cdist-manifest - (Re-)Use types

Manifests are used to define which objects to create. Objects are instances of types, like in object oriented programming languages. An object is represented by the combination of type + slash + object name: file/etc/cdist-configured is an object of the type file with the name etc/cdist-configured.

All available types can be found in the cdist/conf/type/ directory, use ls cdist/conf/type to get the list of available types. If you have setup the MANPATH correctly, you can use man cdist-reference to access the reference with pointers to the manpages.

Types in manifests are used like normal command line tools. Let’s have a look at an example:

# Create object of type __package with the parameter state = absent
__package apache2 --state absent

# Same with the __directory type
 __directory /tmp/cdist --state present

These two lines create objects, which will later be used to realise the configuration on the target host.

Manifests are executed locally as a shell script using /bin/sh -e. The resulting objects are stored in an internal database.

The same object can be redefined in multiple different manifests as long as the parameters are exactly the same.

In general, manifests are used to define which types are used depending on given conditions.

Cdist knows about two types of manifests: The initial manifest and type manifests. The initial manifest is used to define, which configurations to apply to which hosts. The type manifests are used to create objects from types. More about manifests in types can be found in cdist-type(7).

The initial manifest is the entry point for cdist to find out, which objects to configure on the selected host. Cdist expects the initial manifest at cdist/conf/manifest/init.

Within this initial manifest you define, which objects should be created on which host. To distinguish between hosts, you can use the environment variable __target_host. Let’s have a look at a simple example:

__cdistmarker

case "$__target_host" in
   localhost)
        __directory /home/services/kvm-vm --parents yes
   ;;
esac

This manifest says: Independent of the host, always use the type __cdistmarker, which creates the file /etc/cdist-configured, with the timestamp as content. The directory /home/services/kvm-vm, including all parent directories, is only created on the host localhost.

As you can see, there is no magic involved, the manifest is simple shell code that utilises cdist types. Every available type can be executed like a normal command.

If you want to split up your initial manifest, you can create other shell scripts in cdist/conf/manifest/ and include them in cdist/conf/manifest/init. Cdist provides the environment variable __manifest to reference to the directory containing the initial manifest (see cdist-reference(7)).

The following example would include every file with a .sh suffix:

# Include *.sh
for manifest in $__manifest/*.sh; do
    # And source scripts into our shell environment
    . "$manifest"
done

If you want to describe that something requires something else, just setup the variable "require" to contain the requirements. Multiple requirements can be added white space separated.

# No dependency
__file /etc/cdist-configured

# Require above object
require="__file/etc/cdist-configured" __link /tmp/cdist-testfile \
   --source /etc/cdist-configured  --type symbolic

# Require two objects
require="__file/etc/cdist-configured __link/tmp/cdist-testfile" \
   __file /tmp/cdist-another-testfile

All objects that are created in a type manifest are automatically required from the type that is calling them. This is called "autorequirement" in cdist jargon.

The initial manifest may for instance contain the following code:

# Always create this file, so other sysadmins know cdist is used.
__file /etc/cdist-configured

case "$__target_host" in
   my.server.name)
      __directory /root/bin/
      __file /etc/issue.net --source "$__manifest/issue.net
   ;;
esac

The manifest of the type "nologin" may look like this:

__file /etc/nologin --source "$__type/files/default.nologin"

This example makes use of dependencies:

# Ensure that lighttpd is installed
__package lighttpd --state present
# Ensure that munin makes use of lighttpd instead of the default webserver
# package as decided by the package manager
require="__package/lighttpd" __package munin --state present

Copyright (C) 2010-2012 Nico Schottelius. Free use of this software is granted under the terms of the GNU General Public License version 3 (GPLv3).