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

NAME
----
cdist-best-practice - Practices used in real environments


PASSWORDLESS CONNECTIONS
------------------------
It is recommended to run cdist with public key authentication.
This requires a private/public key pair and the entry
"PermitRootLogin without-password" in the sshd server.
See sshd_config(5) and ssh-keygen(1).


SPEEDING UP SSH CONNECTIONS
---------------------------
When connecting to a new host, the initial delay with ssh connections
is pretty big. You can work around this by
"sharing of multiple sessions over a single network connection"
(quote from ssh_config(5)). The following code is suitable for
inclusion into your ~/.ssh/config:

--------------------------------------------------------------------------------
Host *
  ControlPath ~/.ssh/master-%l-%r@%h:%p
  ControlMaster auto
  ControlPersist 10
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SPEEDING UP SHELL EXECUTION
----------------------------
On the source host, ensure that /bin/sh is *not* bash: bash is quite slow for
script execution. Instead, you could use dash after installing it:

--------------------------------------------------------------------------------
ln -sf /bin/dash /bin/sh
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MULTI MASTER OR ENVIRONMENT SETUPS
----------------------------------
If you plan to distribute cdist among servers or use different
environments, you can do so easily with the included version
control git. For instance if you plan to use the typical three
environments production, integration and development, you can
realise this with git branches:

--------------------------------------------------------------------------------
# Go to cdist checkout
cd /path/to/cdist

# Create branches
git branch development
git branch integration
git branch production

# Make use of a branch, for instance production
git checkout production
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Similar if you want to have cdist checked out at multiple machines,
you can clone it multiple times:

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machine-a % git clone git://your-git-server/cdist
machine-b % git clone git://your-git-server/cdist
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SEPERATING WORK BY GROUPS
-------------------------
If you are working with different groups on one cdist-configuration,
you can delegate to other manifests and have the groups edit only
their manifests. You can use the following snippet in
**conf/manifests/init**:

--------------------------------------------------------------------------------
# Include other groups
sh -e "$__manifest/systems"

sh -e "$__manifest/cbrg"
--------------------------------------------------------------------------------


MAINTAINING MULTIPLE CONFIGURATIONS
-----------------------------------
When you need to manage multiple sites with cdist, like company_a, company_b
and private for instance, you can easily use git for this purpose.
Including a possible common base that is reused accross the different sites:

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# create branches
git branch company_a company_b common private

# make stuff for company a
git checkout company_a
# work, commit, etc.

# make stuff for company b
git checkout company_b
# work, commit, etc.

# make stuff relevant for all sites
git checkout common
# work, commit, etc.

# change to private and include latest common stuff
git checkout private
git merge common
--------------------------------------------------------------------------------

The following **.git/config** is taken from a a real world scenario:
--------------------------------------------------------------------------------
# Track upstream, merge from time to time
[remote "upstream"]
   url = git://git.schottelius.org/cdist
   fetch = +refs/heads/*:refs/remotes/upstream/*

# Same as upstream, but works when being offline 
[remote "local"]
   fetch = +refs/heads/*:refs/remotes/local/*
   url = /home/users/nico/p/cdist

# Remote containing various ETH internal branches
[remote "eth"]
   url = sans.ethz.ch:/home/services/sans/git/cdist-eth
   fetch = +refs/heads/*:refs/remotes/eth/*

# Public remote that contains my private changes to cdist upstream
[remote "nico"]
   url = git.schottelius.org:/home/services/git/cdist-nico
   fetch = +refs/heads/*:refs/remotes/nico/*

# The "nico" branch will be synced with the remote nico, branch master
[branch "nico"]
   remote = nico
   merge = refs/heads/master

# ETH stable contains rock solid configurations used in various places
[branch "eth-stable"]
   remote = eth
   merge = refs/heads/stable
--------------------------------------------------------------------------------

Have a look at git-remote(1) to adjust the remote configuration, which allows


MULTIPLE DEVELOPERS WITH DIFFERENT TRUST
----------------------------------------
If you are working in an environment that requires different people to
work on the same configuration, but having different privileges, you can
implement this scenario with a gateway host and sudo:

- Create a dedicated user (for instance **cdist**)
- Setup the ssh-pubkey for this user that has the right to configure all hosts
- Create a wrapper to update the cdist configuration in ~cdist/cdist
- Allow every developer to execute this script via sudo as the user cdist
- Allow run of cdist as user cdist on specific hosts on a per user/group base
    - f.i. nico ALL=(ALL) NOPASSWD: /home/cdist/bin/cdist config hostabc

For more details consult sudoers(5)

TEMPLATING
----------
* create directory templates/ in your type (convention)
* create the template as an executable file like templates/basic.conf.sh, it will output text using shell variables for the values

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#!/bin/sh
# in the template, use cat << eof (here document) to output the text
# and use standard shell variables in the template
# output everything in the template script to stdout
cat << EOF
server {
  listen                          80;
  server_name                     $SERVERNAME;
  root                            $ROOT;

  access_log /var/log/nginx/$SERVERNAME_access.log
  error_log /var/log/nginx/$SERVERNAME_error.log
}
EOF
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* in the manifest, export the relevant variables and add the following lines in your manifest:
--------------------------------------------------------------------------------------
# export variables needed for the template
  export SERVERNAME='test"
  export ROOT='/var/www/test'
# render the template
  mkdir -p "$__object/files"
  "$__type/templates/basic.conf.sh" > "$__object/files/basic.conf"
# send the rendered template 
  __file /etc/nginx/sites-available/test.conf  --state present   --source "$__object/files/basic.conf"
--------------------------------------------------------------------------------------

SEE ALSO
--------
- cdist(1)
- 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).
