Ansible: Ad Hoc Commands Deep Dive

Ansible Ad Hoc Commands Deep Dive

Ansible: Setup, Configure, and Ad Hoc Commands Deep Dive
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ansible is an opensource tool that enables automate, configure and orchestrate your infrastructure.

How to install Ansible
----------------------
>>  yum list epel-release
>>  yum install epel-release(do it only if not installed)
>>  sudo yum install ansible
>>  sudo yum install git

Configure Ansible Inventory(An inventory is a list of hosts that Ansible manages)
---------------------------
>>  vim /etc/ansible/hosts  (Default Ansible Inventory File)
localhost
vsathyak2 ansible_host=vsathyak2c.mylabserver.com
vsathyak3 ansible_host=vsathyak3c.mylabserver.com

Create a user 'ansible' in Control node
-------------------------------------
>>  sudo useradd ansible(adding user ansible)
>>  sudo passwd ansible(learn@123)

>>  su - ansible
>>  ansible localhost -m ping -k 
SSH password: manu@123

localhost | FAILED! => {
    "msg": "Using a SSH password instead of a key is not possible because Host Key checking is enabled and sshpass 
    does not support this.  Please add this host's fingerprint to your known_hosts file to manage this host."
}

>>  ssh localhost  (do this as ansible user)
>>  ansible localhost -m ping -k 
SSH password: learn@123

localhost | SUCCESS => {
    "ansible_facts": {"discovered_interpreter_python": "/usr/bin/python"}, 
    "changed": false, 
    "ping": "pong"
}

________________________________________________________________________________________________________________________
Configuring SSH and Sudo for Ansible
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Create a user 'ansible' and set password in Host node
-----------------------------------------------------
>>  Connect over ssh to host node from control node
>>  sudo useradd ansible (adding user ansible)
>>  sudo passwd ansible (manu@123)
>>  logout

Sharing preshared key from Control node to Host node
---------------------------------------------------
>>  sudo su - ansible (switching to ansible user)
>>  ssh-keygen (generate ssh keys on Control Node)
>>  ssh-copy-id vsathyak2c.mylabserver.com
>>  Enter ansible user password

Giving sudo privilege to 'ansible' user in Host nodes
-----------------------------------------------------
>>  ssh cloud_user@vsathyak2c.mylabserver.com  from control node or access it from terminal directly.

Note :: /etc/sudoers may be edited to allow 'ansible' user to sudo any commandwithout a password
>>  sudo visudo

Find the line
# %wheel        ALL=(ALL)       NOPASSWD: ALL

Add the following
ansible        ALL=(ALL)       NOPASSWD: ALL

________________________________________________________________________________________________________________________
The Ansible Configuration File
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1. The default ansible configuration is /etc/ansible/ansible.cfg
2. The configuration properties may be overridden using local files.
    A. First file found is used and later one is ignored.
    B. Configuration file is searched in the following order
        a. ANSIBLE_CONFIG (environment variable if set)
        b. ansible.cfg (in current directory)
        c. ~/ansible.cfg (in home directory)
        d. /etc/ansible/ansible.cfg
        
Way to view the ansible config file
-----------------------------------
>>  vim /etc/ansible/ansible.cfg
            OR
>>  man ansible-config
        
________________________________________________________________________________________________________________________
Setting Up the Ansible Inventory
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1. Inventory is a list of hosts that Ansible manages.
2. The default ansible inventory file is /etc/ansible/hosts
3. Inventory location may be specified as follows.
    a. Default /etc/ansible/hosts
    b. Specified by CLI : ansible -i <inventory_file_name>
    c. Can be set in ansible.cfg

You can use default host inventory or you can create a new inventory file.
Create user defined inventory file
----------------------------------
>>  sudo su - ansible
>>  pwd  ==> /home/ansible
>>  cp /etc/ansible/hosts inv  (Copying default inventory to user definced inventory inv)
>>  vim inv

localhost

[all]                --> this defines a group of hosts in ansible called 'all'
localhost
vsathyak2 ansible_host=vsathyak2c.mylabserver.com
vsathyak3 ansible_host=vsathyak3c.mylabserver.com

[centos]             --> this defines a group of hosts in ansible called 'centos'
vsathyak2 ansible_host=vsathyak2c.mylabserver.com
vsathyak3 ansible_host=vsathyak3c.mylabserver.com

[ubuntu]             --> this defines a group of hosts in ansible called 'ubuntu'
vsathyak4 ansible_host=vsathyak4c.mylabserver.com
:wq

>>  ansible localhost -m ping           (ping on the localhost)
>>  ansible -i inv centos -m ping       (ping to all the host under the group centos) 

vsathyak2 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    }, 
    "changed": false, 
    "ping": "pong"
}
vsathyak3 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    }, 
    "changed": false, 
    "ping": "pong"
}

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Ansible Ad Hoc Commands - Understanding Ansible Ad Hoc
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The Ansible Command
-------------------
Syntax:  ansible <HOST> -m <MODULE> -a "ARG1 ARG2 ARG3" -f <NUM_FORKS>

Ping Module   ==> ansible -i inv remote -m ping    [remote is the host group mentioned in user defined inventory:inv]

Setup Module  ==> ansible -i inv remote -m setup   [Give facts about remote host.]

Yum Module    ==> ansible -i inv remote -b -m yum -a "name=elinks state=installed" -f 10  (Installed)
              ==> ansible -i inv remote -b -m yum -a "name=elinks state=absent"           (Uninstalled)
              ==> -i to pass inventory file
              ==> -m to pass module
              ==> -b to pass root privilege
              ==> -a to pass arguments
              ==> -f represents forks, default value is 5
              ==> forks sets number of hosts on which the current task is executed simultaneously
              
________________________________________________________________________________________________________________________
Understanding Ansible Modules
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Modules are discrete units of code that can be used from the command line or in a playbook task
- Modules can take arguments
- Most modules take argument as key=value and delimited by white space.
- man ansible-doc
- Eg: ansible-doc <MODULE>

________________________________________________________________________________________________________________________
The Shell and Command Modules
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The shell and command modules are both effective ways to run raw commands on target host.
- Command Module is the default module used with Ansible ad-hoc when no module is specified.
- Shell module works almost exactly like comman module except commands are ran in a shell environment
- Primary reason to use shell module over command module is for the use of input / output redirection, 
  environment variables or other such shell features.
- As per Ansible doc, best practice is to use command module unless you require shell feature.

Command Module
--------------
>>  ansible vsathyak2 -a "yum install -y elinks"              (No need to specify command module.)
>>  ansible vsathyak2 -m command -a "yum install -y elinks"   (Specified command module here.)
>>  ansible vsathyak2 -m yum -a "name=elinks state=installed" (Using yum module.)
>>  ansible vsathyak2 -a "touch /tmp/file"                    (Creates a file.)
>>  ansible vsathyak2 -a "touch /tmp/file creates=/tmp/file"  ('creates' param will check the file exist. 
                                                               if so, it won't add the file again.)
                                                               
Shell Module
------------
>>  ansible vsathyak2 -m shell -a "echo $PATH > /tmp/file"  (Store Value of PATH variable to /tmp/file)
                                                            (echo '$PATH > /tmp/file' on command module, it wont work)
                                               
________________________________________________________________________________________________________________________
Collecting System Information
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ansible facts are simple various properties and infirmation regarding a given remote system                                                            
- Setup module can retrieve facts
- Facts may be filtered by passing a value for the filter paramater

>>  ansible -i inv vsathyak2 -m setup
>>  ansible -i inv vsathyak2 -m setup | less
>>  ansible -i inv vsathyak2 -m setup -a 'filter=ansible_all_ipv4_addresses' 
>>  ansible -i inv vsathyak2 -m setup -a 'filter=*ipv4*'   (filter support wildcards.)

- Ansible command output may be directed to a file using the --tree output file flag

>>  ansible -i inv <HOST> -m setup --tree <DIRECTORY>
Eg: ansible -i inv centos -m setup --tree facts_dir

>>  cd facts_dir
>>  ls -la   :  2 files, one for each of the host that comes under the server list : centos

________________________________________________________________________________________________________________________
File Manipulation with Ansible
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Working with File Module
------------------------
- File Module can be used to create, delete and modify file properties.
- ansible-doc file (do in terminal to get more infor about file module)
- ansible-doc -s file  

>>  ansible -i inv vsathyak2 -m file -a "name=testfile state=touch" 
    - add file under home dir of ansible user in vsathyak2
    
>>  ansible -i inv vsathyak2 -b -m file -a "name=/root/testfile state=touch"  
    - add file under /root dir in vsathyak2
    - Passed -b flag to provide the root privilege.

>>  ansible -i inv vsathyak2 -b -m file -a "name=testfile state=absent"  
    - absent state will remove the file after its done.
    
Working with Copy Module 
------------------------                                                          
- Copy Module can be used to copy file from number of sources.
  - Control Node to Target Node
  - The file system on the target node.
  - Created during the execution of the copy module and placed on the target nodes.
- ansible-doc copy
- ansible-doc -s copy

>>  ansible -i inv vsathyak2 -m copy -a "src=testfile dest=newfile" 
    - src represents the file or dir name in control node
    - dest represents the file or dir name in host node
    - file from control node get copied to the host vsathyak2 using the above command.
    
>>  ansible -i inv vsathyak2 -m copy -a "src=srcdir dest=destdir" 
    - srcdir is copied to control node under the dir destdir.

>>  ansible -i inv vsathyak2 -m copy -a "src=srcdir dest=." 
    - srcdir is copied to control node with same directory name.

________________________________________________________________________________________________________________________
Editing File Contents with the `lineinfile` Module
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The lineinfile module is a key way of interacting with a files content
- Key feature includes inserting a line of text into a given file
- The module will place the line of text at the end of a file by default. 
- But it can place the line after or before a line of matched text.
- If the module detects the provided text already in place, it will not add it again.
- It will also remove lines a line of text.

>>  ansible -i inv vsathyak2 -m lineinfile -a "path=/home/ansible/testfile line='Hello, VSK' state=present"
    - This will insert the content ''Hello, VSK' to the testfile in the host machine: vsathyak2.
    
>>  ansible -i inv vsathyak2 -m lineinfile -a "path=/home/ansible/testfile line='Hello, Manu' insertbefore=VSK"
    - This will insert the line 'Hello, Manu' before the regex match VSK
    
>>  ansible -i inv vsathyak2 -m lineinfile -a "path=/home/ansible/testfile line='Hello, Vitaly' insertafter=VSK"
    - This will insert the line 'Hello, Vitaly' after the regex match VSK

________________________________________________________________________________________________________________________
Downloading Files with the `get_url` Module
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is frequently necessary to download files from http hosts on managed hosts.
The get_url module provides functionality for downloaded files over http with a variety of options
- http, https and ftp protocols are supported.
- able to perform checksum verification
- support proxy network access
- may use basic or x509 authentication

>>  ansible -i inv vsathyak2 -m get_url -a "url=http://google.com dest=/home/ansible/google.html"
    - dest parameter requires absolute bath.

________________________________________________________________________________________________________________________
Working with File Archives
~~~~~~~~~~~~~~~~~~~~~~~~~~
Archive
--------
The archive and unarchive modules is used for various type of file archives.
- These modules work with common archives such as tar, gz(default), bz2 and zip
- The modules allow for compression of files and directories.

>>  ansible -i inv vsathyak2 -m archive -a "path=/home/ansible format=zip dest=/tmp/files.zip"
    - This will grab all files under /home/ansible, and create a zip files on the dest /tmp/files.zip

Unarchive
---------
>>  ansible -i inv vsathyak2 -m unarchive -a "remote_src=yes  src=/tmp/files.zip dest=/tmp"
    - remote_src=yes indicate the archived file is already on the remote system and not local to the Ansible controller.
    - no need to specify the unzip file format option. It will take care by itself.

________________________________________________________________________________________________________________________
Configuring System Users and Groups
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Creating System Users with the User Module
------------------------------------------
User module may interact with users in many ways.
- Create users
- Remove users
- Change user properties

Add User
--------
>>  ansible -i inv vsathyak2 -b -m user -a "name=super"
>>  ansible -i inv vsathyak2 -b -m user -a "name=super state=present"
    - user named 'super' is created
    - 'b' flag is used since user creation needs root privileges
    - default 'state' is 'present'.

Remove User
-----------
>>  ansible -i inv vsathyak2 -b -m user -a "name=super state=absent"
    - This will remove the user but won't remove the home folder of the user
    
>>  ansible -i inv vsathyak2 -b -m user -a "name=super state=absent remove=yes"
    - This will remove the user all info related to the user
    
________________________________________________________________________________________________________________________    
Working with the Group Module
-----------------------------
Group module works with groups in the same way as the user module interacts with users.

Add Group
--------
>>  ansible -i inv vsathyak2 -b -m group -a "name=consultants"
>>  ansible -i inv vsathyak2 -b -m group -a "name=consultants state=present"
    - group named 'consultants' is created
    - 'b' flag is used since group creation needs root privileges
    - default 'state' is 'present'.
    
Add User and Group
------------------
>>  ansible -i inv vsathyak2 -b -m group -a "name=consultants"     
    - will create the group 'consultants'
    
>>  ansible -i -inv vsathyak2 -b -m user -a "name=super group=consultants"
    - will add the user 'super' to already created group 'consultants'
    
>>  ssh vsathyak2
>>  id super

Remove Group
------------
>>  ansible -i inv vsathyak2 -b -m group -a "name=consultants state=absent"
    - will throw error if any user exist in the group : consultants
    
>>  ansible -i inv vsathyak2 -b -m user -a "name=super group=wheel"
>>  ansible -i inv vsathyak2 -b -m group -a "name=consultants state=absent"
    - Moving user 'super' from group 'consultants' to group 'wheel'
    - Deleting group consultants then.
    
________________________________________________________________________________________________________________________
Installing Software and Daemon Managment
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Installing Software
-------------------
package, yum and apt are used install and manage software packages
- yum and apt are used for distribution specific software management.
- package module will detect teh target host distribution and use the appropriate method of installing software.
- In a mixed distribution environment, package module is the best practice.

package
-------
>>  ansible all -b -m package -a "name=ntpdate state=latest"

>>  ansible all -b -m package -a "name=httpd state=latest"
    - This will throw error if you have an ubuntu based host node since the package name for ubuntu is apache2 and
      apache2 doesnot work for centos based systems.
    - So package module can be used only when all the distros use same name for the software package to be installed.
    
yum
---
>>  ansible -i inv centos -b -m yum -a "name=httpd state=latest"

apt
---
>>  ansible -i inv ubuntu -b -m apt -a "name=apache2 state=latest"    
    

Controlling Daemons with the Service Module
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The service module isused to control system daemons
- It is compatible with both systemd and the older BCD init style of daemon management

To start a service
------------------
>>  ansible -i inv vsathyak2 -b -m service -a "name=httpd state=started enabled=yes"
>>  Go to the server and do systemctl status httpd

To find status a service
------------------------
>>  ansible -i inv vsathyak2 -b -m service -a "name=httpd"

________________________________________________________________________________________________________________________
Managing Long-running Commands
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Async Actions
-------------
. Some operations may require a significant amount of time to execute
. Ansible provide a feature that allows an operation to run asynchronously so that the status may be checked
. There are two options related to running asynchronous commands
  -B used to provide a timeout value and initiate the operation
  -P used to engage on polling of the operation on a set interval
. The status may be checked using the module async_status

>>  vim sleep.sh

#!/bin/sh

sleep 10
echo "I'm done~"
exit

>>  ansible localhost -a "/home/ansible/sleep.sh" -B 15
    This will work since the .sh script executed in 10 sec, ie before the timeout time.
    
>>  ansible localhost -a "/home/ansible/sleep.sh" -B 5
    This will not work since the .sh script executed in 10 sec, but the timeout time is 5 sec.
    
>>  ansible localhost -a "/home/ansible/sleep.sh" -B 20 -P 3
    Here on every 3 second, it will check the status of execution through polling 
    
>>  ansible localhost -a "/home/ansible/sleep.sh" -B 20 -P 0
    Setting 0 to polling will disable polling. 
    
________________________________________________________________________________________________________________________    
Parallelism
~~~~~~~~~~~
Ansible uses the concept called fork to execute tasks in parallel.
Each fork is able to run a task against a target host and by default, ansible executes 5 forks.
Assuming one run a module against 5 hosts, the module should execute near simultaneously on all hosts.
If more than 5 hosts are targeted, hosts after first 5 must wait for a fork to become free before being able to execute.
The number of forks used by ansible is configured oin ansible.cfg or on as-needed basis using -f or --forks flag.

Syntax:  ansible <HOST> -m <MODULE> -a "ARG1 ARG2 ARG3" -f <NUM_FORKS>

>>  ansible all -b -m yum -a "name=elinks state=installed" 
    Say we have 10 hosts machines. Then ansible will install elinks on first 5 first. Then the remaining.

>>  ansible all -b -m yum -a "name=elinks state=installed" -f 10
    Say we have 10 hosts machines. Here ansible will install elinks on all 10 hosts
    
________________________________________________________________________________________________________________________