States tutorial, part 2 - More Complex States, Requisites


This tutorial builds on topics covered in part 1. It is recommended that you begin there.

In the last part of the Salt States tutorial we covered the basics of installing a package. We will now modify our webserver.sls file to have requirements, and use even more Salt States.

Call multiple States

You can specify multiple State declaration under an ID declaration. For example, a quick modification to our webserver.sls to also start Apache if it is not running:

2  pkg.installed: []
3  service.running:
4    - require:
5      - pkg: apache

Try stopping Apache before running state.apply once again and observe the output.


For those running RedhatOS derivatives (Centos, AWS), you will want to specify the service name to be httpd. More on state service here, service state. With the example above, just add "- name: httpd" above the require line and with the same spacing.

Require other states

We now have a working installation of Apache so let's add an HTML file to customize our website. It isn't exactly useful to have a website without a webserver so we don't want Salt to install our HTML file until Apache is installed and running. Include the following at the bottom of your webserver/init.sls file:

 2  pkg.installed: []
 3  service.running:
 4    - require:
 5      - pkg: apache
 7/var/www/index.html:                        # ID declaration
 8  file:                                     # state declaration
 9    - managed                               # function
10    - source: salt://webserver/index.html   # function arg
11    - require:                              # requisite declaration
12      - pkg: apache                         # requisite reference

line 7 is the ID declaration. In this example it is the location we want to install our custom HTML file. (Note: the default location that Apache serves may differ from the above on your OS or distro. /srv/www could also be a likely place to look.)

Line 8 the State declaration. This example uses the Salt file state.

Line 9 is the Function declaration. The managed function will download a file from the master and install it in the location specified.

Line 10 is a Function arg declaration which, in this example, passes the source argument to the managed function.

Line 11 is a Requisite declaration.

Line 12 is a Requisite reference which refers to a state and an ID. In this example, it is referring to the ID declaration from our example in part 1. This declaration tells Salt not to install the HTML file until Apache is installed.

Next, create the index.html file and save it in the webserver directory:

<!DOCTYPE html>
    <head><title>Salt rocks</title></head>
        <h1>This file brought to you by Salt</h1>

Last, call state.apply again and the minion will fetch and execute the highstate as well as our HTML file from the master using Salt's File Server:

salt '*' state.apply

Verify that Apache is now serving your custom HTML.

require vs. watch

There are two Requisite declaration, “require”, and “watch”. Not every state supports “watch”. The service state does support “watch” and will restart a service based on the watch condition.

For example, if you use Salt to install an Apache virtual host configuration file and want to restart Apache whenever that file is changed you could modify our Apache example from earlier as follows:

    - source: salt://webserver/httpd-vhosts.conf

  pkg.installed: []
    - watch:
      - file: /etc/httpd/extra/httpd-vhosts.conf
    - require:
      - pkg: apache

If the pkg and service names differ on your OS or distro of choice you can specify each one separately using a Name declaration which explained in Part 3.

Next steps

In part 3 we will discuss how to use includes, extends, and templating to make a more complete State Tree configuration.