Hosts & the Inventory File
When we run ansible, we see a few warnings on top:
Host file not found
with a path to a host file somewhere on your system. Then it says:
provided hosts list is empty, only localhost is available.
It turns out, at first, we can only execute ansible against one host: localhost.
If you want to start running against any other server, you need to create a host
configuration file. You can either do this in a global hosts file - in the location
described in the warning - or you can create a file right inside your project. That's
the way I like to do it!
In your project, create a new directory called ansible. And inside, make a new
hosts.ini file.
The smallest thing you need to configure a host is... just the IP address: 127.0.0.1:
| 127.0.0.1 |
We'll keep running things against our local machine for a bit longer.
As soon as you have this, you can use this as your host: ansible 127.0.0.1 -m ping.
To tell Ansible about the new hosts file, add -i ansible/hosts.ini. It's -i because
the hosts file is known as your inventory. Try it!
ansible 127.0.0.1 -m ping -i ansible/hosts.ini
Setting Host Variables
Ah! It fails! I keep telling you that Ansible works by connecting over SSH and then running commands. Well, technically, that's not 100% true: you can actually configure Ansible to connect to your server in different ways, though you'll almost always use SSH. The most common exception is when you're working on your local machine - you don't need to connect via SSH at all!
To tell Ansible that this is a local connection, in your hosts.ini file, after
the IP address, add ansible_connection=local:
| 127.0.0.1 ansible_connection=local | |
| // ... lines 2 - 3 |
There's also a docker connection type if you're getting nerdy with Docker.
Try that ping again!
ansible 127.0.0.1 -m ping -i ansible/hosts.ini
Got it!
This little change is actually really important. By saying ansible_connection=local,
we are setting a variable inside of Ansible. And as we build out more complex Ansible
configuration, this idea of setting and using variables will become more important.
As you'll see, you can set more variables for each host, which will let us change
behavior on a host-by-host basis.
In this case, ansible_connection is a built-in variable that Ansible uses when
it connects. We're simply changing it first.
Host Groups
So right now, we have just one host. But eventually, you might have many - like
5 web server hosts, 2 database hosts and a Redis host. One common practice is to
group your hosts. Let me show you: at the top, add a group called [local],
with our one host below it:
| [local] | |
| 127.0.0.1 ansible_connection=local | |
| // ... lines 3 - 4 |
As soon as we do that, instead of using the IP address in the command, we can use the group name:
ansible local -m ping -i ansible/hosts.ini
That will run the module against all hosts inside of the local group... which
is just one right now. Boring! Let's add another! Below the first, add localhost
with ansible_connection=local:
| [local] | |
| 127.0.0.1 ansible_connection=local | |
| localhost ansible_connection=local | |
| // ... lines 4 - 5 |
This is a little silly, but it shows how this works. Run the command now!
ansible local -m ping -i ansible/hosts.ini
Yes! It runs the ping module twice: once on each server. If you needed to setup 10 web servers... well, you can imagine how awesome this could be.
And actually, there's a special option - --list-hosts that can show you all of
the hosts in that group:
ansible local --list-hosts -i ansible/hosts.ini
Ok, remove the localhost line:
| [local] | |
| 127.0.0.1 ansible_connection=local | |
| // ... lines 3 - 4 |
Time to start executing things against a real server.
Hey, nice article.. You can have a look what at this article too https://tunnelix.com/an-age...