Talk:Ansible: Difference between revisions
→Inclusions
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* Add entry to Hosts file & enable key less SSH access:
ssh-copy-id -i ~/.ssh/id_rsa.pub aman@server2
* Using the same username is convenient but not required.
= Inventory file =
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= Ansible Config File =
*Variour ansible.cfg files:
/etc/ansible/ansible.cfg
~/.ansible.cfg
ansible.cfg in project directory (takes precedence)
*Contents:
become: Specify how to escalate privileges on the managed host.
become_user: Specify which user account to use on remote host.
become_ask_pass: Whether or not a password should be asked.
inventory: Which Inventory files to be used.
remote_user: Name of user account on the managed host. Not set by default, so local username is used.
*Privilege Escalation
Ansible runs tasks on managed host using same user account as local user, so make sure to copy ssh keys.
Set remote_user in ansible.cfg to specify another user to be used.
If remote_user is not specified, Privilege Escalation can be used.
Enable in [privilege_escalation] section in ansible.cfg:
become=True
become_method=sudo
become_user=root
become_ask_pass=False
Privilege escalation needs sudo configuration
Create a sudo file on all Ansible managed hosts:
nano /etc/sudoers.d/user
user ALL=(ALL) NOPASSWD: ALL
= Adhoc Commands =
* Used for Diagnostics like querying a large number of hosts.
* To quickly make changes to many managed hosts
* Modules are used:
-m Specifies Modules
-a Specifies Arguments
* Default Module can be set in ansible.cfg file.
* 3 Adhoc commands:
command: runs command on managed host
shell: runs command on managed host through the local shell
copy: copy a file, change content on a remote host in a target file
ansible all -i inventory -m command -a id
ansible all -i inventory -m command -a id -o
ansible all -i inventory -m command -a env
ansible all -i inventory -m shell -a env
ansible server1 -m copy -a 'content="Ansible Managed\n" dest=/etc/motd'
= Modules =
List Modules:
ansible-doc -l
Module Help:
ansible-doc <modulesname>
Create sample config:
ansible-doc -s <modulesname>
Using Modules:
ansible all -i inventory -m ping
ansible -i inventory -m ping all
Using in Playbooks:
<pre>
tasks:
- name: Install a package
yum:
name: vsftpd
state: latest
</pre>
= YAML =
* YAML(YAML Ain't Markup Language) structures are represented by indentation.
* Data elements at same hierarchy level should be at same indentation level.
* Do not use Tabs for indentation.
* It is common but not mandatory to start YAML file with 3 dashes & end it with 3 dots.
* This allows YAML code to be placed in some other code.
* Example:
<pre>
---
# example playbook
item1:
parameter1
parameter2
option1
option2
item2
parameter3
...
</pre>
== YAML Contents ==
* Dictionary: key/value pair written in key: value notation
* Lists: represent a list of items, enumerated as '''- item'''. Space after - is mandatory.
* Strings can be enclosed in single or double quotes but that is not mandatory.
* In a multi-line string, first line is ended by | or >. Next lines are indented.
* Verify YAML syntax:
ansible-playbook --syntax-check mycode.yaml
* Dry Run:
ansible-playbook -C mycode.yaml
* Step-by-Step:
ansible-playbook --step mycode.yaml
= Playbook =
* Tasks are performed by Modules.
* Ordering is important: Plays & Tasks are executed in the order they are presented.
* Playbooks do not change anything if the host is already in desired state.
* Avoid modules like command, shell & raw as they are not idempotent by nature.
== Task Attribute ==
* Most important Attribute is Task attribute:
<pre>
tasks:
- name: run service
service: name=vsftpd enabled=true
</pre>
* Here '-' marks beginning of a list of attributes.
* If multiple tasks are defined, each first attribute of task starts with '-'.
== Other Attributes ==
name: specify a specific label to play
hosts: uses patterns to define on which hosts to run a play
remote_user: overwrites the remote_user setting in ansible.cfg
become: overwrites the become setting in ansible.cfg
become_method: overwrites the become_method setting in ansible.cfg
become_user: overwrites the become_user setting in ansible.cfg
= Variables =
* Used for repeated tasks like:
Creating users
Removing files
Installing packages
* Names must start with letters
* Can be defined at a lot of levels
* Can be defined with different scope:
Global Scope: Set from CLI or ansible configuration file
Play Scope: Defined in playbook
Host Scope: Set on groups or Individual hosts through inventory file.
* Variables defined at highest level wins: Global scope wins from host scope
== Defining Variables ==
* Defining in Playbook:
<pre>
- hosts: all
vars:
user: test
home: /home/test
</pre>
* Using variable files:
<pre>
- hosts: all
vars_files:
- vars/users.yml
$ cat vars/users.yml
user: test
home: /home/test
user: test2
home: /home/test2
</pre>
== Using Variables ==
<pre>
tasks:
- name: Creates the user {{user}}
user:
name: "{{ user }}"
</pre>
== Host and Group Variables ==
Host Variable: Applies to one host defined in Inventory file.
Group Variable: Applies to multiple hosts defined in Inventory file.
* Depricated method: Define them in Inventory file:
[webservers]
webserver.example.com
[webservers:vars]
user=test
* Recommended method: Use group_vars & host_vars directories in project directory which contains inventory file.
nano group_vars/webservers
nano host_vars/server01
* Variables can be overwritten from CLI using
ansible-playbook -e "key=value"
== Arrays ==
* Define multiple values
* Refer to these using: users.test.first_name
users:
test:
first_name: test
last_name: done
home_dir: /home/test
test2:
first_name: test2
last_name: done
home_dir: /home/test2
= Facts =
* Contain discovered information about a host
* Can be used in conditional statements to make sure certain tasks run only if they are necessary.
* Setup module is used to gather fact information
ansible -i inventory servers -m setup
* Facts provide a lot of information, Filter them:
ansible -i inventory servers -m setup -a 'filter=ansible_kernel'
* Custom facts can be created to display information about a host.
* Create a file on the Managed Host:
sudo nano /etc/ansible/facts.d/servers.fact
[server_info]
profile = web_server
Check the facts:
ansible -i inventory servers -m setup -a 'filter=ansible_local'
= Inclusions =
* These make it easy to create a modular Ansible Setup.
* Main variables can be set in the master Ansible file, generic tasks can be defined in included files.
* Tasks can be included in a playbook from external YAML file using '''include''' directive.
* Variables can be included from YAML or JSON file using '''include_vars''' directive.
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