257 lines
9.5 KiB
ReStructuredText
257 lines
9.5 KiB
ReStructuredText
Manifest
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========
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Description
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-----------
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Manifests are used to define which objects to create.
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Objects are instances of **types**, like in object oriented programming languages.
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An object is represented by the combination of
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**type + slash + object name**: **\__file/etc/cdist-configured** is an
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object of the type **__file** with the name **etc/cdist-configured**.
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All available types can be found in the **cdist/conf/type/** directory,
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use **ls cdist/conf/type** to get the list of available types. If you have
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setup the MANPATH correctly, you can use **man cdist-reference** to access
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the reference with pointers to the manpages.
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Types in manifests are used like normal command line tools. Let's have a look
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at an example::
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# Create object of type __package with the parameter state = absent
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__package apache2 --state absent
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# Same with the __directory type
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__directory /tmp/cdist --state present
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These two lines create objects, which will later be used to realise the
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configuration on the target host.
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Manifests are executed locally as a shell script using **/bin/sh -e**.
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The resulting objects are stored in an internal database.
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The same object can be redefined in multiple different manifests as long as
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the parameters are exactly the same.
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In general, manifests are used to define which types are used depending
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on given conditions.
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Initial and type manifests
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--------------------------
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Cdist knows about two types of manifests: The initial manifest and type
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manifests. The initial manifest is used to define, which configurations
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to apply to which hosts. The type manifests are used to create objects
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from types. More about manifests in types can be found in `cdist type <cdist-type.html>`_.
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Define state in the initial manifest
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------------------------------------
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The **initial manifest** is the entry point for cdist to find out, which
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**objects** to configure on the selected host.
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Cdist expects the initial manifest at **cdist/conf/manifest/init**.
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Within this initial manifest you define which objects should be
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created on which host. To distinguish between hosts, you can use the
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environment variable **__target_host** and/or **__target_hostname** and/or
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**__target_fqdn**. Let's have a look at a simple example::
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__cdistmarker
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case "$__target_host" in
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localhost)
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__directory /home/services/kvm-vm --parents yes
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;;
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esac
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This manifest says: Independent of the host, always use the type
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**__cdistmarker**, which creates the file **/etc/cdist-configured**,
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with the timestamp as content.
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The directory **/home/services/kvm-vm**, including all parent directories,
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is only created on the host **localhost**.
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As you can see, there is no magic involved, the manifest is simple shell code that
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utilises cdist types. Every available type can be executed like a normal
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command.
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Splitting up the initial manifest
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---------------------------------
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If you want to split up your initial manifest, you can create other shell
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scripts in **cdist/conf/manifest/** and include them in **cdist/conf/manifest/init**.
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Cdist provides the environment variable **__manifest** to reference
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the directory containing the initial manifest (see `cdist reference <cdist-reference.html>`_).
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The following example would include every file with a **.sh** suffix::
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# Include *.sh
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for manifest in $__manifest/*.sh; do
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# And source scripts into our shell environment
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. "$manifest"
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done
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Dependencies
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------------
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If you want to describe that something requires something else, just
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setup the variable "require" to contain the requirements. Multiple
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requirements can be added white space separated.
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::
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1 # No dependency
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2 __file /etc/cdist-configured
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3
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4 # Require above object
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5 require="__file/etc/cdist-configured" __link /tmp/cdist-testfile \
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6 --source /etc/cdist-configured --type symbolic
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7
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8 # Require two objects
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9 require="__file/etc/cdist-configured __link/tmp/cdist-testfile" \
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10 __file /tmp/cdist-another-testfile
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Above the "require" variable is only set for the command that is
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immediately following it. Dependencies should always be declared that way.
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On line 4 you can see that the instantiation of a type "\__link" object needs
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the object "__file/etc/cdist-configured" to be present, before it can proceed.
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This also means that the "\__link" command must make sure, that either
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"\__file/etc/cdist-configured" already is present, or, if it's not, it needs
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to be created. The task of cdist is to make sure, that the dependency will be
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resolved appropriately and thus "\__file/etc/cdist-configured" be created
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if necessary before "__link" proceeds (or to abort execution with an error).
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If you really need to make all types depend on a common dependency, you can
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export the "require" variable as well. But then, if you need to add extra
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dependencies to a specific type, you have to make sure that you append these
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to the globally already defined one.
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::
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# First of all, update the package index
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__package_update_index
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# Upgrade all the installed packages afterwards
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require="__package_update_index" __package_upgrade_all
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# Create a common dependency for all the next types so that they get to
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# be executed only after the package upgrade has finished
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export require="__package_upgrade_all"
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# Ensure that lighttpd is installed after we have upgraded all the packages
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__package lighttpd --state present
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# Ensure that munin is installed after lighttpd is present and after all
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# the packages are upgraded
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require="$require __package/lighttpd" __package munin --state present
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All objects that are created in a type manifest are automatically required
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from the type that is calling them. This is called "autorequirement" in
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cdist jargon.
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You can find a more in depth description of the flow execution of manifests
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in `cdist execution stages <cdist-stages.html>`_ and of how types work in `cdist type <cdist-type.html>`_.
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Create dependencies from execution order
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-----------------------------------------
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You can tell cdist to execute all types in the order in which they are created
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in the manifest by setting up the variable CDIST_ORDER_DEPENDENCY.
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When cdist sees that this variable is setup, the current created object
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automatically depends on the previously created object.
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It essentially helps you to build up blocks of code that build upon each other
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(like first creating the directory xyz than the file below the directory).
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Read also about `perils of CDIST_ORDER_DEPENDENCY <cdist-best-practice.html#perils-of-cdist-order-dependency>`_.
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Overrides
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---------
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In some special cases, you would like to create an already defined object
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with different parameters. In normal situations this leads to an error in cdist.
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If you wish, you can setup the environment variable CDIST_OVERRIDE
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(any value or even empty is ok) to tell cdist, that this object override is
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wanted and should be accepted.
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ATTENTION: Only use this feature if you are 100% sure in which order
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cdist encounters the affected objects, otherwise this results
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in an undefined situation.
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If CDIST_OVERRIDE and CDIST_ORDER_DEPENDENCY are set for an object,
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CDIST_ORDER_DEPENDENCY will be ignored, because adding a dependency in case of
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overrides would result in circular dependencies, which is an error.
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Examples
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--------
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The initial manifest may for instance contain the following code:
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.. code-block:: sh
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# Always create this file, so other sysadmins know cdist is used.
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__file /etc/cdist-configured
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case "$__target_host" in
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my.server.name)
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__directory /root/bin/
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__file /etc/issue.net --source "$__manifest/issue.net
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;;
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esac
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The manifest of the type "nologin" may look like this:
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.. code-block:: sh
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__file /etc/nologin --source "$__type/files/default.nologin"
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This example makes use of dependencies:
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.. code-block:: sh
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# Ensure that lighttpd is installed
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__package lighttpd --state present
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# Ensure that munin makes use of lighttpd instead of the default webserver
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# package as decided by the package manager
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require="__package/lighttpd" __package munin --state present
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How to override objects:
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.. code-block:: sh
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# for example in the initial manifest
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# create user account foobar with some hash for password
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__user foobar --password 'some_fancy_hash' --home /home/foobarexample
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# ... many statements and includes in the manifest later ...
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# somewhere in a conditionally sourced manifest
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# (e.g. for example only sourced if a special application is on the target host)
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# this leads to an error ...
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__user foobar --password 'some_other_hash'
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# this tells cdist, that you know that this is an override and should be accepted
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CDIST_OVERRIDE=yes __user foobar --password 'some_other_hash'
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# it's only an override, means the parameter --home is not touched
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# and stays at the original value of /home/foobarexample
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Dependencies defined by execution order work as following:
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.. code-block:: sh
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# Tells cdist to execute all types in the order in which they are created ...
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export CDIST_ORDER_DEPENDENCY=on
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__sample_type 1
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require="__some_type_somewhere/id" __sample_type 2
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__example_type 23
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# Now this types are executed in the creation order until the variable is unset
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unset CDIST_ORDER_DEPENDENCY
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# all now following types cdist makes the order ..
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__not_in_order_type 42
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# how it works :
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# this lines above are translated to:
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__sample_type 1
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require="__some_type_somewhere/id __sample_type/1" __sample_type 2
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require="__sample_type/2" __example_type 23
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__not_in_order_type 42
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