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.



QUICK START
-----------
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
--------------------------------------------------------------------------------


Before you can start using cdist, you need to ensure that
you can login 
sshd config!





You can copy and paste the following
code into your shell to get started and even configure your system.

--------------------------------------------------------------------------------
# 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
chmod 0700 conf/manifest/init

echo  'Ensure that you can login as root to localhost without password'
echo '(i.e. via public key) and then press return'
read tmp

# Configure localhost
./bin/cdist config localhost

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

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 (\_\_).



Everything you specify in manifests


# Intro of quickstart
#
cat << eof
$banner cdist version $__cdist_version

Welcome to the interactive guide to cdist!
This is the interactive tutorial and beginners help for cdist and here's
our schedule:

   - Stages:   How cdist operates
   - Explorer: Explore facts of the target host
   - Manifest: Map configurations to hosts
   - Types:    Bundled functionality
   - Deploy a configuration to the local host!

eof
__prompt "$continue"

################################################################################
# Stages
#
cat << eof

To deploy configurations to a host, you call

   cdist-deploy-to <hostname>

which makes calls to other scripts, which realise the so called "stages".
Usually you'll not notice this, but in case you want to debug or hack cdist,
you can run each stage on its own. Besides that, you just need to remember
that the command cdist-deploy-to is the main cdist command.

See also:

   Source of cdist-deploy-to(1), cdist-stages(7)

eof
__prompt "$continue"

################################################################################
# Explorer
#
cat << eof

The first thing cdist always does is running different explorers on the
target host. The explorers can be found in the directory

   ${__cdist_explorer_dir}

An explorer is executed on the target host and its output is saved to a file.
You can use these files later to decide what or how to configure the host.

For a demonstration, we'll call the OS explorer locally now, but remember:
This is only for demonstration, normally it is run on the target host.
The os explorer will which either displays the detected operating system or
nothing if it does not know your OS.

See also:

   cdist-explorer(7)

eof
explorer="${__cdist_explorer_dir}/os"

__prompt "Press enter to execute $explorer"

set -x
"$explorer"
set +x

################################################################################
# Manifest
#
cat << eof

The initial manifest is the entry point for cdist to find out, what you would
like to have configured. It is located at

   ${__cdist_manifest_init}

And can be as simple as

--------------------------------------------------------------------------------
__file /etc/cdist-configured --type file
--------------------------------------------------------------------------------

See also:

   cdist-manifest(7)

eof
__prompt "$continue"

cat << eof

Let's take a deeper look at the initial manifest to understand what it means:

   __file /etc/cdist-configured --type file
      |     |                    |        \\
      |     |        The parameter type    \\ With the value file
      |     |
      |     |
      |     | This is the object id
      |
   __file is a so called "type"


This essentially looks like a standard command executed in the shell.
eof
__prompt "$continue"

cat << eof

And that's exactly true. Manifests are shell snippets that can use
types as commands with arguments. cdist prepends a special path
that contain links to the cdist-type-emulator, to \$PATH, so you
can use your types as a command.

This is also the reason why types should always be prefixed with
"__", to prevent collisions with existing binaries.

The object id is unique per type and used to prevent you from creating
the same object twice.

Parameters are type specific and are always specified as --parameter <value>.

See also:

   cdist-type-build-emulation(1), cdist-type-emulator(1)

eof
__prompt "$continue"

################################################################################
# Types
#
cat << eof

Types are bundled functionality and are the main component of cdist.
If you want to have a feature x, you write the type __x. Types are stored in

   ${__cdist_type_dir}

And cdist ships with some types already!

See also:

   cdist-type(7)

eof
__prompt "Press enter to see available types"

set -x
ls ${__cdist_type_dir}
set +x

cat << eof

Types consist of the following parts:

   - ${__cdist_name_parameter} (${__cdist_name_parameter_required}/${__cdist_name_parameter_optional}
   - ${__cdist_name_manifest}
   - ${__cdist_name_explorer}
   - ${__cdist_name_gencode}

eof
__prompt "$continue"


cat << eof

Every type must have a directory named ${__cdist_name_parameter}, which
contains required or optional parameters (in newline seperated files).

If an object of a specific type was created in the initial manifest,
the manifest of the type is run and may create other objects.

A type may have ${__cdist_name_explorer}, which are very similar to the
${__cdist_name_explorer} seen above, but with a different purpose:
They are specific to the type and are not relevant for other types.

You may use them for instance to find out details on the target host,
so you can decide what to do on the target host eventually.

After the ${__cdist_name_manifest} and the ${__cdist_name_explorer} of
a type have been run, ${__cdist_name_gencode} is executed, which creates
code to be executed on the target on stdout.

eof
__prompt "$continue"

################################################################################
# Deployment
#

cat << eof

Now you've got some basic knowledge about cdist, let's configure your a host!

Ensure that you have a ssh server running on the host and that you can login as root.

eof

__prompt "Enter hostname or press enter for localhost: "

if [ "$answer" ]; then
   host="$answer"
else
   host="localhost"
fi

manifestinit="conf/manifest/init"
cat << eof

I'll now setup $manifestinit, containing the following code:

--------------------------------------------------------------------------------
# Every machine becomes a marker, so sysadmins know that automatic
# configurations are happening
__file /etc/cdist-configured

case "\$__target_host" in
   $host)
      __link /tmp/cdist-testfile --source /etc/cdist-configured  --type symbolic
      __addifnosuchline /tmp/cdist-welcome --line "Welcome to cdist"
   ;;
esac
--------------------------------------------------------------------------------

WARNING: This will overwrite ${manifestinit}.

eof

cat > "$__cdist_abs_mydir/../$manifestinit" << eof

# Every machine becomes a marker, so sysadmins know that automatic
# configurations are happening
__file /etc/cdist-configured

case "\$__target_host" in
   $host)
      __link /tmp/cdist-testfile --source /etc/cdist-configured  --type symbolic
      __addifnosuchline /tmp/cdist-welcome --line "Welcome to cdist"
   ;;
esac

eof

chmod u+x "$__cdist_abs_mydir/../$manifestinit"

cmd="cdist-deploy-to $host"

__prompt "Press enter to run \"$cmd\""

# No quotes, we need field splitting
$cmd

################################################################################
# End
#

cat << eof


--------------------------------------------------------------------------------
That's it, this is the end of the cdist-quickstart.

I hope you've got some impression on how cdist works, here are again some
pointers on where to continue to read:


eof

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