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 password to localhost,
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.



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 languages.
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:

--------------------------------------------------------------------------------
__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. Use **ls conf/type** to get a list of available types. If you have
setup the MANPATH correctly as, you can use **man cdist-reference** to access
the reference with pointers to the manpages.

PARTS BELOW HERE ARE TO-BE-DONE

-> ssh stuff double: cdist-best-practice and here


CONTINUE READING
----------------
So far you have seen how to get cdist up and running and
how the initial manifest is being used.

own branch => very early [before first change?]
    => no, first quick intro, then do it right
It is recommended to 
- MANAGING YOUR OWN CONFIGURATION
- write own type


MANAGING YOUR OWN CONFIGURATION
-------------------------------

CREATING YOUR FIRST OWN TYPE
----------------------------
=> short example, reference to cdist-type(7)!
=> motivation

Use a type to bundle functionalitY

<with object id? or signleton here already>

Debug with var - can be used by yourself
__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



USING EXPLORERS
---------------
cdist-explorer.text


DEBUGGING YOUR TYPES
--------------------



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

- speedup processing with ControlMaster option of
ssh
=> different document


SEE ALSO
--------
- cdist(1)
- cdist-type(7)
- cdist-best-practice(7)
- cdist-stages(7)?