Note
This tutorial builds on the topic 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.
You can specify multiple state declarations under an ID declaration. For example, a quick modification to our webserver.sls to also start Apache if it is not running:
1 2 3 4 5 6 7 | apache:
pkg:
- installed
service:
- running
- require:
- pkg: apache
|
Try stopping Apache before running state.highstate once again and observe the output.
As you have seen, SLS modules are appended with the file extension .sls and are referenced by name starting at the root of the state tree. An SLS module can be also defined as a directory. Demonstrate that now by creating a directory named webserver and moving and renaming webserver.sls to webserver/init.sls. Your state directory should now resemble:
|- top.sls
`- webserver/
`- init.sls
Organizing SLS modules
You can place additional .sls files in a state file directory. This affords much cleaner organization of your state tree on the filesystem. For example, if we created a webserver/django.sls file that module would be referenced as webserver.django.
In addition, States provide powerful includes and extending functionality which we will cover in Part 3.
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:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | apache:
pkg:
- installed
service:
- running
- require:
- pkg: apache
/var/www/index.html: # ID declaration
file: # state declaration
- managed # function
- source: salt://webserver/index.html # function arg
- require: # requisite declaration
- 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:
<html>
<head><title>Salt rocks</title></head>
<body>
<h1>This file brought to you by Salt</h1>
</body>
</html>
Last, call state.highstate 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.highstate
Verify that Apache is now serving your custom HTML.
require vs. watch
There are two requisite declarations, “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:
/etc/httpd/extra/httpd-vhosts.conf:
file:
- managed
- source: salt://webserver/httpd-vhosts.conf
apache:
pkg:
- installed
service:
- running
- 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.