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?

There are many ways to get help from the Salt community including our mailing list and our IRC channel #salt.

Setting up the Salt State Tree

States are stored in text files on the master and transferred 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, the Salt File Server must first be set up. Edit the master config file (file_roots) and uncomment the following lines:

file_roots:
  base:
    - /srv/salt

Note

If you are deploying on FreeBSD via ports, the file_roots path defaults to /usr/local/etc/salt/states.

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 uncommented in the previous step, (/srv/salt by default), 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 the top file, create an empty file named webserver.sls, containing the following:

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 depending on 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. The default can be changed by editing 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.

SLS File Namespace

Note that in the example above, the SLS file webserver.sls was referred to simply as webserver. The namespace for SLS files follows a few simple rules:

  1. The .sls is discarded (i.e. webserver.sls becomes webserver).
  2. Subdirectories can be used for better organization.
    1. Each subdirectory is represented by a dot.
    2. webserver/dev.sls is referred to as webserver.dev.
  3. A file called init.sls in a subdirectory is referred to by the path of the directory. So, webserver/init.sls is referred to as webserver.
  4. If both webserver.sls and webserver/init.sls happen to exist, webserver/init.sls will be ignored and webserver.sls will be the file referred to as webserver.

Troubleshooting Salt

If the expected output isn't seen, the following tips can help to 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) one 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.