The 5 Cent Salt Intro¶

Since you're here you've probably already heard about Salt, so you already know Salt lets you configure and run commands on hordes of servers easily. Here's a brief overview of a Salt cluster:

• Salt works by having a "master" server sending commands to one or multiple "minion" servers [1]. The master server is the "command center". It is going to be the place where you store your configuration files, aka: "which server is the db, which is the web server, and what libraries and software they should have installed". The minions receive orders from the master. Minions are the servers actually performing work for your business.

• Salt has two types of configuration files:

  1. the "salt communication channels" or "meta" or "config" configuration files (not official names): one for the master (usually is /etc/salt/master , on the master server), and one for minions (default is /etc/salt/minion or /etc/salt/minion.conf, on the minion servers). Those files are used to determine things like the Salt Master IP, port, Salt folder locations, etc.. If these are configured incorrectly, your minions will probably be unable to receive orders from the master, or the master will not know which software a given minion should install.

  2. the "business" or "service" configuration files (once again, not an official name): these are configuration files, ending with ".sls" extension, that describe which software should run on which server, along with particular configuration properties for the software that is being installed. These files should be created in the /srv/salt folder by default, but their location can be changed using ... /etc/salt/master configuration file!

Before Digging In, The Architecture Of The Salt Cluster¶

Install Homebrew¶

Install Homebrew here http://brew.sh/ Or just type

ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"

Now type the following commands in your terminal (you may want to type brew doctor after each to make sure everything's fine):

brew install python
brew install swig
brew install zmq

Install Salt¶

You should now have everything ready to launch this command:

pip install salt

Now type python in a terminal then, import salt. There should be no errors. Now exit the Python terminal using exit().

Create The Master Configuration¶

If the default /etc/salt/master configuration file was not created, copy-paste it from here: http://docs.saltstack.com/ref/configuration/examples.html#configuration-examples-master

Salt Master configuration changes. The Salt master needs a few customization to be able to run on Mac OS X:

sudo launchctl limit maxfiles 4096 8192

In the /etc/salt/master file, change max_open_files to 8192 (or just add the line: max_open_files: 8192 (no quote) if it doesn't already exists).

You should now be able to launch the Salt master:

sudo salt-master --log-level=all

There should be no errors when running the above command.

Now that the master is set, let's configure a minion on a VM.

Install VirtualBox¶

Go get it here: https://www.virtualBox.org/wiki/Downloads (click on VirtualBox for OS X hosts => x86/amd64)

Install Vagrant¶

Go get it here: http://downloads.vagrantup.com/ and choose the latest version (1.3.5 at time of writing), then the .dmg file. Double-click to install it. Make sure the vagrant command is found when run in the terminal. Type vagrant. It should display a list of commands.

Create The Minion VM Folder¶

Create a folder in which you will store your minion's VM. In this tutorial, it's going to be a minion folder in the $home directory.

cd $home
mkdir minion

Initialize Vagrant¶

From the minion folder, type

vagrant init

This command creates a default Vagrantfile configuration file. This configuration file will be used to pass configuration parameters to the Salt provisioner in Step 3.

Import Precise64 Ubuntu Box¶

vagrant box add precise64 http://files.vagrantup.com/precise64.box

Modify the Vagrantfile¶

Modify ./minion/Vagrantfile to use th precise64 box. Change the config.vm.box line to:

config.vm.box = "precise64"

Uncomment the line creating a host-only IP. This is the ip of your minion (you can change it to something else if that IP is already in use):

config.vm.network :private_network, ip: "192.168.33.10"

At this point you should have a VM that can run, although there won't be much in it. Let's check that.

Checking The VM¶

From the $home/minion folder type:

vagrant up

A log showing the VM booting should be present. Once it's done you'll be back to the terminal:

ping 192.168.33.10

The VM should respond to your ping request.

Now log into the VM in ssh using Vagrant again:

vagrant ssh

You should see the shell prompt change to something similar to vagrant@precise64:~$ meaning you're inside the VM. From there, enter the following:

ping 10.0.2.2

It's now time to connect the VM to the salt master

Creating The Minion Configuration File¶

Create the /etc/salt/minion file. In that file, put the following lines, giving the ID for this minion, and the IP of the master:

master: 10.0.2.2
id: 'minion1'
file_client: remote

Minions authenticate with the master using keys. Keys are generated automatically if you don't provide one and can accept them later on. However, this requires accepting the minion key every time the minion is destroyed or created (which could be quite often). A better way is to create those keys in advance, feed them to the minion, and authorize them once.

Preseed minion keys¶

From the minion folder on your Mac run:

sudo salt-key --gen-keys=minion1

This should create two files: minion1.pem, and minion1.pub. Since those files have been created using sudo, but will be used by vagrant, you need to change ownership:

sudo chown youruser:yourgroup minion1.pem
sudo chown youruser:yourgroup minion1.pub

Then copy the .pub file into the list of accepted minions:

sudo cp minion1.pub /etc/salt/pki/master/minions/minion1

Modify Vagrantfile to Use Salt Provisioner¶

Let's now modify the Vagrantfile used to provision the Salt VM. Add the following section in the Vagrantfile (note: it should be at the same indentation level as the other properties):

# salt-vagrant config
config.vm.provision :salt do |salt|
    salt.run_highstate = true
    salt.minion_config = "/etc/salt/minion"
    salt.minion_key = "./minion1.pem"
    salt.minion_pub = "./minion1.pub"
end

Now destroy the vm and recreate it from the /minion folder:

vagrant destroy
vagrant up

If everything is fine you should see the following message:

"Bootstrapping Salt... (this may take a while)
Salt successfully configured and installed!"

Checking Master-Minion Communication¶

To make sure the master and minion are talking to each other, enter the following:

sudo salt '*' test.ping

You should see your minion answering the ping. It's now time to do some configuration.

Checking the system's original state¶

First, make sure that an HTTP server is not installed on our minion. When opening a browser directed at http://192.168.33.10/ You should get an error saying the site cannot be reached.

Initialize the top.sls file¶

System configuration is done in /srv/salt/top.sls (and subfiles/folders), and then applied by running the state.apply function to have the Salt master order its minions to update their instructions and run the associated commands.

First Create an empty file on your Salt master (Mac OS X machine):

touch /srv/salt/top.sls

When the file is empty, or if no configuration is found for our minion an error is reported:

sudo salt 'minion1' state.apply

This should return an error stating: No Top file or external nodes data matches found.

Create The Nginx Configuration¶

Now is finally the time to enter the real meat of our server's configuration. For this tutorial our minion will be treated as a web server that needs to have Nginx installed.

Insert the following lines into /srv/salt/top.sls (which should current be empty).

base:
  'minion1':
    - bin.nginx

Now create /srv/salt/bin/nginx.sls containing the following:

nginx:
  pkg.installed:
    - name: nginx
  service.running:
    - enable: True
    - reload: True

Check Minion State¶

Finally, run the state.apply function again:

sudo salt 'minion1' state.apply

You should see a log showing that the Nginx package has been installed and the service configured. To prove it, open your browser and navigate to http://192.168.33.10/, you should see the standard Nginx welcome page.

Congratulations!

Where To Go From Here¶

A full description of configuration management within Salt (sls files among other things) is available here: http://docs.saltstack.com/en/latest/index.html#configuration-management