Ansible

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# Ansible

<div class="contributors-line">
		Authors: 
<a href="/training-material/hall-of-fame/hexylena/" class="contributor-badge contributor-hexylena"><img src="/training-material/assets/images/orcid.png" alt="orcid logo"/><img src="https://avatars.githubusercontent.com/hexylena?s=27" alt="Avatar">Helena Rasche</a>

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<div class="footnote" style="bottom: 8em;"><i class="far fa-calendar" aria-hidden="true"></i><span class="visually-hidden">last_modification</span> Updated: Apr 6, 2021</div>

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### <i class="far fa-question-circle" aria-hidden="true"></i><span class="visually-hidden">question</span> Questions

- Why Ansible?

- How and when to use Ansible?

- How to write a role?

- How to leverage community build roles?

---

### <i class="fas fa-bullseye" aria-hidden="true"></i><span class="visually-hidden">objectives</span> Objectives

- Learn Ansible basics.

- Write a simple role.

- Install a role from Ansible Galaxy.

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## Configuration Management

Manages the configuration of machines.

Specifies what software is installed, how it is configured

???

- Configuration management manages the configuration of machines.
- It specifies what software should be installed, and how it should be configured

---

### Why Configuration Management?

- Are you keeping track of config changes?
- What if your server dies?
- ... or your VM is accidentally deleted?
- Can you recover? How quickly?

???

- So why do you want configuration management?
- What do you do when things go wrong?
- What if your server dies?
- Did you backup your configuration?
- Did you back up your webserver configuration?
- Ansible provides an answer.

---

### Configuration Management goals

- Reproducibility

- Ensure 1000s of machines are correctly configured

- Easily recover from bad situations

???

- The goals of using CM are reproducibility, uniformity, and recovery.

---

### Ansible

- [Ansible](https://www.ansible.com/) is an open-source configuration management tool, sponsored by Red Hat

- Several [alternatives](https://en.wikipedia.org/wiki/Comparison_of_open-source_configuration_management_software) are available (Chef, Puppet, Salt, etc)

- It uses an agentless model: SSH into machine and executes commands

- Very popular, especially among Galaxy admins!

- Many modules for common tasks like copying files or managing users or services.

???

- Ansible is a very popular CM tool, sponsored by RedHat.
- There are several alternatives, but Galaxy Project uses Ansible.
- It uses an agent-less model. You SSH into machines and execute commands on them.
- It has many popular pre-existing roles for common tasks.

---

## Important Terms

???

- Some important terms you should know

---

### Inventory File

Defines the systems (called "hosts") against which Ansible will work.

```ini
[webservers]
192.168.0.1
192.168.0.2 ansible_user=ubuntu

[databases]
db_1.example.org ansible_user=root
```

???

- First is the Inventory File.
- This file lists all of your hosts.
- The group name is in square brackets.
- Group names are used to select a set of systems, on which Ansible should operate.
- It is possible to assign variables to hosts and groups.
- Here we override the ansible user variable on two hosts.
- This variable controls which user is used in login.

---

### Ansible Module and Tasks

A **module** is a piece of code that Ansible can execute on a host, collecting return values.

A **task** is an invocation of single module with its configuration.

```yaml
---
- copy:
    src: foo.conf
    dest: /etc/foo.conf
    owner: foo
    group: foo
    mode: 0644

- package:
    name: ntpdate
    state: present
```

???

- Here is an example of invoking the copy module and the package module.
- Copy copies a file from source, on the local host to destination, on the remote host.
- Then it sets some attributes about the file like the owner and mode.
- Next we see an example of the package module. This is a generic OS package manager module.
- It ensures that for the package named ntpdate, its state is present, i.e. installed.

---

### Role

.pull-left[
A collection of:

- tasks
- files
- templates
- variables
- handlers

]

.pull-right[
with a predefined directory structure:
```
.
├── defaults
│   └── main.yml
├── files
│   └── cvmfs_wipecache.centos_7
├── handlers
│   └── main.yml
├── meta
│   └── main.yml
├── README.md
├── tasks
│   ├── apache.yml
│   ├── main.yml
│   └── stratumN.yml
├── templates
│   └── stratum1_squid.conf.j2
├── tests
│   ├── inventory
│   └── test.yml
└── vars
    └── main.yml

```
]

???

- A role is a collection of tasks, files, templates, variables, and handlers.
- Tasks are things to be executed, like a copy task to add files to a remote machine.
- Files have static, unchanging files that are used by the tasks.
- The templates are like files, but they contain variables which will be replaced, when ansible deploys the file.
- Variables contain definitions of variables for use in templates and tasks.
- Handlers manage services, restarting them when configuration changes.

---

### Playbook

A YAML file listing a set of tasks and/or roles that should be applied to a group of hosts.

.pull-left[
- We define a playbook which has a name
- And applies to some group of hosts
- We specify some additional variables
- And then invoke some roles
]

.pull-right[
```yaml
- name: CVMFS
  hosts: all
  vars:
    cvmfs_role: client
    galaxy_cvmfs_repos_enabled: true
  roles:
    - geerlingguy.repo-epel
    - galaxyproject.cvmfs
```
]

???

- This is an example playbook.
- We give it a name, in this case CVMFS.
- Then we select some hosts, i.e. all hosts known to our inventory file.
- We specify some additional variables.
- And then we invoke two roles.

---

### Vault

- Ansible playbooks should be kept under **version control** (typically with Git)
- Playbooks can be safely shared on public Git repositories (e.g. GitHub) by storing secrets like passwords in encrypted files called **vaults**

```
$ANSIBLE_VAULT;1.1;AES256
63333238633033313664633437316231323932326531386266636637353037313335613563663934
6639666536653631363739383639633165633337393334630a353233393938646539306362633738
61613439366435336230636561663864323765303663666239613430323534333665636665643964
6537376666323333660a663233343565393166373665366138306661343764623561343634656463
31636265303430623731643766346434323565663436626466353765393465376533376366356463
```

???

- If you have secrets like API keys or passwords, you need to use Vault.
- Vault encrypts your secrets with a password, so you can include them in your playbooks.
- This lets you collaborate on playbooks and infrastructure publicly with git.

---

## Ansible Philosophies

- Some people write a single playbook that completely manages a machine (installing everything on a brand new machine)

- Other people write playbooks for a single task (e.g. upgrading software / installing nginx)

- Which one depends on your use case.

???

- There are multiple ways of designing playbooks, use one that fits your use case.
- Some prefer a playbook which does everything, so no step can be forgotten.
- Others prefer playbooks which do individual steps. These can be faster, and you can only run the ones that change.

---

## Ansible Galaxy

- Public repository of roles

- Many for common software deployment (nginx, apache, postgresql)

- Different "Galaxy" than the bioinformatics tool server (but Ansible can be used to install that too!)

???

- Ansible has a repository for public roles.
- There are a huge number of available roles for common tasks.
- It is called Ansible Galaxy, but it is a different Galaxy.

---
### <i class="fas fa-key" aria-hidden="true"></i><span class="visually-hidden">keypoints</span> Key points

- Ansible lets you do system administration at scale

- Many system administration, software installation, and software management tasks are already available as Ansible tasks or roles

---

## Thank You!

This material is the result of a collaborative work. Thanks to the [Galaxy Training Network](https://training.galaxyproject.org) and all the contributors!

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<a rel="license" href="https://creativecommons.org/licenses/by/4.0/">
This material is licensed under the Creative Commons Attribution 4.0 International License</a>.