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Ansible
=======
Ansible is a extra-simple Python API for doing 'remote things' over SSH.
Ansible is a extra-simple tool/API for doing 'parallel remote things' over SSH -- whether
executing commands, running declarative 'modules', or executing larger 'playbooks' that
can serve as a configuration management or deployment system.
While [Func](http://fedorahosted.org/func), which I co-wrote, aspired to avoid using SSH and have it's own daemon infrastructure, Ansible aspires to be quite different and more minimal, but still able to grow more modularly over time. This is based on talking to a lot of users of various tools and wishing to eliminate problems with connectivity and long running daemons, or not picking tool X because they preferred to code in Y.
While [Func](http://fedorahosted.org/func), which I co-wrote,
aspired to avoid using SSH and have it's own daemon infrastructure,
Ansible aspires to be quite different and more minimal, but still able
to grow more modularly over time. This is based on talking to a lot of
users of various tools and wishing to eliminate problems with connectivity
and long running daemons, or not picking tool X because they preferred to
code in Y.
Why use Ansible versus something else? (Fabric, Capistrano, mCollective, Func, SaltStack, etc?) It will have far less code, it will be more correct, and it will be the easiest thing to hack on and use you'll ever see -- regardless of your favorite language of choice. Want to only code plugins in bash or clojure? Ansible doesn't care. The docs will fit on one page and the source will be blindingly obvious.
Why use Ansible versus something else? (Fabric, Capistrano, mCollective,
Func, SaltStack, etc?) It will have far less code, it will be more correct,
and it will be the easiest thing to hack on and use you'll ever see --
regardless of your favorite language of choice. Want to only code plugins
in bash or clojure? Ansible doesn't care. The docs will fit on one page
and the source will be blindingly obvious.
Principles
==========
Design Principles
=================
* Dead simple setup
* Super fast & parallel by default
* No server or client daemons, uses existing SSHd
* No additional software required on client boxes
* Everything is self updating on the clients. "Modules" are remotely transferred to target boxes and exec'd, and do not stay active or consume resources.
* Only SSH keys are allowed for authentication
* usage of ssh-agent is more or less required (no passwords)
* plugins can be written in ANY language
* as with Func, API usage is an equal citizen to CLI usage
* use Python's multiprocessing capabilities to emulate Func's forkbomb logic
* all file paths can be specified as command line options easily allowing non-root usage
* Everything is self updating on the clients
* Encourages use of ssh-agent
* Plugins can be written in ANY language
* API usage is an equal citizen to CLI usage
* Can be controlled/installed/used as non-root
Requirements
============
@ -28,16 +39,17 @@ Requirements
For the server the tool is running from, *only*:
* python 2.6 -- or the 2.4/2.5 backport of the multiprocessing module
* PyYAML (if using playbooks)
* paramiko
Inventory file
==============
The inventory file is a required list of hostnames that can be potentially managed by
ansible. Eventually this file may be editable via the CLI, but for now, is
edited with your favorite text editor.
The inventory file is a required list of hostnames that can be
potentially managed by ansible. Eventually this file may be editable
via the CLI, but for now, is edited with your favorite text editor.
The default inventory file (-H) is ~/.ansible_hosts and is a list
The default inventory file (-H) is /etc/ansible/hosts and is a list
of all hostnames to target with ansible, one per line. These
can be hostnames or IPs
@ -66,32 +78,40 @@ Run a module by name with arguments
API Example
===========
The API is simple and returns basic datastructures.
The API is simple and returns basic datastructures. Ansible will keep
track of which hosts were successfully contacted seperately from hosts
that had communication problems. The format of the return, if successful,
is entirely up to the module.
import ansible
runner = ansible.Runner(
runner = ansible.runner.Runner(
pattern='*',
module_name='inventory',
host_list=['xyz.example.com', '...']
module_name='inventory',
module_args='...'
)
data = runner.run()
{
'xyz.example.com' : [ 'any kind of datastructure is returnable' ],
'foo.example.com' : None, # failed to connect,
...
{
'contacted' : {
'xyz.example.com' : [ 'any kind of datastructure is returnable' ],
'foo.example.com' : [ '...' ]
},
'dark' : {
'bar.example.com' : [ 'failure message' ]
}
}
Additional options to Runner include the number of forks, hostname
exclusion pattern, library path, arguments, and so on. Read the source, it's not
complicated.
exclusion pattern, library path, arguments, and so on.
Read the source, it's not complicated.
Patterns
========
To target only hosts starting with "rtp", for example:
* ansible "rtp*" -n command -a "yum update apache"
* ansible -p "rtp*" -n command -a "yum update apache"
Parallelism
===========
@ -107,38 +127,41 @@ File Transfer
Ansible can SCP lots of files to lots of places in parallel.
* ansible -f 10 -n copy -a "/etc/hosts /tmp/hosts"
* ansible -p "web-*.acme.net" -f 10 -n copy -a "/etc/hosts /tmp/hosts"
Bundled Modules
===============
Ansible Library (Bundled Modules)
=================================
See the example library for modules, they can be written in any language
and simply return JSON to stdout. The path to your ansible library is
specified with the "-L" flag should you wish to use a different location
than "~/ansible". There is potential for a sizeable community to build
than "/usr/share/ansible". This means anyone can use Ansible, even without
root permissions.
There is potential for a sizeable community to build
up around the library scripts.
Existing library modules
========================
Modules include:
* command -- runs commands, giving output, return codes, and run time info
* ping - just returns if the system is up or not
* facter - retrieves facts about the host OS
* ohai - similar to facter, but returns structured data
* copy - add files to remote systems
Playbooks
=========
Playbooks are loosely equivalent to recipes or manifests in most configuration
management or deployment tools and describe a set of operations to run on
a set of hosts. Some tasks can choose to only fire when certain
conditions are true, and if a task in a chain fails the dependent tasks
will not proceed. Playbooks are described in (YAML)[http://yaml.org] format.
Future plans
============
* modules for users, groups, and files, using puppet style ensure mechanics
* ansible-inventory -- gathering fact/hw info, storing in git, adding RSS
* ansible-slurp ------ recursively rsync file trees for each host
* very simple option constructing/parsing for modules
* Dead-simple declarative configuration management engine using
a runbook style recipe file, written in JSON or YAML
* maybe it's own fact engine, not required, that also feeds from facter
* add/remove/list hosts from the command line
* list available modules from command line
* filter exclusion (run this only if fact is true/false)
* see TODO.md
License
=======
@ -170,8 +193,8 @@ Mailing List
Author
======
Michael DeHaan -- michael.dehaan@gmail.com
Michael DeHaan -- michael.dehaan@gmail.com
[http://michaeldehaan.net](http://michaeldehaan.net/)
[http://michaeldehaan.net](http://michaeldehaan.net/)