Chapter 7. Configuring the Discovery Service

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Red Hat Satellite can detect hosts on a network that are not in your Satellite inventory. These hosts boot the discovery image that performs hardware detection and relays this information back to Satellite Server. This method creates a list of ready-to-provision hosts in Satellite Server without needing to enter the MAC address of each host.

When you boot a blank bare-metal host, the boot menu has two options: local and discovery. If you select discovery to boot the Discovery image, after a few minutes, the Discovery image completes booting and a status screen is displayed.

The Discovery service is enabled by default on Satellite Server. However, the default setting of the global templates is to boot from the local hard drive. To change the default setting, in the Satellite web UI, navigate to Administer > Settings, and click the Provisioning tab. Locate the Default PXE global template entry row, and in the Value column, enter discovery.

PXE mode

To use Satellite Server to provide the Discovery image, install the following RPM packages:

  • tfm-rubygem-foreman_discovery
  • foreman-discovery-image
  • tfm-rubygem-smart_proxy_discovery

The tfm-rubygem-foreman_discovery package contains the Satellite plug-in to handle discovered nodes, connections, and necessary database structures, and API.

The tfm-rubygem-smart_proxy_discovery package configures Capsule Server, such as the integrated Capsule of Satellite Server, to act as a proxy for the Discovery service.

When the installation completes, you can view the new menu option by navigating to Hosts > Discovered Hosts.

7.1. Installing the Discovery Service

Complete the following procedure to enable the Discovery service on Capsule Server.


  1. Enter the following commands on Capsule Server:

    # satellite-maintain packages install foreman-discovery-image tfm-rubygem-smart_proxy_discovery
  2. Restart the satellite-maintain services:

    # satellite-maintain service restart
  3. In the Satellite web UI, navigate to Infrastructure > Capsule.
  4. Click Capsule Server and select Refresh from the Actions list. Locate Discovery in the list of features to confirm the Discovery service is now running.


All subnets with discoverable hosts require an appropriate Capsule Server selected to provide the Discovery service.

To check this, navigate to Infrastructure > Capsules and verify if Capsule Server that you want to use lists the Discovery feature. If not, click Refresh features.

In the Satellite web UI, navigate to Infrastructure > Subnets, select a subnet, click the Capsules tab, and select the Discovery Proxy that you want to use. Perform this for each subnet that you want to use.

7.2. The Provisioning Template PXELinux Discovery Snippet

For BIOS provisioning, the PXELinux global default template in the Hosts > Provisioning Templates window contains the snippet pxelinux_discovery. The snippet has the following lines:

LABEL discovery
  MENU LABEL Foreman Discovery Image
  KERNEL boot/fdi-image/vmlinuz0
  APPEND initrd=boot/fdi-image/initrd0.img rootflags=loop root=live:/fdi.iso rootfstype=auto ro acpi=force rd.luks=0 rd.lvm=0 rd.bootif=0 rd.neednet=0 nomodeset proxy.url=<%= foreman_server_url %> proxy.type=foreman

The KERNEL and APPEND options boot the Discovery image and ramdisk. The APPEND option contains a proxy.url parameter, with the foreman_server_url macro as its argument. This macro resolves to the full URL of Satellite Server.

For UEFI provisioning, the PXEgrub2 global default template in the Hosts > Provisioning Templates window contains the snippet pxegrub2_discovery:

menuentry 'Foreman Discovery Image' --id discovery {
  linuxefi boot/fdi-image/vmlinuz0 rootflags=loop root=live:/fdi.iso rootfstype=auto ro acpi=force rd.luks=0 rd.lvm=0 rd.bootif=0 rd.neednet=0 nomodeset proxy.url=<%= foreman_server_url %> proxy.type=foreman BOOTIF=01-$mac
  initrdefi boot/fdi-image/initrd0.img

To use Capsule to proxy the discovery steps, edit /var/lib/tftpboot/pxelinux.cfg/default or /var/lib/tftpboot/grub2/grub.cfg and change the URL to Capsule Server FQDN you want to use.

The global template is available on Satellite Server and all Capsules that have the TFTP feature enabled.

7.3. Automatic Contexts for Discovered Hosts

Satellite Server assigns an organization and location to discovered hosts according to the following sequence of rules:

  1. If a discovered host uses a subnet defined in Satellite, the host uses the first organization and location associated with the subnet.
  2. If the discovery_organization or discovery_location fact values are set, the discovered host uses these fact values as an organization and location. To set these fact values, navigate to Administer > Settings > Discovered, and add these facts to the Default organization and Default location fields. Ensure that the discovered host’s subnet also belongs to the organization and location set by the fact, otherwise Satellite refuses to set it for security reasons.
  3. If none of the previous conditions exists, Satellite assigns the first Organization and Location ordered by name.

You can change the organization or location using the bulk actions menu of the Discovered hosts page. Select the discovered hosts to modify and select Assign Organization or Assign Location from the Select Action menu.

Note that the foreman_organization and foreman_location facts are no longer valid values for assigning context for discovered hosts. You still can use these facts to configure the host for Puppet runs. To do this, navigate to Administer > Settings > Puppet section and add the foreman_organization and foreman_location facts to the Default organization and Default location fields.

7.4. Discovery Templates and Snippets Settings

To use the Discovery service, you must configure provisioning settings to set Discovery as the default service and set the templates that you want to use.

Setting Discovery Service as Default

For both BIOS and UEFI, to set the Discovery service as the default service that boots for hosts that are not present in your current Satellite inventory, complete the following steps:

  1. In the Satellite web UI, navigate to Administer > Settings and click the Provisioning tab.
  2. For the Default PXE global template entry, in the Value column, enter discovery.

To use a template, in the Satellite web UI, navigate to Administer > Settings and click the Provisioning tab and set the templates that you want to use.

Customizing Templates and Snippets

Templates and snippets are locked to prevent changes. If you want to edit a template or snippet, clone it, save it with a unique name, and then edit the clone.

When you change the template or a snippet it includes, the changes must be propagated to Satellite Server’s default PXE template.

In the Satellite web UI, navigate to Hosts > Provisioning Templates and click Build PXE Default.

This refreshes the default PXE template on Satellite Server.

Additional Settings

The proxy.url argument
During the Satellite installation process, if you use the default option --enable-foreman-plugin-discovery, you can edit the proxy.url argument in the template to set the URL of Capsule Server that provides the discovery service. You can change the proxy.url argument to the IP address or FQDN of another provisioning Capsule that you want to use, but ensure that you append the port number, for example, 9090. If you use an alternative port number with the --foreman-proxy-ssl-port option during Satellite installation, you must add that port number. You can also edit the proxy.url argument to use a Satellite IP address or FQDN so that the discovered hosts communicate directly with Satellite Server.
The proxy.type argument

If you use a Capsule Server FQDN for the proxy.url argument, ensure that you set the proxy.type argument to proxy. If you use a Satellite FQDN, update the proxy.type argument to foreman.

proxy.url= proxy.type=proxy

Rendering the Capsule's Host Name

Satellite 6 deploys the same template to all TFTP Capsules and there is no variable or macro available to render the Capsule’s host name. The hard-coded proxy.url does not not work with two or more TFTP Capsules. As a workaround, every time you click Build PXE Defaults, edit the configuration file in the TFTP directory using SSH, or use a common DNS alias for appropriate subnets.

Tagged VLAN Provisioning

If you want to use tagged VLAN provisioning, and you want the discovery service to send a discovery request, add the following information to the KERNEL option in the discovery template:


7.5. Creating Hosts from Discovered Hosts

Provisioning discovered hosts follows a provisioning process that is similar to PXE provisioning. The main difference is that instead of manually entering the host’s MAC address, you can select the host to provision from the list of discovered hosts.

To use the CLI instead of the web UI, see the CLI procedure.



  1. In the Satellite web UI, navigate to Hosts > Discovered host. Select the host you want to use and click Provision to the right of the list.
  2. Select from one of the two following options:

    • To provision a host from a host group, select a host group, organization, and location, and then click Create Host.
    • To provision a host with further customization, click Customize Host and enter the additional details you want to specify for the new host.
  3. Verify that the fields are populated with values. Note in particular:

    • The Name from the Host tab becomes the DNS name.
    • Satellite Server automatically assigns an IP address for the new host.
    • Satellite Server automatically populates the MAC address from the Discovery results.
  4. Ensure that Satellite Server automatically selects the Managed, Primary, and Provision options for the first interface on the host. If not, select them.
  5. Click the Operating System tab, and verify that all fields contain values. Confirm each aspect of the operating system.
  6. Click Resolve in Provisioning template to check the new host can identify the right provisioning templates to use. The host must resolve to the following provisioning templates:

  7. Click Submit to save the host details.

When the host provisioning is complete, the discovered host becomes a content host. To view the host, navigate to Hosts > Content Hosts.

CLI procedure

  1. Identify the discovered host to use for provisioning:

    # hammer discovery list
  2. Select a host and provision it using a host group. Set a new host name with the --new-name option:

    # hammer discovery provision --name "host_name" \
    --new-name "new_host_name" --organization "My_Organization" \
    --location "My_Location" --hostgroup "My_Host_Group" --build true \
    --enabled true --managed true

    This removes the host from the discovered host listing and creates a host entry with the provisioning settings. The Discovery image automatically resets the host so that it can boot to PXE. The host detects the DHCP service on Satellite Server’s integrated Capsule and starts installing the operating system. The rest of the process is identical to normal PXE workflow described in Section 6.3, “Creating Hosts with Unattended Provisioning”.

7.6. Creating Discovery Rules

As a method of automating the provisioning process for discovered hosts, Satellite provides a feature to create discovery rules. These rules define how discovered hosts automatically provision themselves, based on the assigned host group. For example, you can automatically provision hosts with a high CPU count as hypervisors. Likewise, you can provision hosts with large hard disks as storage servers.

To use the CLI instead of the web UI, see the CLI procedure.

NIC Considerations

Auto provisioning does not currently allow configuring NICs; all systems are being provisioned with the NIC configuration that was detected during discovery. However, you can set the NIC in the kickstart scriplet, using a script, or using configuration management at a later stage.


  1. In the Satellite web UI, navigate to Configure > Discovery rules, and select Create Rule.
  2. In the Name field, enter a name for the rule.
  3. In the Search field, enter the rules to determine whether to provision a host. This field provides suggestions for values you enter and allows operators for multiple rules. For example: cpu_count > 8.
  4. From the Host Group list, select the host group to use as a template for this host.
  5. In the Hostname field, enter the pattern to determine host names for multiple hosts. This uses the same ERB syntax that provisioning templates use. The host name can use the @host attribute for host-specific values and the rand macro for a random number or the sequence_hostgroup_param_next macro for incrementing the value. For more information about provisioning templates, see Section 2.11, “Provisioning Templates” and the API documentation.

    • myhost-<%= sequence_hostgroup_param_next("EL7/MyHostgroup", 10, "discovery_host") %>
    • myhost-<%= rand(99999) %>
    • abc-<%= @host.facts['bios_vendor'] %>-<%= rand(99999) %>
    • xyz-<%= %>
    • srv-<%= %>
    • server-<%= @host.ip.gsub('.','-') + '-' + %>

      When creating host name patterns, ensure that the resulting host names are unique, do not start with numbers, and do not contain underscores or dots. A good approach is to use unique information provided by Facter, such as the MAC address, BIOS, or serial ID.

  6. In the Hosts limit field, enter the maximum number of hosts that you can provision with the rule. Enter 0 for unlimited.
  7. In the Priority field, enter a number to set the precedence the rule has over other rules. Rules with lower values have a higher priority.
  8. From the Enabled list, select whether you want to enable the rule.
  9. To set a different provisioning context for the rule, click the Organizations and Locations tabs and select the contexts you want to use.
  10. Click Submit to save your rule.
  11. Navigate to Hosts > Discovered Host and select one of the following two options:

    • From the Discovered hosts list on the right, select Auto-Provision to automatically provisions a single host.
    • On the upper right of the window, click Auto-Provision All to automatically provisions all hosts.

CLI procedure

  1. Create the rule with the hammer discovery-rule create command:

    # hammer discovery-rule create --name "Hypervisor" \
    --search "cpu_count  > 8" --hostgroup "My_Host_Group" \
    --hostname "hypervisor-<%= rand(99999) %>" \
    --hosts-limit 5 --priority 5 --enabled true
  2. Automatically provision a host with the hammer discovery auto-provision command:

    # hammer discovery auto-provision --name "macabcdef123456"

7.7. Implementing PXE-less Discovery

Satellite provides a PXE-less Discovery service that operates without the need for PXE-based services (DHCP and TFTP). You accomplish this using Satellite Server’s Discovery image. Once a discovered node is scheduled for installation, it uses kexec command to reload Linux kernel with OS installer without rebooting the node.


Discovery kexec is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process. For more information about the support scope of Red Hat Technology Preview features, see

Known Issues

The console might freeze during the process. On some hardware, you might experience graphical hardware problems.

PXEless mode

The ISO for the Discovery service resides at /usr/share/foreman-discovery-image/ and is installed using the foreman-discovery-image package.

Attended Use

  1. Copy this media to either a CD, DVD, or a USB stick. For example, to copy to a USB stick at /dev/sdb:

    # dd bs=4M \
    if=/usr/share/foreman-discovery-image/foreman-discovery-image-3.4.4-5.iso \
  2. Insert the Discovery boot media into a bare metal host, start the host, and boot from the media. The Discovery Image displays an option for either Manual network setup or Discovery with DHCP:

    If you select Manual network setup, the Discovery image requests a set of network options. This includes the primary network interface that connects to Satellite Server. This Discovery image also asks for network interface configuration options, such as an IPv4 Address, IPv4 Gateway, and an IPv4 DNS server.

  3. After entering these details, select Next.
  4. If you select Discovery with DHCP, the Discovery image requests only the primary network interface that connects to Satellite Server. It attempts to automatically configure the network interface using a DHCP server, such as one that a Capsule Server provides.
  5. After the primary interface configuration, the Discovery image requests the Server URL, which is the URL of Satellite Server or Capsule Server offering the Discovery service. For example, to use the integrated Capsule on Satellite Server, use the following URL:
  6. Set the Connection type to Proxy, then select Next.
  7. Optional: The Discovery image also provides a set of fields to input Custom facts for the Facter tool to relay back to Satellite Server. These are entered in a name-value format. Provide any custom facts you require and select Confirm to continue.

Satellite reports a successful communication with Satellite Server’s Discovery service. Navigate to Hosts > Discovered Hosts and view the newly discovered host.

For more information about provisioning discovered hosts, see Section 7.5, “Creating Hosts from Discovered Hosts”.

7.8. Unattended Use, Customization, and Image Remastering

You can create a customized Discovery ISO to automate the image configuration process after booting. The Discovery image uses a Linux kernel for the operating system, which passes kernel parameters to configure the discovery service. These kernel parameters include the following entries:

The URL of Capsule Server or Satellite Server providing the Discovery service.
The proxy type. This is usually set to proxy to connect to Capsule Server. This parameter also supports a legacy foreman option, where communication goes directly to Satellite Server instead of a Capsule Server.
The MAC address of the primary interface in the format of AA:BB:CC:DD:EE:FF. This is the interface you aim to use for communicating with Capsule Server. In automated mode, the first NIC (using network identifiers in alphabetical order) with a link is used. In semi-automated mode, a screen appears and requests you to select the correct interface.
fdi.pxip, fdi.pxgw, fdi.pxdns
Manually configures IP address (fdi.pxip), the gateway (fdi.pxgw), and the DNS (fdi.pxdns) for the primary network interface. If your omit these parameters, the image uses DHCP to configure the network interface.
fdi.pxfactname1, fdi.pxfactname2 …​ fdi.pxfactnameN
Use to specify custom fact names.
fdi.pxfactvalue1, fdi.pxfactvalue2 …​ fdi.pxfactvalueN
The values for each custom fact. Each value corresponds to a fact name. For example, fdi.pxfactvalue1 sets the value for the fact named with fdi.pxfactname1.
To set automatic or semi-automatic mode. If set to 0, the image uses semi-automatic mode, which allows you to confirm your choices through a set of dialog options. If set to 1, the image uses automatic mode and proceeds without any confirmation.
By default, the image initializes all network interfaces (value all). When this setting is set to bootif, only the network interface it was network-booted from will be initialized.
By default, the root account is locked. Use this option to set a root password. You can enter both clear and encrypted passwords.
By default, the SSH service is disabled. Set this to 1 or true to enable SSH access.
By default, NetworkManager IPv4 method setting is set to auto. This option overrides it, set it to ignore to disable the IPv4 stack. This option works only in DHCP mode.
By default, NetworkManager IPv6 method setting is set to auto. This option overrides it, set it to ignore to disable the IPv6 stack. This option only works in DHCP mode.
Filenames with extensions to be downloaded and started during boot. For more information, see see Section 7.9, “Extending the Discovery Image”.
TFTP server to use to download extensions from. For more information, see see Section 7.9, “Extending the Discovery Image”.
Number of seconds to wait until the text-user interface is refreshed after the initial discovery attempt. This value defaults to 45 seconds. Increase this value if the status page reports the IP address as N/A.
NetworkManager DHCP timeout. The default value is 300 seconds.
VLAN tagging ID to set for the primary interface.

Using the discovery-remaster Tool to Remaster an OS Image

Satellite Server provides the discovery-remaster tool in the foreman-discovery-image package. This tool remasters the image to include these kernel parameters. To remaster the image, run the discovery-remaster tool. For example:

# discovery-remaster ~/iso/foreman-discovery-image-3.4.4-5.iso \
"fdi.pxip= fdi.pxgw= \
fdi.pxdns= proxy.url= \
proxy.type=proxy fdi.pxfactname1=customhostname fdi.pxfactvalue1=myhost fdi.pxmac=52:54:00:be:8e:8c fdi.pxauto=1"

Copy this media to either a CD, DVD, or a USB stick. For example, to copy to a USB stick at /dev/sdb:

# dd bs=4M \
if=/usr/share/foreman-discovery-image/foreman-discovery-image-3.4.4-5.iso \

Insert the Discovery boot media into a bare metal host, start the host, and boot from the media.

For more information about provisioning discovered hosts, see Section 7.5, “Creating Hosts from Discovered Hosts”.

7.9. Extending the Discovery Image

You can extend the Satellite Discovery image with custom facts, software, or device drivers. You can also provide a compressed archive file containing extra code for the image to use.


  1. Create the following directory structure:

    ├── autostart.d
    │   └──
    ├── bin
    │   └── ntpdate
    ├── facts
    │   └── test.rb
    └── lib
        └── ruby
            └── test.rb
    • The autostart.d directory contains scripts that are executed in POSIX order by the image when it starts, but before the host is registered to Satellite.
    • The bin directory is added to the $PATH variable; you can place binary files in this directory and use them in the autostart scripts.
    • The facts directory is added to the FACTERLIB variable so that custom facts can be configured and sent to Satellite.
    • The lib directory is added to the LD_LIBRARY_PATH variable and lib/ruby is added to the RUBYLIB variable, so that binary files in /bin can be executed correctly.
  2. After creating the directory structure, create a .zip file archive with the following command:

    zip -r .
  3. To inform the Discovery image of the extensions it must use, place your zip files on your TFTP server with the Discovery image, and then update the APPEND line of the PXELinux template with the fdi.zips option where the paths are relative to the TFTP root. For example, if you have two archives at $TFTP/ and $TFTP/boot/, use the following syntax:,boot/

You can append new directives and options to the existing environment variables (PATH, LD_LIBRARY_PATH, RUBYLIB and FACTERLIB). If you want to specify the path explicitly in your scripts, the .zip file contents are extracted to the /opt/extension directory on the image.

You can create multiple .zip files but be aware that they are extracted to the same location on the Discovery image. Files extracted from in later .zip files overwrite earlier versions if they have the same file name.

7.10. Troubleshooting Discovery

If a machine is not listed in the Satellite web UI in Hosts > Discovered Hosts, inspect the following configuration areas to help isolate the error:

  • Navigate to Hosts > Provisioning Templates and redeploy the default PXELinux template using the Build PXE Default button.
  • Verify the pxelinux.cfg/default configuration file on the TFTP Capsule.
  • Ensure adequate network connectivity between hosts, Capsule Server, and Satellite Server.
  • Check the PXELinux template in use and determine the PXE discovery snippet it includes. Snippets are named as follows: pxelinux_discovery, pxegrub_discovery, or pxegrub2_discovery. Verify the proxy.url and proxy.type options in the PXE discovery snippet.
  • Ensure that DNS is working correctly for the discovered nodes, or use an IP address in the proxy.url option in the PXE discovery snippet included in the PXELinux template you are using.
  • Ensure that the DHCP server is delivering IP addresses to the booted image correctly.
  • Ensure the discovered host or virtual machine has at least 1200 MB of memory. Less memory can lead to various random kernel panic errors because the image is extracted in-memory.

For gathering important system facts, use the discovery-debug command. It prints out system logs, network configuration, list of facts, and other information on the standard output. The typical use case is to redirect this output and copy it with the scp command for further investigation.

The first virtual console on the discovered host is reserved for systemd logs. Particularly useful system logs are tagged as follows:

  • discover-host — initial facts upload
  • foreman-discovery — facts refresh, reboot remote commands
  • nm-prepare — boot script which pre-configures NetworkManager
  • NetworkManager — networking information

Use TTY2 or higher to log in to a discovered host. The root account and SSH access are disabled by default, but you can enable SSH and set the root password using the following kernel command-line options in the Default PXELinux template on the APPEND line:

fdi.ssh=1 fdi.rootpw=My_Password
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