TemplateWriting » History » Revision 94
Revision 93 (Sean O'Keeffe, 07/06/2016 09:22 AM) → Revision 94/110 (Dominic Cleal, 08/30/2016 10:21 AM)
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h1. 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.
h2. 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.
h3. 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.
h3. 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.
h3. 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.
h2. Writing templates
Templates can be written using common ERB style templating. Here's an example on using a variable/function:
<pre>
@rootpw --iscrypted <%= root_pass %>@
</pre>
Using a simple conditional:
<pre>
@<%= "selinux --disabled\n" if @osver != 3 -%>@
</pre>
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):
<pre>
<% if @osver == 5 -%>
echo "uses yum"
<% elsif @osver == 4 -%>
echo "uses up2date
<% else -%>
echo "I'm not sure"
<% end -%>
</pre>
h2. Functions and macros:
h3. Generic macros
You should be able to use these macros in any template (Partition tables and Provisioning templates of all kinds)
|_.Name|_.Description|_.Example|
|dns_lookup| Performs a forward or reverse DNS lookup on a supplied name or IP address, Foreman 1.13+ |indent(n)|Indents the block of code by n spaces, useful when using snippet which are not indented | echo <%= dns_lookup('example.com') %> example.com >> /etc/hosts | <pre><code class="ruby"><%= indent 4 do
snippet 'subscription_manager_registration'
end %></code></pre>|
|foreman_server_fqdn| FQDN of Foreman server derived from _foreman_url_ Setting, Foreman 1.12+ | # Template generated at <%= foreman_server_fqdn %> |
|foreman_server_url| Full URL of Foreman server equal to value of _foreman_url_ Setting, Foreman 1.12+ | curl <%= foreman_server_url %>/my_plugin_api |
|foreman_url(kind)| Provides the full URL to a host-rendered template of the given kind, based on _unattended_url_ Setting with fallback to current request headers | foreman_url("provision") => http://HOST/unattended/provision |
|indent(n)|Indents the block of code by n spaces, useful when using snippet which are not indented | <pre><code class="ruby"><%= indent 4 do
snippet 'subscription_manager_registration'
end %></code></pre>|
|snippet(name) | Renders the specified snippet | |
|snippets(file) | Renders the specified snippet found in DB, tries to load it from unattended/snippets/$file directory from hard drive it it's not found in DB | |
|snippet_if_exists(name) | Renders the specified snippet, skip it if it can't be found by name | |
h3. Host specific macros
These macros can be used only when the template is rendered for specific host.
|_.Name|_.Description|_.Example|
|grub_pass |The GRUB password wrapped in md5pass argument | grub_pass # => --md5pass=#{@host.grub_pass} |
|_media_path_ | not used anywhere in built in templates, candidate for removing in Foreman 1.13 | media_path # => /media |
|root_pass |The root password configured for the system| |
|ks_console |A string assembled using the port and baud of the host which can be added to a kernel line | ks_console # => console=ttyS1,9600 |
h3. Variables and snippets
|_.Name|_.Description|_.Example|
|@host.model | The name of the value assigned in Hardware Models. | <notextile><% if @host.model.to_s == 'vmware' %> .. <% end -%></notextile>, <notextile><% if @host.model.to_s == 'xen' %> .. <% end -%></notextile>|
|@host.name |The (full) name of the host| |
|@host.shortname |The (short) name of the host| |
|@host.certname |The SSL certificate name of the host| |
|@host.domain |The domain of the host| |
|@host.ip |The IP address of the host| |
|@host.hostgroup |The hostgroup of the host| <notextile><% if @host.hostgroup.to_s == "Base/Application Servers" -%>...<% end -%></notextile>|
|@host.mac |The HW address of the host| |
|@host.diskLayout |The disklayout of the host (could come from the operating system)| |
|@host.ptable |The disklayout name | <notextile><% if @host.ptable.name == 'Kickstart RHEL default' %> .. <% end %></notextile> |
|@host.puppetmaster |The puppetmaster the host should use | |
|@host.environment |The environment the host should use | |
|@host.location |The location of the host | |
|@host.architecture |The arch of the host (i.e. x86_64)| |
|@host.medium |The assigned OS installation medium (1.10.2+)|
|@host.operatingsystem.name|The operating system name| |
|@host.operatingsystem.major |The major version of the OS| <notextile><% if @host.operatingsystem.major.to_i < 7 %> .. <% end %></notextile> |
|@host.operatingsystem.minor |The minor version of the OS| <notextile><% if @host.operatingsystem.minor.to_i > 2 %> .. <% end %></notextile> |
|@host.operatingsystem.family |The OS Family (I.e. Redhat, Debian, etc.)||
|@host.os.medium_uri(@host) |The url for provisioning (path configured in installation media)|<%= @host.os.medium_uri(@host) %> => http://mirror.os.org/os/|
|@host.param_false?(name) | returns false if host parameter of a given name evaluates to false (e.g. 0, 'no', false, 'false', 'f', off, nil) |<%= @host.param_true?('enable-puppetlabs-repo') %> => true|
|@host.param_true?(name) | returns true if host parameter of a given name evaluates to true (e.g. 1, 'yes', true, 'true', 't', on) |<%= @host.param_true?('enable-puppetlabs-repo') %> => true|
|@host.subnet.mask |The subnet mask of the host||
|@host.subnet.gateway |The gateway of the host||
|@host.subnet.dns_primary |The primary DNS of the host||
|@host.subnet.dns_secondary |The secondary DNS of the host||
|@host.subnet.dhcp|Boolean that render true if a dhcp proxy is configured for this host|<notextile><% if @host.subnet.dhcp %> .. <% else %> .. <% end %></notextile>|
|@host.url_for_boot(:kernel) |Full url to the kernel associated with this host.|Not recommended, as it doesn't interpolate variables, prefer boot_files_uri|
|@host.url_for_boot(:initrd) |Full url to the initrd image associated with this host|Not recommended, as it doesn't interpolate variables|
|@host.operatingsystem.boot_files_uri(@host.medium,@host.architecture) | Full URL to the kernel and initrd, returns an array (1.10.2+) |
|@host.sp_name|The name of the BMC interface ||
|@host.sp_ip|The IP address of the BMC interface ||
|@host.sp_mac|The HW address of the BMC interface ||
|@host.sp_subnet|Subnet of the BMC network ||
|@host.interfaces| Contains an array of all available host interfaces including primary (see networking notes below for changes between Foreman versions) ||
|@host.primary_interface| Returns host's primary interface (1.8+) |it existed in 1.7, returning primary_interface identifier based on imported facts, 1.8+ it returns interface object |
|@host.provision_interface| Returns host's provision interface (1.8+) | returns interface object, see notes below for more details |
|@host.bond_interfaces| Contains an array of all bonds (1.7+) ||
|@host.managed_interfaces| Limit the array to managed (non-BMC nor Bond) interfaces only which are set to be managed (1.7+) ||
|@host.interfaces_with_identifier(['eth0', 'eth1']) | Returns array of interfaces with given identifier (1.7+)||
|@host.interfaces.managed| Limit the array to managed (non-BMC nor Bond) interfaces only (only works if safemode_render=false) ||
|@host.interfaces.bmc| Limit the array to BMC (non-managed) interfaces only (only works if safemode_render=false) ||
|@host.interfaces.size| Number of additional interfaces (either type interface or bmc) (only works if safemode_render=false) |size=1 means a host has two interfaces on 1.7, one interface on 1.8+|
|@host.interfaces.empty|If true host does not have ant interface (only works if safemode_render=false) ||
|@host.facts| Contains a hash of facts from Facter/Ohai etc. (1.7.2+) ||
|@host.facts['ipaddress']| Accessing the 'ipaddress' fact for the host, use @::@ as a separator to access structured facts (1.7.2+) ||
|@host.facts_hash| Contains a hash of facts from Facter/Ohai etc. (only works if safemode_render=false) ||
|@host.facts_hash['ipaddress']| Accessing the 'ipaddress' fact for the host (only works if safemode_render=false) ||
|@host.image_build?| Returns true if the host is provisioned using an image (1.5+)| <notextile><% if @host.image_build? %></notextile> |
|@host.pxe_build?| Returns true if the host is provisioned using the network/PXE (1.5+)| <notextile><% if @host.pxe_build? %></notextile> |
|@provisioning_type|Equal to 'host' or 'hostgroup' depending on type of provisioning (1.6+)| <notextile><% if @provisioning_type == 'hostgroup' %></notextile> |
|@static|Boolean value to determine if the network configuration is static or dynamic|Use <notextile><%= @static ? "static" : "dynamic" %></notextile> in templates|
|@template_name|Name of the template being rendered (1.7+)| <%= @template_name %> |
*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: <pre><% @host.interfaces.each do |i| %> key is <%= i.ip %> <% end %></pre>. To print information for the first interface in the array, try something like: <pre><% myinterface = @host.interfaces.first %> IP: <%= myinterface.ip %> Netmask: <%= myinterface.subnet.mask %> Gateway: <%= myinterface.subnet.gateway %></pre>
*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)
h3. Katello only Variables and snippets
|_.Name|_.Description|_.Example|
|@host.info['parameters']['lifecycle_environment'] |The lifecycle environment of the host| |
|Katello::ActivationKey.find_by_name(@host.info['parameters']['kt_activation_keys']).host_collections<notextile>[1]</notextile>['name'] | The first host collection in the activation key the host is using. (only works if safemode_render=false) |<% if Katello::ActivationKey.find_by_name(@host.info['parameters']['kt_activation_keys').host_collections.select { <notextile>|</notextile>host_collection<notextile>|</notextile> host_collection['name'] == 'MY_HOST_COLLECTION_NAME' } -%>|
h3. Kickstart only variables (Only available for provision templates and "RedHat" Family operating systems):
|_.Name|_.Description|_.Example|
|@osver |The OS Major Version (Same as @host.operatingsystem.major)||
|@arch | The architecture (same as @host.architecture.name) ||
|@mediapath | The full kickstart line to provide the url command.|@mediapath => http://file.example.com/RHEL-5-Server/U5/x86_64/os/|
|@epel |A command which will automatically install the correct version of the epel-release rpm. Use full in a %post script.|@epel => "su -c 'rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm'"|
|@dynamic |true if the parition table being used is a %pre script (has #Dynamic as the first line of the table)|<% if @dynamic -%>|
h3. Preseed attributes (Only available for provision templates and "Debian" Family operating systems)::
|_.Name|_.Description|_.Example|
|@preseed_path |||
|@preseed_server |||
h3. 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.
h3. Compute Resource Specific functions
see [[Compute Resources#Templates]]
h3. Settings
Setting.setting_name
You will need to disable Safemode-Rendering in More->Settings.
h2. 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:
<pre>
@host.ip.rpartition('.')[-1]
</pre>
But this does:
<pre>
@host.ip.split('.').last
</pre>
h2. 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:
<pre>
http://foreman/unattended/provision?spoof=123.321.123.321
</pre>
* 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.