhcp.yml file:

   # satellite-installer --foreman-proxy-dhcp=true \
   --foreman-proxy-dhcp-provider=remote_isc \
   --foreman-proxy-plugin-dhcp-remote-isc-dhcp-config /mnt/nfs/etc/dhcp/dhcpd.conf \
   --foreman-proxy-plugin-dhcp-remote-isc-dhcp-leases /mnt/nfs/var/lib/dhcpd/dhcpd.leases \
   --foreman-proxy-plugin-dhcp-remote-isc-key-name=omapi_key \
   --foreman-proxy-plugin-dhcp-remote-isc-key-secret=jNSE5YI3H1A8Oj/tkV4...A2ZOHb6zv315CkNAY7DMYYCj48Umw== \
   --foreman-proxy-plugin-dhcp-remote-isc-omapi-port=7911 \
   --enable-foreman-proxy-plugin-dhcp-remote-isc \
   --foreman-proxy-dhcp-server=DHCP_Server_FQDN

9. Associate the DHCP service with the appropriate subnets and domain.

Creating a Kerberos Principal on the IdM Server

1. Obtain a Kerberos ticket for the account obtained from the IdM administrator:

   # kinit idm_user

2. Create a new Kerberos principal for Capsule Server to use to authenticate on the IdM server.

   # ipa service-add capsule.example.com

Installing and Configuring the IdM Client

1. On the base operating system of either the Satellite or Capsule that is managing the DNS service for your deployment, install the ipa-client package:

   # satellite-maintain packages install ipa-client

2. Configure the IdM client by running the installation script and following the on-screen prompts:

   # ipa-client-install

3. Obtain a Kerberos ticket:

   # kinit admin

4. Remove any preexisting keytab:

   # rm /etc/foreman-proxy/dns.keytab

5. Obtain the keytab for this system:

   # ipa-getkeytab -p capsule/satellite.example.com@EXAMPLE.COM \
   -s idm1.example.com -k /etc/foreman-proxy/dns.keytab

   Note

   When adding a keytab to a standby system with the same host name as the original system in service, add the r option to prevent generating new credentials and rendering the credentials on the original system invalid.

6. For the dns.keytab file, set the group and owner to foreman-proxy:

   # chown foreman-proxy:foreman-proxy /etc/foreman-proxy/dns.keytab

7. Optional: To verify that the keytab file is valid, enter the following command:

   # kinit -kt /etc/foreman-proxy/dns.keytab \
   capsule/satellite.example.com@EXAMPLE.COM

Configuring DNS Zones in the IdM web UI

1. Create and configure the zone that you want to manage:

   1. Navigate to Network Services > DNS > DNS Zones.
   2. Select Add and enter the zone name. For example, example.com.
   3. Click Add and Edit.

   4. Click the Settings tab and in the BIND update policy box, add the following to the semi-colon separated list:

      grant capsule\047satellite.example.com@EXAMPLE.COM wildcard * ANY;

   5. Set Dynamic update to True.
   6. Enable Allow PTR sync.
   7. Click Save to save the changes.

2. Create and configure the reverse zone:

   1. Navigate to Network Services > DNS > DNS Zones.
   2. Click Add.
   3. Select Reverse zone IP network and add the network address in CIDR format to enable reverse lookups.
   4. Click Add and Edit.

   5. Click the Settings tab and in the BIND update policy box, add the following to the semi-colon separated list:

      grant capsule\047satellite.example.com@EXAMPLE.COM wildcard * ANY;

   6. Set Dynamic update to True.
   7. Click Save to save the changes.

Configuring the Satellite or Capsule Server that Manages the DNS Service for the Domain

1. Use the satellite-installer command to configure the Satellite or Capsule that manages the DNS Service for the domain:

   • On Satellite, enter the following command:

     # satellite-installer --scenario satellite \
     --foreman-proxy-dns-managed=false \
     --foreman-proxy-dns-provider=nsupdate_gss \
     --foreman-proxy-dns-server="idm1.example.com" \
     --foreman-proxy-dns-tsig-keytab=/etc/foreman-proxy/dns.keytab \
     --foreman-proxy-dns-tsig-principal="capsule/satellite.example.com@EXAMPLE.COM" \
     --foreman-proxy-dns=true

   • On Capsule, enter the following command:

     # satellite-installer --scenario capsule \
     --foreman-proxy-dns-managed=false \
     --foreman-proxy-dns-provider=nsupdate_gss \
     --foreman-proxy-dns-server="idm1.example.com" \
     --foreman-proxy-dns-tsig-keytab=/etc/foreman-proxy/dns.keytab \
     --foreman-proxy-dns-tsig-principal="capsule/satellite.example.com@EXAMPLE.COM" \
     --foreman-proxy-dns=true

Updating the Configuration in the Satellite web UI

1. In the Satellite web UI, navigate to Infrastructure > Capsules, locate the Capsule Server, and from the list in the Actions column, select Refresh.

2. Configure the domain:

   1. In the Satellite web UI, navigate to Infrastructure > Domains and select the domain name.
   2. In the Domain tab, ensure DNS Capsule is set to the Capsule where the subnet is connected.

3. Configure the subnet:

   1. In the Satellite web UI, navigate to Infrastructure > Subnets and select the subnet name.
   2. In the Subnet tab, set IPAM to None.
   3. In the Domains tab, select the domain that you want to manage using the IdM server.
   4. In the Capsules tab, ensure Reverse DNS Capsule is set to the Capsule where the subnet is connected.
   5. Click Submit to save the changes.

Enabling External Updates to the DNS Zone in the IdM Server

1. On the IdM Server, add the following to the top of the /etc/named.conf file:

   ########################################################################
   
   include "/etc/rndc.key";
   controls  {
   inet _IdM_Server_IP_Address_ port 953 allow { _Satellite_IP_Address_; } keys { "rndc-key"; };
   };
   ########################################################################

2. Reload the named service to make the changes take effect:

   # systemctl reload named

3. In the IdM web UI, navigate to Network Services > DNS > DNS Zones and click the name of the zone. In the Settings tab, apply the following changes:

   1. Add the following in the BIND update policy box:

      grant "rndc-key" zonesub ANY;

   2. Set Dynamic update to True.
   3. Click Update to save the changes.

4. Copy the /etc/rndc.key file from the IdM server to the base operating system of your Satellite Server. Enter the following command:

   # scp /etc/rndc.key root@satellite.example.com:/etc/rndc.key

5. To set the correct ownership, permissions, and SELinux context for the rndc.key file, enter the following command:

   # restorecon -v /etc/rndc.key
   # chown -v root:named /etc/rndc.key
   # chmod -v 640 /etc/rndc.key

6. Assign the foreman-proxy user to the named group manually. Normally, satellite-installer ensures that the foreman-proxy user belongs to the named UNIX group, however, in this scenario Satellite does not manage users and groups, therefore you need to assign the foreman-proxy user to the named group manually.

   # usermod -a -G named foreman-proxy

7. On Satellite Server, enter the following satellite-installer command to configure Satellite to use the external DNS server:

   # satellite-installer --scenario satellite \
   --foreman-proxy-dns=true \
   --foreman-proxy-dns-managed=false \
   --foreman-proxy-dns-provider=nsupdate \
   --foreman-proxy-dns-server="IdM_Server_IP_Address" \
   --foreman-proxy-keyfile=/etc/rndc.key \
   --foreman-proxy-dns-ttl=86400

Testing External Updates to the DNS Zone in the IdM Server

1. Ensure that the key in the /etc/rndc.key file on Satellite Server is the same key file that is used on the IdM server:

   key "rndc-key" {
           algorithm hmac-md5;
           secret "secret-key==";
   };

2. On Satellite Server, create a test DNS entry for a host. For example, host test.example.com with an A record of 192.168.25.20 on the IdM server at 192.168.25.1.

   # echo -e "server 192.168.25.1\n \
   update add test.example.com 3600 IN A 192.168.25.20\n \
   send\n" | nsupdate -k /etc/rndc.key

3. On Satellite Server, test the DNS entry:

   # nslookup test.example.com 192.168.25.1
   Server:		192.168.25.1
   Address:	192.168.25.1#53
   
   Name:	test.example.com
   Address: 192.168.25.20

4. To view the entry in the IdM web UI, navigate to Network Services > DNS > DNS Zones. Click the name of the zone and search for the host by name.

5. If resolved successfully, remove the test DNS entry:

   # echo -e "server 192.168.25.1\n \
   update delete test.example.com 3600 IN A 192.168.25.20\n \
   send\n" | nsupdate -k /etc/rndc.key

6. Confirm that the DNS entry was removed:

   # nslookup test.example.com 192.168.25.1

   The above nslookup command fails and returns the SERVFAIL error message if the record was successfully deleted.

Updating the Configuration in the Satellite web UI

1. In the Satellite web UI, navigate to Infrastructure > Capsules.
2. For each Capsule that you want to update, from the Actions list, select Refresh.

3. Configure the domain:

   1. In the Satellite web UI, navigate to Infrastructure > Domains and click the domain name that you want to configure.
   2. In the Domain tab, set DNS Capsule to the Capsule where the subnet is connected.

4. Configure the subnet:

   1. In the Satellite web UI, navigate to Infrastructure > Subnets and select the subnet name.
   2. In the Subnet tab, set IPAM to DHCP or Internal DB.
   3. In the Domains tab, select the domain that you want to manage using Satellite or Capsule.
   4. In the Capsules tab, set Reverse DNS Capsule to the Capsule where the subnet is connected.
   5. Click Submit to save the changes.