learnxinyminutes-docs/ansible.html.markdown

---
category: tool
tool: ansible
contributors:
    - ["Jakub Muszynski" , "http://github.com/sirkubax"]
filename: LearnAnsible.txt
---

Ansible is (one of the many) orchestration tools. It allows you to controll your environment (infrastructure and a code) and automate the manual tasks.
'You can think as simple as writing in bash with python API :)
Of course the rabit hole is way deeper.'

Ansible have great integration with multiple operating systems (even Windows) and some hardware (switches, Firewalls, etc). It has multiple tools that integrate with the could providers. Almost every worth-notice cloud provider is present in the ecosystem (AWS, Azure, Google, DigitalOcean, OVH, etc...)


## Ansible naming and basic concept

### Naming

#### Inventory
Inventory is a set of objects/hosts against which we are executing our playbooks 
For this few minutes, lets asume that we are using default ansible inventory (which in Debian based system is placed in /etc/ansible/hosts_

#### Module - this is name for an logical program (usaly python) that consume proper JSON input and return proper output :)
This program perform certain task/action (like manage Amazon instances, execute shell command, any of your program).
Example: Module:shell - a module that executes shell command on a delegated host(s).
Example: Module:file - performs file operations (stat, link, dir, ...) 

##### Task
Execution of a single module is called a `task`

The simplest module is called `ping`. 
Another example of the module that allow you to execute command remotly on multiple resources is called shell. It is the same as you would execute command remotely over ssh.

Example of a Task run in CLI:
###### Run a ansible module

```bash
$ ansible -m ping hostname_or_a_group_name
$ ansible -m shell -a 'date; whoami' hostname_or_a_group_name
```

another module - `command` that allows to execute a single command only with a simple shell #JM
We should also mention a module `raw` 

```bash
$ ansible -m command -a 'date; whoami' # FAILURE

$ ansible -m command -a 'date'
$ ansible -m command -a 'whoami'
```

##### Playbook

A common way to execute tasks is called `playbook`.
You have to define a list (or group) of hosts that is executed against, some `task(s)` or `role(s)` that are going to be executed. There are also multiple optional settings (like default variables, and way more).

You can think that it is very advanced CLI script that you are executing.

Example of the playbook:

```yml
hosts: all

tasks:
  - name: "ping all"
    ping:
  - name: "execute a shell command"
    shell: "date; whoami; df -h;"
```

You can execute a playbook with a command:
```bash
$ ansible-playbook path/name_of_the_playbook.yml
```

### Basic ansible commands

There are few commands you should know about

`ansible` (to run modules in CLI)
`ansible-playbook` (to run playbooks)
`ansible-vault` (to manage secrets)
`ansible-galaxy` (to install roles from github/galaxy)
and other!

### More on ansible concept

### ansible-roles (a 'template-playbooks in right structure')

There are tasks (modules) that can be run via CLI
The execution plans of multiple tasks (with variables and logic) are called playbooks.

For parts of the code, that should be reusable, a concept called `role` was introduced

Role is a structured way to keep your set of tasks, variables, handlers, default settings, and way more (meta, files, templates).
Role allows to reuse the same parts of code in multiple plybooks (you can parametrize this).
It is a great way to introduce `object oriented` management for your applications.

Role can be included in your playbook (executed in your playbook).


```yml
hosts: all

tasks:
    - name: "ping all"
      ping:
    - name: "execute a shell command"
      shell: "date; whoami; df -h;"

role: 
    - some_role
    - { role: another_role, some_variable: 'learnxiny', tags: ['my_tag'] }

pre_tasks:
    - name: some pre-task
      shell: echo 'this task is the last, but would be executed before roles, and before tasks'
```

```
roles/
   some_role/
     defaults/
     files/
     templates/
     tasks/
     handlers/
     vars/
     meta/
```

#### Role Handlers
Handlers are a task that can be triggered (notified) during execution of a playbook, but they itself execute at the very end of a playbook.
It is a best way to restart a service, check if application port is open, etc.

### ansible - variables
lookup's

### ansible-vault

### inventory

### dynamic inventory

### Jinja2 and templates
jinja filters

### ansible profiling - callback

### facts-cache and ansible-cmdb

### debugging ansible

### Infrastructure as a code - what about Ansible
virtualenv

### ansible - dynamic in AWS

### create instance in AWS

### create env in AWS

## Bonus

### writing own module

### Python API

### Web-UI: Ansible Tower, Jenkins, Rundeck


### Tips and tricks
AND,XOR
--check --diff
tags
meta
no_logs


## Main cons and pros

### Cons

It is an agent-less tool - every agent consumes up to 16MB ram - in some environments, it may be noticable amount.
It is agent-less - you have to verify your environment consistency 'on-demand' - there is no built-in mechanism taht would warn you about some change automatically (this can be achieved with reasonable effort - but it must be known)
Official GUI Tool (web inferface) - Ansible Tower - is more than GUI, but it is expensive. There is no 'small enterprice' payment plan. Easy workaround with Rundeck or Jenkins is possible with reasonable workload.

### Pros

It is an agent-less tools :) In most scenarios, it use ssh as a transport layer. 
In some way you can use it as 'bash on steroids'.
It is very-very-very easy to start. If you are familiar with ssh concept - you already know ansible :) (almost). My personal record is: 'I did show how to install and use ansible (for simple raspberry pi cluster management) and it tool me 30 seconds to deliver a working tool !!!)'
I do provide a training services - I'm able to teach a production-ready person - in 8 hours (1 training day)! It covers all needed to work aspects! No other tool can match this ease of use!
It executes when you do it - other tools (salt, puppet, chef - might execute in different scenario than you would expect)
Documentation is at the world-class standard!
The comunity (github, stackOverflow) would help you very fast.
Writing own modules and extension is fairly easy.


### Neutral
Migration Ansible<->Salt is failrly easy - so if you would need an event-driven agent environment - it would be a good choice to start quick with Ansible, and convert to salt when needed.

## Basics on ansible

Ansible uses ssh or paramiko as a transport layer. In a way you can imagine that you are using a ssh with API to perform your action.
In the 'low-level' way you can use it to execute remote command in more controlled way (still using ssh). 
On the other hand - in advanced scope - you can use python anible code as a library to your own python scrips! This is awesome! (if you know what you are doing). It is a bit like fabric then.

But ansible is way more! It provides an execution plans, an API, library, callbacks, not forget to mention - COMUNITY! and great support by developers!




---
Github template placeholder - to be removed

### Centralized Versioning VS Distributed Versioning

* Centralized version control focuses on synchronizing, tracking, and backing 
up files.
* Distributed version control focuses on sharing changes. Every change has a 
unique id.
* Distributed systems have no defined structure. You could easily have a SVN 
style, centralized system, with git.

[Additional Information](http://git-scm.com/book/en/Getting-Started-About-Version-Control)

### Why Use Git?

* Can work offline.
* Collaborating with others is easy!
* Branching is easy!
* Branching is fast!
* Merging is easy!
* Git is fast.
* Git is flexible.

## Git Architecture

### Repository

A set of files, directories, historical records, commits, and heads. Imagine it
as a source code data structure, with the attribute that each source code
"element" gives you access to its revision history, among other things.

A git repository is comprised of the .git directory & working tree.

### .git Directory (component of repository)

The .git directory contains all the configurations, logs, branches, HEAD, and 
more.
[Detailed List.](http://gitready.com/advanced/2009/03/23/whats-inside-your-git-directory.html)

### Working Tree (component of repository)

This is basically the directories and files in your repository. It is often
referred to as your working directory.

### Index (component of .git dir)

The Index is the staging area in git. It's basically a layer that separates 
your working tree from the Git repository. This gives developers more power 
over what gets sent to the Git repository.

### Commit

A git commit is a snapshot of a set of changes, or manipulations to your 
Working Tree. For example, if you added 5 files, and removed 2 others, these 
changes will be contained in a commit (or snapshot). This commit can then be 
pushed to other repositories, or not!

### Branch

A branch is essentially a pointer to the last commit you made. As you go on
committing, this pointer will automatically update to point the latest commit.

### Tag

A tag is a mark on specific point in history. Typically people use this
functionality to mark release points (v1.0, and so on)

### HEAD and head (component of .git dir)

HEAD is a pointer that points to the current branch. A repository only has 1 
*active* HEAD.  
head is a pointer that points to any commit. A repository can have any number 
of heads.

### Stages of Git
* Modified - Changes have been made to a file but file has not been committed 
to Git Database yet
* Staged - Marks a modified file to go into your next commit snapshot
* Committed - Files have been committed to the Git Database

### Conceptual Resources

* [Git For Computer Scientists](http://eagain.net/articles/git-for-computer-scientists/)
* [Git For Designers](http://hoth.entp.com/output/git_for_designers.html)

## Commands

### init

Create an empty Git repository. The Git repository's settings, stored 
information, and more is stored in a directory (a folder) named ".git".

```bash
$ git init
```

### config

To configure settings. Whether it be for the repository, the system itself,
or global configurations ( global config file is `~/.gitconfig` ).

```bash
# Print & Set Some Basic Config Variables (Global)
$ git config --global user.email "MyEmail@Zoho.com"
$ git config --global user.name "My Name"
```

[Learn More About git config.](http://git-scm.com/docs/git-config)

### help

To give you quick access to an extremely detailed guide of each command. Or to
just give you a quick reminder of some semantics.

```bash
# Quickly check available commands
$ git help

# Check all available commands
$ git help -a

# Command specific help - user manual
# git help <command_here>
$ git help add
$ git help commit
$ git help init
# or git <command_here> --help
$ git add --help
$ git commit --help
$ git init --help
```

### ignore files

To intentionally untrack file(s) & folder(s) from git. Typically meant for
private & temp files which would otherwise be shared in the repository.
```bash
$ echo "temp/" >> .gitignore
$ echo "private_key" >> .gitignore
```

### status

To show differences between the index file (basically your working copy/repo)
and the current HEAD commit.

```bash
# Will display the branch, untracked files, changes and other differences
$ git status

# To learn other "tid bits" about git status
$ git help status
```

### add

To add files to the staging area/index. If you do not `git add` new files to 
the staging area/index, they will not be included in commits!

```bash
# add a file in your current working directory
$ git add HelloWorld.java

# add a file in a nested dir
$ git add /path/to/file/HelloWorld.c

# Regular Expression support!
$ git add ./*.java
```

This only adds a file to the staging area/index, it doesn't commit it to the
working directory/repo.

### branch

Manage your branches. You can view, edit, create, delete branches using this 
command.

```bash
# list existing branches & remotes
$ git branch -a

# create a new branch
$ git branch myNewBranch

# delete a branch
$ git branch -d myBranch

# rename a branch
# git branch -m <oldname> <newname>
$ git branch -m myBranchName myNewBranchName

# edit a branch's description
$ git branch myBranchName --edit-description
```

### tag

Manage your tags

```bash
# List tags
$ git tag

# Create a annotated tag
# The -m specifies a tagging message,which is stored with the tag.
# If you don’t specify a message for an annotated tag,
# Git launches your editor so you can type it in.
$ git tag -a v2.0 -m 'my version 2.0'

# Show info about tag
# That shows the tagger information, the date the commit was tagged,
# and the annotation message before showing the commit information.
$ git show v2.0

# Push a single tag to remote
$ git push origin v2.0

# Push a lot of tags to remote
$ git push origin --tags
```

### checkout

Updates all files in the working tree to match the version in the index, or 
specified tree.

```bash
# Checkout a repo - defaults to master branch
$ git checkout

# Checkout a specified branch
$ git checkout branchName

# Create a new branch & switch to it
# equivalent to "git branch <name>; git checkout <name>"

$ git checkout -b newBranch
```

### clone

Clones, or copies, an existing repository into a new directory. It also adds
remote-tracking branches for each branch in the cloned repo, which allows you 
to push to a remote branch.

```bash
# Clone learnxinyminutes-docs
$ git clone https://github.com/adambard/learnxinyminutes-docs.git

# shallow clone - faster cloning that pulls only latest snapshot
$ git clone --depth 1 https://github.com/adambard/learnxinyminutes-docs.git

# clone only a specific branch
$ git clone -b master-cn https://github.com/adambard/learnxinyminutes-docs.git --single-branch
```

### commit

Stores the current contents of the index in a new "commit." This commit 
contains the changes made and a message created by the user.

```bash
# commit with a message
$ git commit -m "Added multiplyNumbers() function to HelloWorld.c"

# automatically stage modified or deleted files, except new files, and then commit
$ git commit -a -m "Modified foo.php and removed bar.php"

# change last commit (this deletes previous commit with a fresh commit)
$ git commit --amend -m "Correct message"
```

### diff

Shows differences between a file in the working directory, index and commits.

```bash
# Show difference between your working dir and the index
$ git diff

# Show differences between the index and the most recent commit.
$ git diff --cached

# Show differences between your working dir and the most recent commit
$ git diff HEAD
```

### grep

Allows you to quickly search a repository.

Optional Configurations:

```bash
# Thanks to Travis Jeffery for these
# Set line numbers to be shown in grep search results
$ git config --global grep.lineNumber true

# Make search results more readable, including grouping
$ git config --global alias.g "grep --break --heading --line-number"
```

```bash
# Search for "variableName" in all java files
$ git grep 'variableName' -- '*.java'

# Search for a line that contains "arrayListName" and, "add" or "remove"
$ git grep -e 'arrayListName' --and \( -e add -e remove \)
```

Google is your friend; for more examples
[Git Grep Ninja](http://travisjeffery.com/b/2012/02/search-a-git-repo-like-a-ninja)

### log

Display commits to the repository.

```bash
# Show all commits
$ git log

# Show only commit message & ref
$ git log --oneline

# Show merge commits only
$ git log --merges

# Show all commits represented by an ASCII graph
$ git log --graph
```

### merge

"Merge" in changes from external commits into the current branch.

```bash
# Merge the specified branch into the current.
$ git merge branchName

# Always generate a merge commit when merging
$ git merge --no-ff branchName
```

### mv

Rename or move a file

```bash
# Renaming a file
$ git mv HelloWorld.c HelloNewWorld.c

# Moving a file
$ git mv HelloWorld.c ./new/path/HelloWorld.c

# Force rename or move
# "existingFile" already exists in the directory, will be overwritten
$ git mv -f myFile existingFile
```

### pull

Pulls from a repository and merges it with another branch.

```bash
# Update your local repo, by merging in new changes
# from the remote "origin" and "master" branch.
# git pull <remote> <branch>
$ git pull origin master

# By default, git pull will update your current branch
# by merging in new changes from its remote-tracking branch 
$ git pull

# Merge in changes from remote branch and rebase
# branch commits onto your local repo, like: "git fetch <remote> <branch>, git 
# rebase <remote>/<branch>"
$ git pull origin master --rebase
```

### push

Push and merge changes from a branch to a remote & branch.

```bash
# Push and merge changes from a local repo to a
# remote named "origin" and "master" branch.
# git push <remote> <branch>
$ git push origin master

# By default, git push will push and merge changes from
# the current branch to its remote-tracking branch 
$ git push

# To link up current local branch with a remote branch, add -u flag:
$ git push -u origin master
# Now, anytime you want to push from that same local branch, use shortcut:
$ git push
```

### stash

Stashing takes the dirty state of your working directory and saves it on a 
stack of unfinished changes that you can reapply at any time.

Let's say you've been doing some work in your git repo, but you want to pull
from the remote. Since you have dirty (uncommited) changes to some files, you
are not able to run `git pull`. Instead, you can run `git stash` to save your
changes onto a stack!

```bash
$ git stash
Saved working directory and index state \
  "WIP on master: 049d078 added the index file"
  HEAD is now at 049d078 added the index file
  (To restore them type "git stash apply")
```

Now you can pull!

```bash
git pull
```
`...changes apply...`

Now check that everything is OK

```bash
$ git status
# On branch master
nothing to commit, working directory clean
```

You can see what "hunks" you've stashed so far using `git stash list`.
Since the "hunks" are stored in a Last-In-First-Out stack, our most recent 
change will be at top.

```bash
$ git stash list
stash@{0}: WIP on master: 049d078 added the index file
stash@{1}: WIP on master: c264051 Revert "added file_size"
stash@{2}: WIP on master: 21d80a5 added number to log
```

Now let's apply our dirty changes back by popping them off the stack.

```bash
$ git stash pop
# On branch master
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#
#      modified:   index.html
#      modified:   lib/simplegit.rb
#
```

`git stash apply` does the same thing

Now you're ready to get back to work on your stuff!

[Additional Reading.](http://git-scm.com/book/en/v1/Git-Tools-Stashing)

### rebase (caution)

Take all changes that were committed on one branch, and replay them onto 
another branch.
*Do not rebase commits that you have pushed to a public repo*.

```bash
# Rebase experimentBranch onto master
# git rebase <basebranch> <topicbranch>
$ git rebase master experimentBranch
```

[Additional Reading.](http://git-scm.com/book/en/Git-Branching-Rebasing)

### reset (caution)

Reset the current HEAD to the specified state. This allows you to undo merges,
pulls, commits, adds, and more. It's a great command but also dangerous if you 
don't know what you are doing.

```bash
# Reset the staging area, to match the latest commit (leaves dir unchanged)
$ git reset

# Reset the staging area, to match the latest commit, and overwrite working dir
$ git reset --hard

# Moves the current branch tip to the specified commit (leaves dir unchanged)
# all changes still exist in the directory.
$ git reset 31f2bb1

# Moves the current branch tip backward to the specified commit
# and makes the working dir match (deletes uncommited changes and all commits
# after the specified commit).
$ git reset --hard 31f2bb1
```

### reflog (caution)

Reflog will list most of the git commands you have done for a given time period,
default 90 days.

This give you the a change to reverse any git commands that have gone wrong
for instance if a rebase is has broken your application.

You can do this:

1. `git reflog` to list all of the git commands for the rebase
```
38b323f HEAD@{0}: rebase -i (finish): returning to refs/heads/feature/add_git_reflog
38b323f HEAD@{1}: rebase -i (pick): Clarify inc/dec operators
4fff859 HEAD@{2}: rebase -i (pick): Update java.html.markdown
34ed963 HEAD@{3}: rebase -i (pick): [yaml/en] Add more resources (#1666)
ed8ddf2 HEAD@{4}: rebase -i (pick): pythonstatcomp spanish translation (#1748)
2e6c386 HEAD@{5}: rebase -i (start): checkout 02fb96d
```
2. Select where to reset to, in our case its `2e6c386`, or `HEAD@{5}`
3. 'git reset --hard HEAD@{5}' this will reset your repo to that head
4. You can start the rebase again or leave it alone.

[Additional Reading.](https://git-scm.com/docs/git-reflog)

### revert

Revert can be used to undo a commit. It should not be confused with reset which 
restores the state of a project to a previous point. Revert will add a new 
commit which is the inverse of the specified commit, thus reverting it.

```bash
# Revert a specified commit
$ git revert <commit>
```

### rm

The opposite of git add, git rm removes files from the current working tree.

```bash
# remove HelloWorld.c
$ git rm HelloWorld.c

# Remove a file from a nested dir
$ git rm /pather/to/the/file/HelloWorld.c
```

## Further Information

* [tryGit - A fun interactive way to learn Git.](http://try.github.io/levels/1/challenges/1)

* [Learn Git Branching - the most visual and interactive way to learn Git on the web](http://learngitbranching.js.org/)

* [Udemy Git Tutorial: A Comprehensive Guide](https://blog.udemy.com/git-tutorial-a-comprehensive-guide/)

* [Git Immersion - A Guided tour that walks through the fundamentals of git](http://gitimmersion.com/)

* [git-scm - Video Tutorials](http://git-scm.com/videos)

* [git-scm - Documentation](http://git-scm.com/docs)

* [Atlassian Git - Tutorials & Workflows](https://www.atlassian.com/git/)

* [SalesForce Cheat Sheet](http://res.cloudinary.com/hy4kyit2a/image/upload/SF_git_cheatsheet.pdf)

* [GitGuys](http://www.gitguys.com/)

* [Git - the simple guide](http://rogerdudler.github.io/git-guide/index.html)

* [Pro Git](http://www.git-scm.com/book/en/v2)

* [An introduction to Git and GitHub for Beginners (Tutorial)](http://product.hubspot.com/blog/git-and-github-tutorial-for-beginners)