cdist-backup/doc/man/man7/cdist-tutorial.text

cdist-tutorial(7)
=================
Nico Schottelius <nico-cdist--@--schottelius.org>


NAME
----
cdist-tutorial - a guided introduction into cdist


INTRODUCTION
------------
This tutorial is aimed at people learning cdist and shows
typical approaches as well as gives an easy start into
the world of configuration management.

This tutorial assumes you are configuring **localhost**, because
it is always available. Just replace **localhost** with your target
host for real life usage.



QUICK START - GET YOUR HANDS DIRTY NOW
--------------------------------------
For those who just want to configure a system with the
cdist configuration management and do not need (or want)
to understand everything.

Cdist uses **ssh** for communication and transportation
and usually logs into the **target host** as the
**root** user. So you need to configure the **ssh server**
of the target host to allow root logins: Edit
the file **/etc/ssh/sshd_config** and add one of the following
lines:

--------------------------------------------------------------------------------
# Allow login only via public key
PermitRootLogin without-password

# Allow login via password and public key
PermitRootLogin yes
--------------------------------------------------------------------------------

As cdist uses ssh intensively, it is recommended to setup authentication
with public keys:

--------------------------------------------------------------------------------
# Generate pubkey pair as a normal user
ssh-keygen

# Copy pubkey over to target host
ssh-copy-id root@localhost
--------------------------------------------------------------------------------

Have a look at ssh-agent(1) and ssh-add(1) on how to cache the password for
your public key.  Usually it looks like this:

--------------------------------------------------------------------------------
# Start agent and export variables
eval `ssh-agent`

# Add keys (requires password for every identity file)
ssh-add
--------------------------------------------------------------------------------

At this point you should be able to ***ssh root@localhost*** without
re-entering the password. If something failed until here, ensure that
all steps went successfully and you have read and understood the
documentation.

As soon as you are able to login without passwort to the target host,
we can use cdist to configure it. You can copy and paste the following
code into your shell to get started and configure localhost:

--------------------------------------------------------------------------------
# Get cdist
git clone git://git.schottelius.org/cdist

# Create manifest (maps configuration to host(s)
cd cdist
echo '__file /etc/cdist-configured' > conf/manifest/init

# Configure localhost in verbose mode
./bin/cdist config -v localhost

# Find out that cdist created /etc/cdist-configured
ls -l /etc/cdist-configured
--------------------------------------------------------------------------------

That's it, you've successfully used cdist to configure your first host!
Continue reading the next sections, to understand what you did and how
to create a more sophisticated configuration.

The file 'conf/manifest/init' is usually the entry point for cdist,
to find out what to configure on which host. All manifests are
essentially shell scripts. Every manifest can use the types known to
cdist, which are usually underline prefixed (__).



DEFINE STATE IN THE INITIAL MANIFEST
------------------------------------
The **initial manifest** is the entry point for cdist to find out, which
**objects** to configure on the selected host. Objects are instances of
**types**, like in object orientated programming. An object is represented
by the type + slash + object name: ***__file/etc/cdist-configured*** is an
object of the type ***__file*** with the name ***etc/cdist-configured***.

Cdist searches for the initial manifest at **conf/manifest/init** and
executes it as a shell script using **/bin/sh -e**.

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:

--------------------------------------------------------------------------------
__file /etc/cdist-configured

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

This manifest says: Independent of the host, always create the (empty) file
***/etc/cdist-configured***, but create the directory ***/home/services/kvm-vm***,
including all parent directories, only on the host ***localhost***.

As you can see, there is no magic involved, the manifest is simple shell code that
utilises cdist types.


PARTS BELOW HERE ARE TO-BE-DONE


MORE ABOUT TYPES AND OBJECTS
----------------------------
All available types in cdist can be called like normal executables. 


USING SOME BASIC TYPES
----------------------
what is a type, how to use it,


CREATING YOUR FIRST OWN TYPE
----------------------------
<with object id? or signleton here already>


USE A TYPE TO BUNDLE FUNCTIONALITY
----------------------------------


USING EXPLORERS
---------------
global, type explorer


DEBUGGING YOUR TYPES
--------------------
__debug::
   If this variable is setup, cdist runs in debug mode.
   You can use this information, to only output stuff in debug
   mode as well.
   Available for: initial manifest, type manifest, gencode, code




BRANCHES IN HERE?
------------

TUNING CDIST
------------

- speedup processing with ControlMaster option of
ssh


SEE ALSO
--------
cdist(1), cdist-type(7), cdist-stages(7)