How to build your inventory, The default location for inventory is a file called /etc/ansible/hosts . Start with, you may add variables directly to the hosts and groups in your main inventory file. Ansible works against multiple managed nodes or "hosts" in your infrastructure at the same time, using a list or group of lists known as inventory. Once your inventory is defined, you use patterns to select the hosts or groups you want Ansible to run against.
The default location for inventory is a file called /etc/ansible/hosts. In this section I will be using the default inventory file i.e. /etc/ansible/hosts where I have added the hostnames of my managed nodes. Since we are using default inventory file so I won't specify the location of the inventory file in the ansible ad hoc commands examples. You can learn more about inventory when we reach Ansible Inventory chapter where we will learn about static and dynamic inventory files.
In Ansible, Playbook files are usually used in executing tasks in remote hosts. These tasks range from installing and configuring services such as web and database servers to simple tasks such as checking uptime. However, when it comes to executing simple tasks in Ansible, ad hoc commands come very much in handy. Ad hoc commands enable you to quickly execute simple tasks on the fly without writing playbook files. In this guide, we show you how you can make the most of Ansible ad hoc commands. When logged in as a regular user, you may be required to perform certain tasks on managed nodes that require elevated privileges or root privileges.
These tasks include package management, adding new users & groups, and modifying system configurations to mention just but a few. To achieve this, you need to invoke certain directives in the playbook to run the tasks as a privileged user on the remote hosts. When you execute Ansible through an ad hoc command or by running a playbook, you must choose which managed nodes or groups you want to execute against. Patterns let you run commands and playbooks against specific hosts and/or groups in your inventory. An Ansible pattern can refer to a single host, an IP address, an inventory group, a set of groups, or all hosts in your inventory. Patterns are highly flexible - you can exclude or require subsets of hosts, use wildcards or regular expressions, and more.
Ansible executes on all inventory hosts included in the pattern. For situations where commands require shell processing, administrators can use the shell module. Like the command module, you pass the commands to be executed as arguments to the module in an ad hoc command. Ansible then executes the command remotely on the managed hosts. Unlike the command module, the commands are processed through a shell on the managed hosts.
Therefore, shell environment variables are accessible and shell operations such as redirection and piping are also available for use. Modules are like small programs that Ansible pushes out from a control machine to all the nodes or remote hosts. It can be written in the from of command line or in a playbook task. When using command line then we pass command by "-m ". Ansible executes all the modules for installing updates or whatever the required task is, and then removes them when finished. Ansible executes each module, usually on the remote target node, and collects return value in JSON format.
An ansible ad-hoc command is a one-line command that helps you execute simple tasks in a simple yet efficient manner without the need of creating playbooks. Such tasks include copying files between hosts, rebooting servers, adding & removing users and installing a single package. Ansible also gives you the flexibility to create a custom inventory file at your preferred location on your control node to suit your preferences. This is ideal when you have a complex environment and need to segregate your managed nodes into separate inventory files instead of having them all in the hosts file. We've also seen how to gather information from the remote nodes using limiting and filtering parameters. Ansible modules are pieces of code that can be invoked from playbooks and also from the command-line to facilitate executing procedures on remote nodes.
Examples include the apt module, used to manage system packages on Ubuntu, and the user module, used to manage system users. The ping command used throughout this guide is also a module, typically used to test connection from the control node to the hosts. Ansible is a modern and open source IT automation orchestration and provisioning tool which makes your work easier.
You just need to define a list of all instructions you are interested and ansible will go and do it for you. Ansible is always ready to manage your servers, does not matter if it is to install a package, update a configuration or even restart a service. Ansible uses playbook files to describe automation jobs, and playbooks are written in a very simple language called YAML. YAML is a human-readable data serialization language and is commonly used for configuration files, but could be used in many applications where data is being stored. It is very easy for humans to understand, read and write.
Hence the advantage is that even the non-IT support guys can read and understand the playbook and debug if needed. The command module allows administrators to quickly execute remote commands on managed hosts. These commands are not processed by the shell on the managed hosts. As such, they cannot access shell environment variables or perform shell operations, such as redirection and piping. This way you will facilitate resource tracking and collaborate with other sysadmins more easily without having everyone tangled up in a single hosts file. If you need to manage multiple environments, it is safer to have only hosts of a single environment defined per inventory file.
This way, it is harder to accidentally change the state of nodes inside a QA environment when you actually wanted to update some "in production" servers. Ad hoc commands are extremely used in performing quick tasks and tests. They are simple operations that can be run without the need for a playbook file. For example, you can use an ad hoc command to check the disk usage or create a user on a group of servers. Additionally, you could use another ad hoc command to restart a service or update a particular software package.
Ansible uses the default inventory file that is located at /etc/ansible/hosts to reference managed nodes, unless you specify a custom inventory file through the -i option. Ansible is a modern application deployment and configuration management tool that is very powerful and simple to use. It makes it easy to handle thousands of remote servers, also known as managed nodes, from a single control node. Ansible allows you to easily reproduce configuration environments and saves you from logging into individual servers and configuring them one by one.
An Ansible ad hoc command uses the /usr/bin/ansible command-line tool to automate a single task on one or more managed nodes. Ad hoc commands are quick and easy, but they are not reusable. Ad hoc commands demonstrate the simplicity and power of Ansible.
The concepts you learn here will port over directly to the playbook language. Before reading and executing these examples, please read How to build your inventory. You can use the service module to manage services running on the remote nodes managed by Ansible. Using -K will prompt you to provide the sudo password for the connecting user.
You can build from here by adding more tasks and creating complex playbooks, which will make adding large numbers of files quick and easy. Playbooks can be used to define a variety of tasks for the remote hosts to perform, including checking if files and folders exist. This command creates a .yaml file called 'playbook' in the Ansible install folder. We will use tasks in the playbook.yaml file to create files and folders on our remote hosts.
After connecting to your servers, Ansible pushes small programs called "Ansible Modules". Ansible runs that module on your servers and removes them when finished. Information for all servers, such as IP, ssh credentials, etc. is stored in inventory. Ansible uses the hosts file where you can group the hosts and can control the actions on a specific group in the playbooks. For ansible to connect to anything, it needs a 'hosts' file, also called an inventory file, even if it only has one host.
The ansible commands ansible and ansible-playbook lack the option to pass in a single unconfigured host as an argument, so you really do need a hosts file. The host-pattern argument is used to specify the managed hosts on which the ad hoc command should be run. It could be a specific managed host or host group in the inventory.
You have already seen this used in conjunction with the –list-hosts option, which shows you which hosts are matched by a particular host pattern. You have also already seen that you can use the -i option to specify a different inventory location to use than the default in the current Ansible configuration file. Sometimes, you may want to perform quick and simple tasks on remote hosts or servers in Ansible without necessarily having to create a playbook. In that case, you would require to run an ad-hoc command. In the previous two articles of this Ansible Series, we've explained Core Components of Ansible and Setting Up Ansible Control Node.
In this part 3, we will demonstrate how you can configure Ansible managed nodes to run ad-hoc commands on remote hosts. The environment for this lab uses SSH with password authentication to login to the managed nodes. For the sake of keeping things simple the password is put into the inventory file in clear text.
In real world scenarios you would either use SSH key authentication or supply the password in a secure way, e.g. by using Ansible Vault. In Ansible, variables are used to handle differences between managed hosts. Using variables, you can represent variations between systems when executing playbooks or ad hoc commands. For instance, in the previous section we used the ansible_host variable that simply told Ansible where to search for the IP address of a managed node.
Ansible inventory file allows system administrators to keep track of their managed remote systems. The default inventory file is known as the hosts file and is located in the /etc/ansible directory. This is where all the managed remote nodes are specified. Ansible is a modern configuration management tool that facilitates the task of setting up and maintaining remote servers. Build Your Inventory, Running a playbook without an inventory requires several command-line flags.
Also, running This tiny example data center illustrates a basic group structure. Upon installation, Ansible creates an inventory file that is typically located at /etc/ansible/hosts. This is the default location used by Ansible when a custom inventory file is not provided with the -i option, during a playbook or command execution.
Running commands, Limit to one host ansible-playbook playbooks/PLAYBOOK_NAME.yml --limit "host1". Limit to multiple hosts Setting a session limit allows administrators to limit the number of simultaneous sessions per user or per IP address. The "command" and "shell" modules require Python on the managed node.
This is not always possible, although most server systems already have it right after installing the base system. However, we will definitely come across some older devices or systems where Python will not be available, andit would be good to manage them with the same tool. This is possible thanks to the "raw" module, which bypasses the entire subsystem of Ansible modules. He issues the commands directly after establishing the SSH connection, and then sends the result back to us.
This module does not make any attempt to interpret the result or error checking. We'll get whatever is thrown at the output of STDERR and STDOUT. An ad hoc command is a way of executing a single Ansible task quickly, one that you do not need to save to run again later. They are simple, online operations that can be run without writing a playbook. Ad hoc commands are useful for quick tests and changes.
For example, you can use an ad hoc command to make sure that a certain line exists in the /etc/hosts file on a group of servers. You could use another ad hoc command to efficiently restart a service on many different machines or to ensure that a particular software package is up-to-date. In this article, we shed light on how you can configure managed nodes to run Ansible ad-hoc commands to manage remote hosts. This involves the generation of a key pair on the Ansible Control node and copying the Public key to all of the remote hosts. This will be a crucial step going forward and will make your work much easier. They are both a great learning tool and a quick and dirty (because you never document your work with a playbook!) automation solution.
The Ad-Hoc command is the one-liner ansible command that performs one task on the target host. It allows you to execute simple one-line task against one or group of hosts defined on the inventory file configuration. An Ad-Hoc command will only have two parameters, the group of a host that you want to perform the task and the Ansible module to run. This tutorial shows you how to use the Ansible built-in ping module to perform various set variables on remote hosts.
The Ansible ping request is a simple yet useful tool that you can use to test the availability and practicality of remote hosts. When defined using options in ad hoc commands, they take precedence over the directive configured in the Ansible configuration file. The following table shows the analogous command-line options for each configuration file directive. Now you can verify your managed hosts using the ansible-inventory command.
Note that you must reference the full path to the inventory file when using the -i option. By default, all entries are commented out and no hosts are specified. In the next step, you will connect to the remote hosts and create a custom inventory file. The Ad-Hoc command gives you more advantage for exploring ansible itself. Since you often want to run a command or playbook against multiple hosts at once, patterns often refer to inventory groups. Both the ad hoc command and the playbook above will execute against all machines in the webservers group.
This table lists common patterns for targeting inventory hosts and groups. Then, you won't need to provide those parameters in the command line. The Rundeck-Ansible plugin uses the rundeck user as the default user to connect to the Ansible remote inventory nodes. At this point, it's possible to define the SSH authentication method and the specific Ansible SSH user to connect to the remote inventory nodes. You need to define the username in the SSH User textbox. Depending on the auth method you can select the password from the storage path or the ssh key .
