Writing your first salt module

Salt modules are simply python files that are executed by the running minion on the minion-server, after being told to by the salt-master. Some environment and configuration can be passed in, but most of what we need is available by introspecting the minion-host.

Where to put a salt module?

First create {FILES_ROOT}/_modules/. FILES_ROOT is defined in /etc/salt/master, and defaults to /srv/salt

Now create a python module in the _modules directory, such as pbrian.py

Simplest possible salt module:

import salt

def hello()
    return "hello world"

And that’s it.

Synchronise from the salt-master to the minion(s)

salt '*' saltutils.sync_all
     ^
     selects which minions

 $ sudo salt 'myinstance' saltutil.sync_all
 myinstance:
     ----------
     grains:
     modules:
         - modules.pbrian
     outputters:
     renderers:
     returners:
     states:

This will synch the _modules directory (and lots else) from master to minion. So modules are either those you have written and deployed into _modules yourself, or are properly incorporated into the main salt repos

Now run your module on the minion

$ sudo salt 'myinstance' pbrian.hello
myinstance:
    hello world

Hooray!

So lets recap.

We can manually build a salt-master. We can then auto build any number of minions (up to our credit card limit !) Then we can write a python module to do anything on the minion, deploy it and get its output returned to us.

Next steps

• Better Python Integration.
• Actually building our build server.