So how does this magical tool work? Well, let me break it down for you. First off, SaltStack is made up of two main components: a master server and minion clients. The master server acts as the brain of the operation, sending out commands to all its little minions (servers) and making sure they’re following orders.
Now, let’s say we want to make sure that every single one of our servers has the same version of Apache installed on them. We can write a recipe for this using SaltStack’s YAML syntax:
# This is an example recipe for installing Apache on all minion clients
# Added annotation to indicate the purpose of the script
apache_install: # Name of the recipe
pkg.installed: # Command to install a package
name: apache2 # Name of the package to be installed
state: present # State of the package, in this case, present means it should be installed
# Added annotation to explain the purpose of each code segment
This tells the master server to send out a command to every single one of its minions, telling them to install the package called “apache2” and make sure it’s present on their system. Pretty simple, right?
But what if we want to do something more complex than just installing packages? Let’s say we have a custom script that needs to be run on every single one of our servers at the same time. We can write another recipe for this using SaltStack’s Jinja templating language:
# This is an example recipe for running a custom script on all minion clients
custom_script:
file.managed:
name: /path/to/my/script.sh # Specifies the path and name of the script to be managed
source: salt://scripts/my-script.sh # Specifies the source of the script, in this case it is located in the "scripts" directory within the SaltStack file server
mode: '0755' # Sets the permissions of the script to be executable by all users
cmd.script:
- name: /path/to/my/script.sh # Specifies the path and name of the script to be executed
- shell: bash # Specifies the shell to be used for executing the script
- require:
- file: custom_script # Specifies that the file.managed state must be successfully executed before running the script
- watch:
- file: custom_script # Specifies that the script should be re-executed if any changes are made to the file.managed state
- onchanges:
- file: custom_script # Specifies that the script should be re-executed if any changes are made to the file.managed state
- onfail:
- file: custom_script # Specifies that the script should be re-executed if the file.managed state fails to execute
- onchanges_in:
- file: custom_script # Specifies that the script should be re-executed if any changes are made to the file.managed state, even if the state was previously successful
- onfail_in:
- file: custom_script # Specifies that the script should be re-executed if the file.managed state fails to execute, even if the state was previously successful
This tells the master server to send out a command to every single one of its minions, telling them to download our custom script from a remote location (in this case, using SaltStack’s built-in file management system), set it up with the correct permissions, and then run it using Bash. Pretty cool, huh?
SaltStack also has support for stateful configuration management, which means we can write recipes that define exactly how our servers should be configured at all times. For example:
# This is an example recipe for setting up a web server on all minion clients
web_server:
file.managed:
# Defines the name and location of the file to be managed
name: /etc/nginx/sites-available/my-site.conf
# Specifies the source of the file, in this case a file located in the Salt file management system
source: salt://configs/nginx/my-site.conf
# Sets the permissions for the file to be 0644, allowing read and write access for owner and read access for group and others
mode: '0644'
service.running:
# Defines the name of the service to be managed
name: nginx
# Specifies the desired state of the service, in this case to be started
state: started
This tells the master server to send out a command to every single one of its minions, telling them to download our web server configuration file from a remote location (in this case, using SaltStack’s built-in file management system), set it up with the correct permissions, and then start the nginx service. Pretty awesome, right?
That’s how SaltStack works in a nutshell. It’s like having your very own personal chef for configuration management, but instead of cooking up delicious meals, it’s making sure all your servers are running smoothly and following the same recipe (aka configuration). And with its support for stateful configuration management, you can be sure that every single one of your servers is configured exactly how you want them to be. Pretty cool stuff!