Provided by: cdist_4.0.0~pre3-2_all 
NAME
cdist-type - Functionality bundled
SYNOPSIS
__TYPE ID --parameter value [--parameter value ...]
__TYPE --parameter value [--parameter value ...] (for singletons)
DESCRIPTION
Types are the main component of cdist and define functionality. If you use cdist, you’ll write a type for
every functionality you would like to use.
HOW TO USE A TYPE
You can use types from the initial manifest or the type manifest like a normal shell command:
# Creates empty file /etc/cdist-configured
__file /etc/cdist-configured --type file
# Ensure tree is installed
__package tree --state installed
A list of supported types can be found in the cdist-reference(7) manpage.
SINGLETON TYPES
If a type is flagged as a singleton, it may be used only once per host. This is useful for types which
can be used only once on a system. Singleton types do not take an object name as argument.
Example:
# __issue type manages /etc/issue
__issue
# Probably your own type - singletons may use parameters
__myfancysingleton --colour green
HOW TO WRITE A NEW TYPE
A type consists of
• parameter (optional)
• manifest (optional)
• singleton (optional)
• explorer (optional)
• gencode (optional)
Types are stored below cdist/conf/type/. Their name should always be prefixed with two underscores (__)
to prevent collisions with other executables in $PATH.
To implement a new type, create the directory cdist/conf/type/__NAME.
DEFINING PARAMETERS
Every type consists of required, optional and boolean parameters, which must each be declared in a
newline separated file in parameter/required, parameter/required_multiple, parameter/optional,
parameter/optional_multiple and parameter/boolean. Parameters which are allowed multiple times should be
listed in required_multiple or optional_multiple respectively. All other parameters follow the standard
unix behaviour "the last given wins". If either is missing, the type will have no required, no optional,
no boolean or no parameters at all.
Default values for optional parameters can be predefined in parameter/default/<name>.
Example:
echo servername >> cdist/conf/type/__nginx_vhost/parameter/required
echo logdirectory >> cdist/conf/type/__nginx_vhost/parameter/optional
echo loglevel >> cdist/conf/type/__nginx_vhost/parameter/optional
mkdir cdist/conf/type/__nginx_vhost/parameter/default
echo warning > cdist/conf/type/__nginx_vhost/parameter/default/loglevel
echo server_alias >> cdist/conf/type/__nginx_vhost/parameter/optional_multiple
echo use_ssl >> cdist/conf/type/__nginx_vhost/parameter/boolean
USING PARAMETERS
The parameters given to a type can be accessed and used in all type scripts (e.g manifest, gencode-,
explorer/). Note that boolean parameters are represented by file existence. File exists → True, file does
not exist → False
Example: (e.g. in cdist/conf/type/__nginx_vhost/manifest)
# required parameter
servername="$(cat "$__object/parameter/servername")"
# optional parameter
if [ -f "$__object/parameter/logdirectory" ]; then
logdirectory="$(cat "$__object/parameter/logdirectory")"
fi
# optional parameter with predefined default
loglevel="$(cat "$__object/parameter/loglevel")"
# boolean parameter
if [ -f "$__object/parameter/use_ssl" ]; then
# file exists -> True
# do some fancy ssl stuff
fi
# parameter with multiple values
if [ -f "$__object/parameter/server_alias" ]; then
for alias in $(cat "$__object/parameter/server_alias"); do
echo $alias > /some/where/usefull
done
fi
INPUT FROM STDIN
Every type can access what has been written on stdin when it has been called. The result is saved into
the stdin file in the object directory.
Example use of a type: (e.g. in cdist/conf/type/__archlinux_hostname)
__file /etc/rc.conf --source - << eof
...
HOSTNAME="$__target_host"
...
eof
If you have not seen this syntax (<< eof) before, it may help you to read about "here documents".
In the __file type, stdin is used as source for the file, if - is used for source:
if [ -f "$__object/parameter/source" ]; then
source="$(cat "$__object/parameter/source")"
if [ "$source" = "-" ]; then
source="$__object/stdin"
fi
....
WRITING THE MANIFEST
In the manifest of a type you can use other types, so your type extends their functionality. A good
example is the __package type, which in a shortened version looks like this:
os="$(cat "$__global/explorer/os")"
case "$os" in
archlinux) type="pacman" ;;
debian|ubuntu) type="apt" ;;
gentoo) type="emerge" ;;
*)
echo "Don't know how to manage packages on: $os" >&2
exit 1
;;
esac
__package_$type "$@"
As you can see, the type can reference different environment variables, which are documented in
cdist-reference(7).
Always ensure the manifest is executable, otherwise cdist will not be able to execute it. For more
information about manifests see cdist-manifest(7).
SINGLETON - ONE INSTANCE ONLY
If you want to ensure that a type can only be used once per target, you can mark it as a singleton: Just
create the (empty) file "singleton" in your type directory:
touch cdist/conf/type/__NAME/singleton
This will also change the way your type must be called:
__YOURTYPE --parameter value
As you can see, the object ID is omitted, because it does not make any sense, if your type can be used
only once.
THE TYPE EXPLORERS
If a type needs to explore specific details, it can provide type specific explorers, which will be
executed on the target for every created object.
The explorers are stored under the "explorer" directory below the type. It could for instance contain
code to check the md5sum of a file on the client, like this (shortened version from the type __file):
if [ -f "$__object/parameter/destination" ]; then
destination="$(cat "$__object/parameter/destination")"
else
destination="/$__object_id"
fi
if [ -e "$destination" ]; then
md5sum < "$destination"
fi
WRITING THE GENCODE SCRIPT
There are two gencode scripts: gencode-local and gencode-remote. The output of gencode-local is executed
locally, whereas the output of gencode-remote is executed on the target. The gencode scripts can make use
of the parameters, the global explorers and the type specific explorers.
If the gencode scripts encounters an error, it should print diagnostic messages to stderr and exit
non-zero. If you need to debug the gencode script, you can write to stderr:
# Debug output to stderr
echo "My fancy debug line" >&2
# Output to be saved by cdist for execution on the target
echo "touch /etc/cdist-configured"
VARIABLE ACCESS FROM THE GENERATED SCRIPTS
In the generated scripts, you have access to the following cdist variables
• __object
• __object_id
but only for read operations, means there is no back copy of this files after the script execution.
So when you generate a script with the following content, it will work:
if [ -f "$__object/parameter/name" ]; then
name="$(cat "$__object/parameter/name")"
else
name="$__object_id"
fi
HINTS FOR TYPEWRITERS
It must be assumed that the target is pretty dumb and thus does not have high level tools like ruby
installed. If a type requires specific tools to be present on the target, there must be another type that
provides this tool and the first type should create an object of the specific type.
If your type wants to save temporary data, that may be used by other types later on (for instance file),
you can save them in the subdirectory "files" below $object (but you must create it yourself). cdist will
not touch this directory.
If your type contains static files, it’s also recommended to place them in a folder named "files" within
the type (again, because cdist guarantees to never ever touch this folder).
HOW TO INCLUDE A TYPE INTO UPSTREAM CDIST
If you think your type may be useful for others, ensure it works with the current master branch of cdist
and have a look at cdist-hacker(7) on how to submit it.
SEE ALSO
• cdist-explorer(7) • cdist-hacker(7) • cdist-stages(7) • cdist-tutorial(7)
COPYING
Copyright (C) 2011-2012 Nico Schottelius. Free use of this software is granted under the terms of the GNU
General Public License version 3 (GPLv3).
AUTHOR
Nico Schottelius <nico-cdist--@--schottelius.org>
Author.
04/07/2016 CDIST-TYPE(7)