• Table of contents
• Templates
  • Accessing Templates
    • Host-based Rendering
    • Hostgroup-based rendering
    • PXE Menus
  • Writing templates
  • Functions and macros:
    • Generic macros
    • Host specific macros
    • Variables and snippets
    • Katello only Variables and snippets
    • Kickstart only variables (Only available for provision templates and "RedHat" Family operating systems):
    • Preseed attributes (Only available for provision templates and "Debian" Family operating systems)::
    • Host- or Hostgroup parameters
    • Compute Resource Specific functions
    • Settings
  • Ruby methods
  • Troubleshooting

Templates¶

The following functions and macros can be used within templates. These are guaranteed to work via the safemode rendering, to ensure a template can do nothing harmful. With safemode disabled other macros may work, but are not supported at this time.

To enable safemode, set "safemode_render" to "true" in Settings -> Foreman settings. Safemode rendering prevents templates from reading and writing files on the file system or modifying application data within foreman.

Accessing Templates¶

There are two ways to render a template, based on a single host, or based on a Hostgroup. The host or hostgroup provides all the details with which to render the template.

Host-based Rendering¶

Only a single template of each type may be rendered for a system. Foreman determines which template to use following these rules:

1. Only the templates of the appropriate kind and associated with the hosts operating system are considered
2. If a template has a hostgroup/environment combination that matches that of the host, use this template else
3. If a template is associated with the environment of the host, use this template, else
4. Use the first template found associated with the operating system associated with the host.

So essentially, the hostgroup/environment combination is used first, then just the environment, and finally just the operating system of the host.

To access a template of a certain type simply use this url:

/unattended/KIND_NAME

For example: /unattended/provision
would render the provisioning template. The host will be based on the IP Address it is accessed from. To spoof a template simply access the url in this manner:

/unattended/provision?spoof=192.168.0.1

where 192.168.0.1 is the ip address of the system you want to spoof. This allows you to view a template for a particular system from anywhere.

Hostgroup-based rendering¶

Allows any template to be rendered for any host group. When rendering using a hostgroup, @host is actually the hostgroup instead of a defined host. The default values for the hostgroup are used for templated values. This means if a value is not set in the hostgroup, you may get an error when rendering the template. To access a template using a Hostgroup to render, simply use this URL:

/unattended/template/Template Name/Hostgroup Name

For example, a hostgroup of name Finance, and a template named WebServerKickstart could be rendered using the url:

/unattended/template/WebServerKickstart/Finance

When building the default PXE template (from the Provisioning Templates page), any host group with the operating system, installation media and architecture set, plus provisioning templates with the host group set on the Associations tab will be listed at the bottom of the menu.

PXE Menus¶

PXE Menus can be deployed to smart proxies from the Provisioning Templates list page (/templates/provisioning_templates). All provisioning templates will be added with each of their hostgroup combinations (see above). For example if the template "WebServerKickstart" is associated to the Hostgroup1/Production, Hostgroup2/Production, and Hostgroup2/Testing combinations, the template would only be added twice. Once for WebServerKickstart-Hostgroup1 and WebServerKickstart-Hostgroup2.

Note that you can use only macros that are not host specific since this global PXE template is not specific to one host.

Writing templates¶

Templates can be written using common ERB style templating. Here's an example on using a variable/function:

@rootpw --iscrypted <%= root_pass %>@

Using a simple conditional:

@<%= "selinux --disabled\n" if @osver != 3 -%>@

This would include a line to disable selinux if the operating system version is not 3 (since Selinux isn't supported on RHEL 3)

Another way to do conditional (with if/elsif/else):

<% if @osver == 5 -%>
 echo "uses yum" 
<% elsif @osver == 4 -%>
 echo "uses up2date
<% else -%>
 echo "I'm not sure" 
<% end -%>

Functions and macros:¶

Generic macros¶

You should be able to use these macros in any template (Partition tables and Provisioning templates of all kinds)

<%= indent 4 do
    snippet 'subscription_manager_registration'
end %>

Host specific macros¶

These macros can be used only when the template is rendered for specific host.

Variables and snippets¶

NOTE: For PXELinux templates in 0.4 or older only leave off the '@host.' from the above as it is currently generated slightly different from everything else.

NOTE: The interface array can be parsed this way:

<% @host.interfaces.each do |i| %> key is <%= i.ip %> <% end %>

<% myinterface = @host.interfaces.first %> IP: <%= myinterface.ip %> Netmask: <%= myinterface.subnet.mask %> Gateway: <%= myinterface.subnet.gateway %>

NOTE: Some variables can't be accessed while safemode is enabled. Disable via safemode_render in More > Settings, though be aware this enables arbitrary code to be added to templates. Some are being whitelisted via #2948.

NOTE: You may need to add "&static=yes" to the foreman_url to use the @static parameter in templates (see KickstartStatic).

NOTE: A lot of networking functions changed their meaning between 1.7 and 1.8 releases. In 1.7, primary interface used to be part of host object so it was not part of '@host.interfaces'. Also it could be detected by '@host.has_primary_interface?' which was removed in 1.8. For more advanced example of using networking functions, see kickstart_networking_setup.erb provisioning template snippet.

NOTE: If you get interface object as a returning value of some function (e.g. primary_interface or interfaces.first) it is evaluated to its DNS name by default. You can easily get to other attributes of such interface, e.g. @host.primary_interface.identifier or @host.primary_interface.mac. Valid attributes include: "managed?", "subnet" (returns subnet object), "virtual?", "physical?", "mac", "ip", "identifier", "attached_to", "link", "tag", "domain" (returns domain object), "vlanid", "bond_options", "attached_devices", "mode", "attached_devices_identifiers", "primary", "provision", "alias?", "inheriting_mac" (if it's virtual it inherits the mac from attached_to device)

Katello only Variables and snippets¶

Kickstart only variables (Only available for provision templates and "RedHat" Family operating systems):¶

Preseed attributes (Only available for provision templates and "Debian" Family operating systems)::¶

Host- or Hostgroup parameters¶

@host.params['parameter_name']

If you need to test if a parameter contains a boolean true/false value, there are two helpers that will help:

@host.param_true?('parameter_name')
@host.param_false?('parameter_name')

These check the parameter is a true/false/on/off/1/0 string.

Hint: For Foreman older than 1.0 you have to disable Safemode-Rendering in More->Settings.

Compute Resource Specific functions¶

see Compute Resources

Settings¶

Setting.setting_name

You will need to disable Safemode-Rendering in More->Settings.

Ruby methods¶

The most common methods on Ruby's core classes should be allowed (split, gsub, to_i, blank?, etc). A full list is in the Safemode Gem: https://github.com/svenfuchs/safemode/blob/master/lib/safemode/core_jails.rb#L33

To avoid turning off safemode, consider alternative ways of writing your ruby code. For example this would not work in the default Jail:

@host.ip.rpartition('.')[-1]

But this does:

@host.ip.split('.').last

Troubleshooting¶

Kickstart/preseed files are all generated dynamically based on the setting of each host in Foreman, things like partition tables and root password can be unique per server.

If you are having issues with a system building from a template or a system is unable to retrieve a template you can see the kickstart/preseed template result using your browser. If your system failed to retrieve the kickstart file it may be due to the fact that the template build failed.

Use the spoof parameter by pointing your browser to a url similar to:

http://foreman/unattended/provision?spoof=123.321.123.321

• 123.321.123.321 is the hosts IP Address (the one you want to build).
• usually you want to see the page source, the browser might display the file in html which will result in hard to read output.
• the completed template will be displayed or any errors that were encountered while the template was being built.