ERB templates | AutoYaST Guide | SUSE Linux Enterprise Micro 5.0

documentation.suse.com › SUSE Linux Enterprise Micro Documentation › AutoYaST Guide › Managing mass installations with dynamic profiles › ERB templates

Applies to SUSE Linux Enterprise Micro 5.0

7 ERB templates #Edit source

7.1 What is ERB?
7.2 Template helpers

ERB templates allow embedding some Ruby code within the profile to modify it during the installation. With this approach, you can inspect the system and adjust the profile by setting values, adding or skipping sections, etc.

To activate the ERB processing, the profile must have the extension .erb (for example, autoyast.xml.erb). Hence, it is not possible to combine rules/classes and ERB templates.

7.1 What is `ERB`? #Edit source

ERB stands for Embedded Ruby and allows using the power of the Ruby programming language to generate different kind of contents. With ERB, you can include some Ruby code in your profiles to adapt them at runtime depending on the installation system.

When using ERB, the Ruby code is enclosed between <% and > signs. If you want the output of the command to be included in the resulting profile, you simply need to add an equal sign (=).

Example 7.1: Including a file using ERB #

<bootloader>
  <% require "open-uri" %>
  <%= URI.open("http://192.168.1.1/profiles/bootloader-common.xml").read %>
</bootloader>

AutoYaST offers a small set of helper functions to retrieve information from the underlying system, like disks or network_cards. You can check the list of helpers and their values in the Section 7.2, “Template helpers” section.

7.2 Template helpers #Edit source

Template helpers are sets of Ruby methods that can be used in the profiles to retrieve information about the installation system.

7.2.1 `disks` #Edit source

The disks helper returns a list of the detected disks. Each element of the list contains some basic information like the device name or the size.

Key	Type	Value
`:device`	String	Device kernel name (for example, `sda`).
`:model`	String	Disk model
`:serial`	String	Serial number
`:size`	Integer	Disk size (in bytes)
`:udev_names`	Array<String>	List of disk udev names. You can use any of them to refer to the device.
`:vendor`	String	Disk vendor's name

The profile in the example below installs the system on the largest disk. It sorts the list of existing disks by size and takes the last one. Then it uses the :device key as value for the device element.

Example 7.2: Using the largest disk #

<partitioning t="list">
  <drive>
    <% disk = disks.sort_by { |d| d[:size] }.last %> <!-- find the largest disk -->
    <device><%= disk[:device] %></device> <!-- print the disk device name -->
    <initialize t="boolean">true</initialize>
    <use>all</use>
  </drive>
</partitioning>

7.2.2 `network_cards` #Edit source

The network_cards helper returns a list of network cards, including their names, status information (for example, if they are connected or not).

Key	Type	Value
`:device`	String	Device name (for example, `eth0` or `enp3s0`)
`:mac`	String	MAC address
`:active`	Boolean	Whether the device is active or not
`:link`	Boolean	Whether the device is connected or not
`:vendor`	String	Disk vendor's name

The following example finds the first network card that is connected to the network and configures it to use DHCP.

Example 7.3: Configure the connected network cards #

<interfaces t="list">
  <% with_link = netword_cards.sort_by { |n| n[:name] }.find { |n| n[:link] } %>
  <% if with_link %>
    <interface>
      <device><%= with_link[:device] %></device>
      <startmode>auto</startmode>
      <bootproto>dhcp</bootproto>
      </interface>
  <% end >
</interfaces>

7.2.3 `os_release` #Edit source

The os_release helper returns the operating system information, which is included in the /etc/os-release file.

Key	Type	Value
`:id`	String	Distribution ID (for example, `sles`, `opensuse-tumbleweed`)
`:name`	String	Distribution name (for example, `SLES` or `openSUSE Tumbleweed`)
`:version`	String	Distribution version (for example, `15.2`)

You might use this information to decide which product to install, using pretty much the same profile for all of them (SLE or openSUSE distributions).

Example 7.4: Reusing the same profile for different distributions #

<products t="list">
  <% if os_release[:id] == 'sle' %>
  <product>SLES</product>
  <% else %<
  <product>openSUSE</product>
  <% end %<
</products>

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