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11.5. Cobbler Templates
Within the RHN Satellite web interface, there are facilities to create variables for use with kickstart distributions and profiles. For example, to create a kickstart profile variable, refer to Section 7.4.9.3.3, “Kickstart Details ⇒ Variables”.
Kickstart variables are a part of an infrastructural change in Satellite to support templating in kickstart files. In the context of kickstart files, templates are files that hold descriptions used to build actual kickstart files, rather than creating specific kickstarts.
These templates are then shared by various profiles and systems that have their own variables and corresponding values. These variables modify the templates and software called a template engine parses the template and variable data into a usable kickstart file. Cobbler uses an advanced template engine called Cheetah that provides support for templates, variables, and snippets.
Advantages of using templates include:
- Robust features that allow administrators to create and manage large amounts of profiles or systems without duplication of effort or manually creating kickstarts for every unique situation
- While templates can become complex and involve loops, conditionals and other enhanced features and syntax, it can also be used simply to make kickstart files without such complexity.
11.5.1. Using Templates
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Kickstart templates can have static values for certain common items such as PXE image filenames, subnet addresses, and common paths such as
/etc/sysconfig/network-scripts/. However, where templates differ from standard kickstart files are in their use of variables.
For example, a standard kickstart file may have a networking passage that looks similar to the following
network --device=eth0 --bootproto=static --ip=192.168.100.24 --netmask=255.255.255.0 --gateway=192.168.100.1 --nameserver=192.168.100.2
network --device=eth0 --bootproto=static --ip=192.168.100.24 --netmask=255.255.255.0 --gateway=192.168.100.1 --nameserver=192.168.100.2
However, in a kickstart template file, the networking passage may look similar to the following:
network --device=$net_dev --bootproto=static --ip=$ip_addr --netmask=255.255.255.0 --gateway=$my_gateway --nameserver=$my_nameserver
network --device=$net_dev --bootproto=static --ip=$ip_addr --netmask=255.255.255.0 --gateway=$my_gateway --nameserver=$my_nameserver
These variables will be substituted with the values set in your kickstart profile variables or in your system detail variables. If there are the same variables defined in both the profile and the system detail, then the system variable takes precedence.
For more information about kickstart templates, refer to the Cobbler project page at the following URL:
11.5.2. Kickstart Snippets
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If you have common configurations that are the same across all kickstart templates and profiles, you can utilize the Snippets feature of Cobbler to take advantage of code reuse.
Kickstart snippets are sections of kickstart code that can be called by a
$SNIPPET() function that will be parsed by Cobbler and substitute that function call with the contents of the snippet.
For example, if you had a common hard drive partition configuration for all servers, such as:
You could take that snippet, save it to a file (such as
my_partition), and place the file in /var/lib/cobbler/snippets/ so that Cobbler can access them.
You can then use the snippet by using the
$SNIPPET() function in your kickstart templates. For example:
$SNIPPET('my_partition')
$SNIPPET('my_partition')
Wherever you invoke that function, the Cheetah parser will substitute the function with the snippet of code contained in the
my_partition file.
For more information about kickstart snippets, refer to the Cobbler project page at the following URL:
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