States tutorial, part 1

The purpose of this tutorial is to demonstrate how quickly you can configure a system to be managed by Salt States. For detailed information about the state system please refer to the full states reference.

This tutorial will walk you through using Salt to configure a minion to run the Apache HTTP server and to ensure the server is running.

Before continuing make sure you have a working Salt installation by following the installation and the configuration instructions.

Stuck?

If you get stuck at any point, there are many ways to get help from the Salt community including our mailing list and our IRC channel.

Setting up the Salt State Tree

States are stored in text files on the master and transfered to the minions on demand via the master's File Server. The collection of state files make up the State Tree.

To start using a central state system in Salt you must first set up the Salt File Server. Edit your master config file (file_roots) and uncomment the following lines:

file_roots:
  base:
    - /srv/salt

Restart the Salt master in order to pick up this change:

% pkill salt-master
% salt-master -d

Preparing the Top File

On the master in the directory you specified in the previous step, create a new file called top.sls and add the following:

base:
  '*':
    - webserver

The top file is separated into environments (discussed later). The default environment is base. Under the base environment a collection of minion matches is defined; for now simply specify all hosts (*).

Targeting minions

The expressions can use any of the targeting mechanisms used by Salt — minions can be matched by glob, pcre regular expression, or by grains. For example:

base:
  'os:Fedora':
    - match: grain
    - webserver

Create an sls module

In the same directory as your top file, create an empty file, called an sls module, named webserver.sls. Type the following and save the file:

apache:                 # ID declaration
  pkg:                  # state declaration
    - installed         # function declaration

The first line, called the ID declaration, is an arbitrary identifier. In this case it defines the name of the package to be installed. NOTE: the package name for the Apache httpd web server may differ on your OS or distro — for example, on Fedora it is httpd but on Debian/Ubuntu it is apache2.

The second line, called the state declaration, defines which of the Salt States we are using. In this example, we are using the pkg state to ensure that a given package is installed.

The third line, called the function declaration defines which function in the pkg state module to call.

Renderers

States sls files can be written in many formats. Salt requires only a simple data structure and is not concerned with how that data structure is built. Templating languages and DSLs are a dime-a-dozen and everyone has a favorite.

Building the expected data structure is the job of Salt renderers and they are dead-simple to write.

In this tutorial we will be using YAML in Jinja2 templates which is the default format. You can change the default by changing renderer in the master configuration file.

Install the package

Next, let's run the state we created. Open a terminal on the master and run:

% salt '*' state.highstate

Our master is instructing all targeted minions to run state.highstate. When a minion executes a highstate call it will download the top file and attempt to match the expressions. When it does match an expression the modules listed for it will be downloaded, compiled, and executed.

Once completed, the minion will report back with a summary of all actions taken and all changes made.

Troubleshooting Salt

In case you don't see the expected output, the following tips can help you narrow down the problem.

Turn up logging

Salt can be quite chatty when you change the logging setting to debug:

salt-minion -l debug

Run the minion in the foreground

By not starting the minion in daemon mode (-d) you can view any output from the minion as it works:

salt-minion &

Increase the default timeout value when running salt. For example, to change the default timeout to 60 seconds:

salt -t 60

For best results, combine all three:

salt-minion -l debug &          # On the minion
salt '*' state.highstate -t 60  # On the master

Next steps

This tutorial focused on getting a simple Salt States configuration working. Part 2 will build on this example to cover more advanced sls syntax and will explore more of the states that ship with Salt.