While automation exists to make it easier to make things repeatable, all of your systems are likely not exactly alike. On some systems you may want to set some behavior or configuration that is slightly different from others. Also, some of the observed behavior or state of remote systems might need to influence how you configure those systems. Such as you might need to find out the IP address of a system and even use it as a configuration value on another system.
You might have some templates for configuration files that are mostly the same, but slightly different based on those variables. For best practices advice, refer to Variables and Vaults in the Best Practices chapter. Variable names should be letters, numbers, and underscores. Variables should always start with a letter.
You can then reference a specific field in the dictionary using either bracket notation or dot notation:.
However, if you choose to use dot notation be aware that some keys can cause problems because they collide with attributes and methods of python dictionaries. You should use bracket notation instead of dot notation if you use keys which start and end with two underscores Those are reserved for special meanings in python or are any of the known public attributes:.
See the Inventory document for multiple ways on how to define variables in inventory. Usage of roles is preferred as it provides a nice organizational system.
Ansible allows you to reference variables in your playbooks using the Jinja2 templating system. While you can do a lot of complex things in Jinja, only the basics are things you really need to learn at first. Inside a template you automatically have access to all of the variables that are in scope for a host. Ansible playbooks are pure machine-parseable YAML. This is a rather important feature as it means it is possible to code-generate pieces of files, or to have other ecosystem tools read Ansible files.
Not everyone will need this but it can unlock possibilities.
How to Work with Ansible Variables and Facts – Part 8
These are infrequently utilized features. Use them if they fit a use case you have, but this is optional knowledge. Filters in Jinja2 are a way of transforming template expressions from one kind of data into another. Jinja2 ships with many of these. See builtin filters in the official Jinja2 template documentation. In addition to those, Ansible supplies many more. See the Filters document for a list of available filters and example usage guide.A variablejust like in many programming languages, is essentially a key that represents a value.
A variable name includes letters, numbers, underscores or a mix of either 2 or all of them. However, bear in mind that a variable name must always begin with a letter and should not contain spaces.
Playbook variables are quite easy and straightforward. To define a variable in a playbooksimply use the keyword vars before writing your variables with indentation.
To access the value of the variable, place it between the double curly braces enclosed with quotation marks. In the above playbook, the greeting variable is substituted by the value Hello world! The playbook simply prints the message Hello world!
The playbook below shows a variable called continents. The variable holds 5 different values — continent names. Each of these values can easily be accessed using index 0 as the first variable. This will loop through all the values in the array. Dictionary variables are additionally supported in the playbook. To define the dictionary variable, simply ident the key-value pair just below the dictionary variable name.
In the example above, vlans is the dictionary variable while id and port are the key-value pairs. Ansible provides a list of predefined variables that can be referenced in Jinja2 templates and playbooks but cannot be altered or defined by the user.
Collectively, the list of Ansible predefined variables is referred to as Ansible facts and these are gathered when a playbook is executed.
To get a list of all the Ansible variables, use the setup module in the Ansible ad-hoc command as shown below:. Lastly, on the list, we have Ansible inventory variables. An inventory is a file in INI format that contains all the hosts to be managed by Ansible.
If the host systems share the same variables, you can define another group in the inventory file to make it less cumbersome and avoid unnecessary repetition. When running playbooks, the first task that Ansible does is the execution of setup task.
Ansible facts are nothing but system properties or pieces of information about remote nodes that you have connected to. This information includes the System architecture, the OS version, BIOS information, system time and date, system uptime, IP address, and hardware information to mention just a few. To get the facts about any system simply use the setup module as shown in the command below:. Ansible facts are handy in helping the system administrators which operations to carry out, for instance, depending on the operating system, they are able to know which software packages need to be installed, and how they are to be configured, etc.
Did you also know that you can create your own custom facts that can be gathered by Ansible? Yes, you can. So how do you go about it? Inside this directory, create a file s with a. This file s will return JSON data when the playbook is run on the Ansible control node, which is inclusive of the other facts that Ansible retrieves after a playbook run.This allows you to define a custom credential type that works in ways similar to existing credential types.
For example, you could create a custom credential type that injects an API token for a third-party web service into an environment variable, which your playbook or custom inventory script could consume. Each cloud credential must be of a different type. In Ansible Tower 3. You must have Superuser permissions to be able to create and edit a credential type CredentialType and to be able to view the CredentialType.
Starting in Ansible Tower version 3. Access the Credentials from clicking the Credential Types icon from the left navigation bar. If no custom credential types have been created, the Credential Types view will not have any to display and will prompt you to add one:. If credential types have been created, this page displays a list of all existing and available Credential Types. It can be sorted and searched by Name and Kind. To view more information about a credential type, click on its name or the Edit button from the Actions column.
Each credential type displays its own unique configurations in the Input Configuration field and the Injector Configuration field, if applicable. Credential Types can also generate temporary files to support.
Click to modify or to remove the credential type options under the Actions column. If deleting a credential type that is being used by a credential, you must delete the credential type from all the credentials that use it before you can delete it. Below is an example of such a message:. For details on how to create a new credential, see Credentials. Are you using the latest and greatest version of Ansible Tower?
Find the Ansible Tower documentation set which best matches your version of Tower. Ansible Tower User Guide v3. Overview 1. Real-time Playbook Output and Exploration 1. Backup and Restore 1. Ansible Galaxy Integration 1. Inventory Support for OpenStack 1. Remote Command Execution 1. System Tracking 1. Integrated Notifications 1. Satellite and CloudForms Integration 1. Run-time Job Customization 1.Variables are used to store values in programs and as the name suggests the values can be changed throughout the program.
These values are essential to deciding the code flow. Ansible variable names should be letters, numbers, underscores and they should always start with a letter. The task will output the value world. The following task shows how to declare an array variable in Ansible and how to use the values.
For more details n how to use the loop structure for this tutorial.
Ansible - Variables
You can declare dictionaries in Ansible as you would in a python script. And you can access any of the value using the key. In the following task, I am declaring a variable python which has 3 key-value pairs inside. The following task would print the whole dictionary structure. You can access the individual values in the dictionary variable using the key name.Ansible-playbook -- YAML Scripting - video - 9 - How to use command line variable in playbook ?
There are two ways for this, using the dot notation or the bracket notation. Both will print the name of the designer. The key and value will be available from item. It is possible to give variable values in multiple lines using YAML block operators.
Ansible Dictionary Variables Hash You can declare dictionaries in Ansible as you would in a python script. Ansible Variables Long. Using grep commands in Ansible tasks. Working with Ansible Register Variables.While automation exists to make it easier to make things repeatable, all systems are not exactly alike; some may require configuration that is slightly different from others.
In some instances, the observed behavior or state of one system might influence how you configure other systems. For example, you might need to find out the IP address of a system and use it as a configuration value on another system.
The ansible-examples github repository contains many examples of how variables are used in Ansible. Variable names should be letters, numbers, and underscores. Variables should always start with a letter. You can then reference a specific field in the dictionary using either bracket notation or dot notation:. However, if you choose to use dot notation be aware that some keys can cause problems because they collide with attributes and methods of python dictionaries.
You should use bracket notation instead of dot notation if you use keys which start and end with two underscores Those are reserved for special meanings in python or are any of the known public attributes:. The How to build your inventory page has details on setting Assigning a variable to one machine: host variables and Assigning a variable to many machines: group variables in inventory.
As described in Rolesvariables can also be included in the playbook via include files, which may or may not be part of an Ansible Role. Usage of roles is preferred as it provides a nice organizational system.
Inside a template you automatically have access to all variables that are in scope for a host. Ansible playbooks are pure machine-parseable YAML. This is a rather important feature as it means it is possible to code-generate pieces of files, or to have other ecosystem tools read Ansible files.
Not everyone will need this but it can unlock possibilities. Jinja2 filters let you transform the value of a variable within a template expression.
Jinja2 includes many built-in filters and Ansible supplies many more filters. There are other places where variables can come from, but these are a type of variable that are discovered, not set by the user.
Facts are information derived from speaking with your remote systems. Facts are frequently used in conditionals see Conditionals and also in templates. This has advantages in scaling Ansible in push mode with very large numbers of systems, mainly, or if you are using Ansible on experimental platforms. In any play, just do this:. As discussed in the playbooks chapter, Ansible facts are a way of getting data about remote systems for use in playbook variables. Usually these are discovered automatically by the setup module in Ansible.
Users can also write custom facts modules, as described in the API guide. However, what if you want to have a simple way to provide system or user provided data for use in Ansible variables, without writing a fact module?
This will produce a hash variable fact named general with asdf and bar as members. To validate this, run the following:. The local namespace prevents any user supplied fact from overriding system facts or variables defined elsewhere in the playbook. If you have a playbook that is copying over a custom fact and then running it, making an explicit call to re-run the setup module can allow that fact to be used during that particular play.
Otherwise, it will be available in the next play that gathers fact information. Here is an example of what that might look like:. In this pattern however, you could also write a fact module as well, and may wish to consider this as an option.
As shown elsewhere in the docs, it is possible for one server to reference variables about another, like so:. This is the default configuration of ansible. To avoid this, Ansible 1.Also covered, What does ansible Gathering facts tasks do in ansible playbook execution, data types of ansible variables and how to know the data type of ansible variable including how to access the ansible dictionary and list objects.
We are going to start from the ansible Gathering facts. As ansible collected facts are considered as the ansible playbook variables or facts. Ansible collects pretty much all the information about the remote hosts as it runs a playbook.
The task of collecting this remote system information is called as Gathering Facts by ansible and the details collected are generally known as facts or variables. Here is the list of facts would be returned when you run the ansible hostgroup -m setup command against any host group. Hope the preceding execution output gives you a clear picture on what information or facts are being collected as part of gathering facts.
You can use all of these variables in your playbook. These are only a few purposes listed where the variables are used, there are quite a lot of scenarios where the ansible built-in variables or collected facts come in handy.
Though you can use all these variables at your convenience. You should be aware how to access the variable as they are stored in JSON tree or array.
To use the variable in your playbook and succeed at it. All you have to keep in mind is the the type of variable you are trying to access. From the preceding execution output of setup moduleLet us do some categorization to find the different types of variables. I have taken the first few lines of execution output and marked the variables with their corresponding types in the following snap. Basically, the Ansible UnSafe Text is the statement which is an end variable or key python which holds the value.
It can either be part of Dictionary or stand alone. You can use these facts in your playbook for accomplishing your various requirements. Let us start with the basics. For better understanding and to be in Sync, I am going to refer to the image Snap 1. Having three variables for the three data types, Now let us go and write a playbook to access these different type of variables.
The following playbook is designed to display the data type of each variable and then print the value of them. As you could notice, to access the element of the.Variable in playbooks are very similar to using variables in any programming language. It helps you to use and assign a value to a variable and use that anywhere in the playbook.
One can put conditions around the value of the variables and accordingly use them in the playbook. Now taking a reference from the example shared. The action again is a Ansible keyword used in yaml. This will read the value of variable Output. Also as it is used in the msg tab, it will print the value of the output variable.
Additionally, you can use the sub properties of the variable as well. Exception handling in Ansible is similar to exception handling in any programming language. An example of the exception handling in playbook is shown below. If the command written inside the block feature fails, then the execution reaches rescue block and it gets executed.
In case there is no error in the command under block feature, then rescue will not be executed. Here, Block is similar to try block where you write the code to be executed and rescue is similar to catch block and always is similar to finally. Most of the commands used in the example below are already covered before. Here, we will concentrate on the usage of loops. So, it will list all the war files in the directory. The playbook in totality is broken into blocks.
The smallest piece of steps to execute is written in block. Writing the specific instruction in blocks helps to segregate functionality and handle it with exception handling if needed. In this case, Equals will be printed as the test1 variable is equal as mentioned in the when condition. Ansible - Variables Advertisements.
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