Quickly prepare (development) environment with Ansible.
= Workstation
..is a box with some operating system and personal tools needeed to do the job.
The basic stuff I expect to see on every Linux machine:
(browser: all firefox, google-chrome) git hg vim
On Windows the list is same, except vim is replaced with Far Manager + Colorer.
== Workstation: Linux, Ubuntu 13.04
git hg vim
google-chrome
= Bootstraping workstations == ..with Ansible on Linux (Ubuntu 13.04)
Too long/didn't read:
sudo apt-get install ansible git clone git://github.com/techtonik/workstation.git ./workstation/ansible.sh
== ..details == Feel free to skip ..details it's about basic concepts. You may start with example and return when ready.
=== command line tool ===
ansible is a command line tool that run stuff on
remote host. Stuff is packed into modules (-m), and
fine-tuned (selected) using module arguments (-a).
Default module is command, so these two commands
that execute uname on all configured hosts are equal:
ansible '*' -i ansible/hosts -a uname ansible all -i ansible/hosts -m command -a uname
To ping all configured hosts, execute ping module:
ansible all -i ansible/hosts -m ping
=== inventory ===
This hosts file is called "inventory file" and holds
network description. It is usually located at
/etc/ansible/hosts, but can be anywhere (-i option).
$ cat ansible/hosts localhost
Inventory file is required - you can't run commands on arbitrary machine - it should be present in inventory. This might keep you from mistake, but the real reason is that everything in ansible is build around server names and groups in inventory.
=== inventory for playbook === It is because the primary function of Ansible is running playbooks, not single commands. Playbook is a config file in YAML format that (unlike shell script) can be automatically parsed, checked and changed with tools that can handle YAML. Ansible is one such tool.
Playbooks usually contain rules or commands (tasks) that are executed on specific hosts. Host list is a requires attribute of any playbook - the list can be hardcoded or sent as parameter. Rules in playbook often require that specific kinds of servers are present (database, for example) so the rules are very tightly interconnected and tied to the structure of your inventory. It would be rather hard to specify all those servers each time on the command line.
=== remote and local execution === Ansible runs playbooks over network. It takes playbook from local machine, connects to remote machine through SSH and executes instructions there.
SSH access is not necessary when you executing
commands on local machine, but you need to specify
--connection local from command line explicitly. It
is possible to specify connection in hosts.
$ cat ansible/hosts localhost ansible_connection=local
=== documentation === Ansible docs are located at: http://www.ansibleworks.com/docs/
+-- WIP --
Comparison - Chef Cookbooks // Ansible Playbooks:
[ ] reusability
[ ] cross-platformedness
[ ] availability
[ ] dependent books
Questions:
[ ] when you don't know exact package names to
install 'vim' and 'mysql' on different systems
(Fedora: vim-enhanced and community-mysql)
/-- WIP --
== ..example == === 1. install Ansible
-
Ubuntu (13.10, Ansible 1.3):
sudo apt-get install ansible
The 1.3 version is not available for Ubuntu 13.10, so you need to install it from backports. I install it from my own ppa:techtonik/ansible
-
Fedora (19, Ansible 1.3):
sudo yum install ansible
=== 2. create hosts configuration file
$ vim ansible/hosts
The contents of the file for my machine:
$ cat ansible/hosts localhost
=== 3. run Ansible locally
$ ansible localhost -i ansible/hosts -a uname localhost | FAILED => SSH encountered an unknown error during the connection.
This means that Ansible tries to connect through SSH and it is not working. For local machine SSH is not necessary:
$ ansible localhost -i ansible/hosts -c local -a uname localhost | success | rc=0 >> Linux
Here localhost is a mask - you can use '*' or 'all'
to run command on every host from inventory file.
-a uname is a parameter to default command module
that executes uname. -c local makes Ansible
execute all commands locally.
To avoid typing -c local every time, connection type
for localhost can be specified in ansible/hosts:
$ cat ansible/hosts localhost ansible_connection=local
== 4. explore modules
Ansible commands are grouped into modules. For example,
there is a module named ping to check connections:
$ ansible localhost -i ansible/hosts -m ping localhost | success >> { "changed": false, "ping": "pong" }
"changed" value contains Ansible guess if machine state was changed or not. "ping" is a result specific to ping module, which is a standard "pong" response.
For a list of Ansible modules see: http://www.ansibleworks.com/docs/modules.html
=== 4. run playbook
Playbook contains commands to run on specific hosts or
groups of hosts configured in inventory file. To run
playbook, use ansible-playbook command. Playbooks
already specify which hosts they need to run commands
on, so you don't need to do this from command line.
Playbook is written in subset of YAML format.
$ cd ansible
Create playbook:
- hosts: localhost
tasks:
- name: require git, mercurial and subversion apt: pkg=git apt: pkg=mercurial apt: pkg=subversion
Run playbook:
$ ansible-playbook -i hosts playbook.yml
This playbook executes apt module which checks if a
given package is installed and installs it. Note that
it still needs inventory file to operate.
To avoid passing -i hosts every time, it may be
possible to create ansible.cfg configuration file in
playbook directory after [ ] ansible issue #5115 is
fixed.
$ cd .. $ vim ansible/ansible.cfg $ cat ansible/ansible.cfg [defaults] hostfile = ./hosts
And it still won't help, because relative path to hosts file is not properly expanded too at the moment. Need another bug to fill after.
http://www.ansibleworks.com/docs/intro_configuration.html
==== playbook syntax is YAML
The '---' separator marks the start of the 'playbook', ' - ' is an list element (like HTML