Getting Started with Salt Stack-the Other Configuration Management System Built with Python

Minion Configuration

For this tutorial, I cover issuing salt-master and salt-minion commands on the same machine. If you are configuring multiple machines, choose one to be the master, and all the others will be minions. The choice of master or minion is yours, and there are many reasons to configure one machine as the master. I explain how to set one as a master and the other(s) as minions next.

Salt's configuration files are located in /etc/salt. By default, these files are named minion and master. If you've installed the salt-master and salt-minion on the same machine, you will see two respective files, master and minion.

You first need to tell your minion how to locate and communicate with your master. Even though you are running both on the same server, you still need to tell your minion where your master is.

1. Using your favorite text editor, open the minion file.

2. Uncomment the line # master: salt by removing the # and replacing salt with the your master's IP address. It now should look like this: master: your.ip.address.here. (If you're doing this locally on the same machine, you can add 127.0.0.1.)

3. Give your minion a nickname. Locate the line #id:, and again remove the # and add a name id: 1st-Salt-Minion. (This name can be anything you want.)

4. Restart your minion using sudo salt-minion -d in order for it to read the new configuration settings. The -d flag dæmonizes the process and starts the minion in the background, so you still can access your command-line to issue more commands.

Accept Your Minion's Keys

Now that your minion knows where your master is, it's time for them to authenticate one another. Salt uses public key encryption to secure the communication between master and minions. You need to notify the master and minion that they can trust each other by accepting the minion's keys on the master.

Accept your minion's keys using the salt-key command. Salt automatically takes care of generating these keys for you, so you simply need to accept the minion(s) you want.

1. Type salt-key -L to get a list of all pending, accepted and rejected keys.

2. You should see an unaccepted key for 1st-Salt-Minion (or whatever ID you chose for your minion).

3. Accept this key using sudo salt-key -a 1st-Salt-Minion.

Test Communications

Now that you have a salt-master and a salt-minion, and the minion and master trust one another, you can check the connection by issuing a test ping command from the master. This will return "True" if your master can communicate with your minion. Type salt '*' test.ping, and it should return:

>{1st-Salt-Minion: True}

Note that the wild-card '*' targets every minion, and as you have only one, this is basically moot (it's just faster than typing salt '1st-Salt-Minion' test.ping).

If you receive a "True" response back from your minion, you have installed Salt Stack successfully and configured your master and minion to communicate properly.

If you don't, you may want to restart your master and minion without the -d (dæmon) flag, so you can observe the output. For more information, see the Salt documentation at http://docs.saltstack.org/en/latest/topics/configuration.html.

The Salt command syntax involves the command, the target(s) and the action. So, for this example, '*' targets everything (it's a wild card), and test.ping is the action.

You can now execute any available command on any connected and authenticated minion. Important note: these commands must be available on the targeted minion in order to execute them. For instance, a command like:

sudo salt '*' cmd.run "service apache2 restart"

would work only for a distribution that calls the Apache Web server apache2 and that has the Apache Web server installed. For others, you would need to issue the command:

sudo salt '*' cmd.run "service httpd restart"

Some other examples might include querying the amount of time your servers have been running. You can do that with:

sudo salt '*' cmd.run "uptime"

If you had, for example, Apache Bench installed on a master but not on a minion, the command:

sudo salt '*' cmd.run "ab -n 10 -c 2 http://www.google.com:80/index.html"

would fail if you tried to execute it on a minion, since Apache Bench isn't installed on the minion.

The possibilities here are practically limitless. You can reboot all of your machines at once, update system software and check your machines' health from one terminal instead of logging in to each machine and issuing these commands independently.

You also can target specific groups, based upon criteria that you select. See the -G flag documentation at http://saltstack.org for more options.

Very rarely should you ever need to log in to a minion again. All configuration and execution can be handled remotely, quickly and simultaneously.

Now that you've installed Salt and can execute remote commands, why stop there? The second part of Salt's power comes from the configuration management tools included with Salt.