Welcome to Salt Stack! I am excited that you are interested in Salt and starting down the path to better infrastructure management. I developed (and am continuing to develop) Salt with the goal of making the best software available to manage computers of almost any kind. I hope you enjoy working with Salt and that the software can solve your real world needs!
Note
This is the first of a series of walkthroughs and serves as the best entry point for people new to Salt, after this be sure to read up on pillar and more on states:
Salt is a different approach to infrastructure management, it is founded on the idea that high speed communication with large numbers of systems can open up new capabilities. This approach makes Salt a powerful multitasking system that can solve many specific problems in an infrastructure. The backbone of Salt is the remote execution engine, which creates a high speed, secure and bi-directional communication net for groups of systems. On top of this communication system Salt provides an extremely fast, flexible and easy to use configuration management system called Salt States.
This unique approach to management makes for a transparent control system that is not only amazingly easy to set up and use, but also capable of solving very complex problems in infrastructures; as will be explored in this walk through.
Salt is being used today by some of the largest infrastructures in the world and has a proven ability to scale to astounding proportions without modification. With the proven ability to scale out well beyond many tens of thousands of servers, Salt has also proven to be an excellent choice for small deployments as well, lowering compute and management overhead for infrastructures as small as just a few systems.
Salt Stack has been made to be very easy to install and get started. Setting up Salt should be as easy as installing Salt via distribution packages on Linux or via the Windows installer. The installation documents cover specific platform installation in depth:
Salt functions on a master/minion topology. A master server acts as a central control bus for the clients (called minions), and the minions connect back to the master.
Turning on the Salt Master is easy, just turn it on! The default configuration is suitable for the vast majority of installations. The Salt master can be controlled by the local Linux/Unix service manager:
On Systemd based platforms (OpenSuse, Fedora):
# systemctl start salt-master
On Upstart based systems (Ubuntu, older Fedora/RHEL):
# service salt-master start
On SysV Init systems (Debian, Gentoo etc.):
# /etc/init.d/salt-master start
Or the master can be started directly on the command line:
# salt-master -d
The Salt Master can also be started in the foreground in debug mode, thus greatly increasing the command output:
# salt-master -l debug
The Salt Master needs to bind to 2 TCP network ports on the system, these ports are 4505 and 4506. For more in depth information on fire walling these ports the firewall tutorial is available:
Note
The Salt Minion can operate with or without a Salt Master. This walkthrough assumes that the minion will be connected to the master, for information on how to run a master-less minion please see the masterless quickstart guide:
The Salt Minion only needs to be aware of one piece of information to run, the network location of the master. By default the minion will look for the DNS name salt for the master, making the easiest approach to set internal DNS to resolve the name salt back to the Salt Master IP. Otherwise the minion configuration file will need to be edited, edit the configuration option master to point to the DNS name or the IP of the Salt Master:
Note
The default location of the configuration files is /etc/salt, most platforms adhere to this convention, but platforms such as FreeBSD and Microsoft Windows place this file in different locations.
/etc/salt/minion:
master: saltmaster.example.com
Now that the master can be found, start the minion in the same way as the master; with the platform init system, or via the command line directly:
As a daemon:
# salt-minion -d
In the foreground in debug mode:
# salt-minion -l debug
Now that the minion is started it will generate cryptographic keys and attempt to connect to the master. The next step is to venture back to the master server and accept the new minion's public key.
Salt authenticates minions using public key encryption and authentication. For a minion to start accepting commands from the master the minion keys need to be accepted. The salt-key command is used to manage all of the keys on the master. To list the keys that are on the master run a salt-key list command:
# salt-key -L
The keys that have been rejected, accepted and pending acceptance are listed. The easiest way to accept the minion key is to accept all pending keys:
# salt-key -A
Note
Keys should be verified!! The secure thing to do is to run salt-key -P to verify that the keys on the master match the generated keys on the minions.
Now that the minion is connected to the master and authenticated, the master can start to command the minion. Salt commands allow for a vast set of functions to be executed and for specific minions and groups of minions to be targeted for execution. This makes the salt command very powerful, but the command is also very usable, and easy to understand.
The salt command is comprised of command options, target specification, the function to execute, and arguments to the function. A simple command to start with looks like this:
# salt '*' test.ping
The * is the target, which specifies all minions, and test.ping tells the minion to run the test.ping function. This salt command will tell all of the minions to execute the test.ping in parallel and return the result.
Note
All of the minions register themselves with a unique minion id, these ids default to the minion hostname, but can be explicitly defined in the minion config as well.
Salt comes with a vast library of functions available for execution, and Salt functions are self documenting. To see what functions are available on the minions execute the sys.doc function:
# salt '*' sys.doc
This will display a very large list of available functions and documentation on them, this documentation is also available online:
These functions cover everything from shelling out to package management to manipulating database servers. These functions comprise a powerful system management API which is the backbone to Salt configuration management and many other aspects of Salt.
Note
Salt comes with many plugin systems, the functions that are available via the salt command are called Execution Modules.
Some functions to be familiar with are around basic system management. Functions to shell out on minions such as cmd.run and cmd.run_all:
# salt '*' cmd.run 'ls -l /etc'
The pkg functions will automatically map local system package managers to the same salt functions. This means that pkg.install will wrap to installing packages via yum on Red Hat based systems and apt on Debian systems etc.
# salt '*' pkg.install vim
Salt uses a system called Grains to build up static data about minions. This data includes information about the operating system that is running, CPU architecture and much more. The grains system is used throughout Salt to deliver platform data to many components and to users.
Grains can also be statically set, this makes it easy to assign values to minions for grouping and managing. A common practice is to assign grains to minions to specify what the role or roles a minion might be. These static grains can be set in the minion configuration file or via the grains.set function.
Salt allows for minions to be targeted based on a wide range of criteria. The default targeting system uses globular expressions to match minions, hence if there are minions named larry1, larry2, curly1 and curly2, a glob of larry* will match larry1 and larry2, and a glob of *1 will match larry1 and curly1.
Many other targeting systems can be used other than globs, these systems include:
The concepts of targets are used on the command line with salt, but also function in many other areas as well, including the state system and the systems used for ACLs and user permissions.
Now that the basics are covered the time has come to evaluate States. Salt States, or the State System is the component of Salt made for configuration management. The State system is a fully functional configuration management system which has been designed to be exceptionally powerful while still being simple to use, fast, lightweight, deterministic and with salty levels of flexibility.
The state system is already available with a basic salt setup, no additional configuration is required, states can be set up immediately.
Note
Before diving into the state system, a brief overview of how states are constructed will make many of the concepts clearer. Salt states are based on data modeling, and build on a low level data structure that is used to execute each state function. Then more logical layers are built on top of each other. The high layers of the state system which this tutorial will cover consists of everything that needs to be known to use states, the two high layers covered here are the sls layer and the highest layer highstate.
Again, knowing that there are many layers of data management, will help with understanding states, but they never need to be used. Just as understanding how a compiler functions when learning a programming language, understanding what is going on under the hood of a configuration management system will also prove to be a valuable asset.
The state system is built on sls formulas, these formulas are built out in files on Salt's file server. To make a very basic sls formula open up a file under /srv/salt named vim.sls and get vim installed:
/srv/salt/vim.sls
vim:
pkg.installed
Now install vim on the minions by calling the sls directly:
# salt '*' state.sls vim
This command will invoke the state system and run the named sls which was just created "vim".
Now to beef up the vim sls formula a vimrc can be added:
/srv/salt/vim.sls
vim:
pkg.installed
/etc/vimrc:
file.managed:
- source: salt://vimrc
- mode: 644
- user: root
- group: root
Now the desired vimrc needs to be copied into the Salt file server to /srv/salt/vimrc, in Salt everything is a file, so no path redirection needs to be accounted for. The vimrc file is placed right next to the vim.sls file. The same command as above can be executed to all the vim sls formulas and now include managing the file.
Note
Salt does not need to be restarted/reloaded or have the master manipulated in any way when changing sls formulas, they are instantly available.
Obviously maintaining sls formulas right in the root of the file server will not scale out to reasonably sized deployments. This is why more depth is required. Start by making an nginx formula a better way, make an nginx subdirectory and add an init.sls file:
/srv/salt/nginx/init.sls
nginx:
pkg:
- installed
service:
- running
- require:
- pkg: nginx
A few things are introduced in this sls formula, first is the service statement which ensures that the nginx service is running, but the nginx service can't be started unless the package is installed, hence the require. The require statement makes sure that the required component is executed before and that it results in success.
Note
The require option belongs to a family of options called requisites. Requisites are a powerful component of Salt States, for more information on how requisites work and what is available see: Requisites Also evaluation ordering is available in Salt as well: Ordering States
Now this new sls formula has a special name, init.sls, when an sls formula is named init.sls it inherits the name of the directory path that contains it, so this formula can be referenced via the following command:
# salt '*' state.sls nginx
Now that subdirectories can be used the vim.sls formula can be cleaned up, but to make things more flexible (and to illustrate another point of course), move the vim.sls and vimrc into a new subdirectory called edit and change the vim.sls file to reflect the change:
/srv/salt/edit/vim.sls
vim:
pkg.installed
/etc/vimrc:
file.managed:
- source: salt://edit/vimrc
- mode: 644
- user: root
- group: root
The only change in the file is fixing the source path for the vimrc file. Now the formula is referenced as edit.vim because it resides in the edit subdirectory. Now the edit subdirectory can contain formulas for emacs, nano, joe or any other editor that may need to be deployed.
Two walkthroughs are specifically recommended at this point, first a deeper run through states:
Next an understanding of pillar is critical to using States:
Two more in depth states tutorials exist which move much more deeply into states functionality, Thomas' original states tutorial covers much more to get off the ground with States:
The States Tutorial also provides a fantastic introduction to states:
These tutorials include much more in depth information including templating sls formulas etc.
This concludes the initial Salt walkthrough, but there are many more things to learn still! These documents will cover important core aspects of Salt:
A few more tutorials are also available:
This still is only scratching the surface, many components such as the reactor and event systems, extending Salt, modular components and more are not covered here. For an overview of all Salt features and documentation look at the table of contents: