Ways of Performing Configuration, Using adhoc command, Using Playbooks, Modules in Ansible , Creating new inventory file , Working with shell Module, user Module & apt Module

adhoc commands  

Important modules in ansible 

1) command – This module is used for executing basic linux commands on managed nodes. 

2) shell –  This module is used to execute commands which involved redirection and piping and to execute shell scripts on managed nodes. 

3) ping  —  This module is used to check if the remote server is pingable or not. 

4) user —  This module is used for user management like create user, setting password, assign home directory  etc 

5) copy  —  This module is used to copy the files and folders from controller to managed nodes 

6) fetch  —  This module is used to copy files and folder from managed nodes to controller 

7) file  —  This module is used for creating or deleting files and folders on managed nodes. 

8) stat  —  Used to capture detailed information about files and folders present in managed nodes. 

9) debug —  Used to display output of any module 

10) apt   —  Used for performing package management on managed nodes ie installing softwares / upgrading repositories etc . It works on ubuntu, debain flavours of linux.  

11) yum  —  similar to apt module. It works on Red hat linux, centos etc 

12) git  —  used to perform git version controlling on managed nodes 

13) replace — This is used to replace specific text in configuration file with some other text. 

14) service  — used for starting / stoping / restarting services on managed nodes. 

15) include  —  Used for calling child play books  from parent play book 

16) uri    — useful in checking  if remote url is reachable or not. 

17) docker_container  —  used to execute docker  commands related to container management on managed nodes 

18) docker_image  —  used to execute commands related to docker images on managed nodes. 

19) docker_login  —  used to login to docker hub from managed nodes. 

20) setup   —  used to capturing system information related to the managed nodes. 

$ ansible all -i /etc/ansible/hosts -m command -a ‘free’ 

$ ansible all -i /etc/ansible/hosts -m command -a ‘touch file1’ 

To check the file which is created 

$ ssh 172.31.2.173    ( this command will go that machine  ) 

$  ls   

$  exit    ( to come back to controller ) 

To install docker in all managed nodes 

 $ ansible all -i /etc/ansible/hosts -m shell -a ‘curl  -fsSL  https://get.docker.com  -o get-docker.sh’    

$ ansible all -i /etc/ansible/hosts -m shell -a ‘sh get-docker.sh’    

+++++++++++++ 

 To check docker is installed or not 

$ ssh 172.31.2.173 

$ docker  –version 

$  exit  (  to come back to controller ) 

+++++++++++++++++ 

Notes: 

Ansible performs remote configurations in 2 ways 

1) using adhoc commands 

2) using play books 

Syntx of adhoc commands 

$ ansible  all/group_name/ipaddress -i  path_of_inventory_file -m modulename  -a  ‘arguments’ 

+++++++++++++++++ 

Ansible command module to check the  memory info on all managed nodes 

$ ansible all -i /etc/ansible/hosts -m command -a ‘free’ 

++++++++++++++++++ 

To open the default inventory file 

$ sudo vim  /etc/ansible/hosts 

( Observation:  3 ip address are available ) 

+++++++++++++++++ 

Now, I copy the first two IP address (  in a  new notepad file ) 

quit the inventory file 

+++++++++++++ 

Create my own inventory file 

$ vim  myinventory 

go to insert mode 

paste two ip address 

save and quit 

+++++++++++ 

To check the inventory file 

$ cat myinventory 

+++++++++++ 

$ ansible all -i myinventory -m command -a ‘free’ 

Observation:  free command works on only two machines 

+++++++++++++ 

If you do not mention the inventory file, it takes default inventory file. 

ex: 

$ ansible all  -m command -a ‘free’ 

+++++++++++++++++++++++++++++++ 

command module is the default module in ansible 

$ ansible all  -a ‘free’ 

++++++++++++++++++++++ 

Note: 

The defualt inventory file is /etc/ansible/hosts  and when using this inventory file, we need not use -i option. 

ex: 

$ ansible all  -m command -a ‘free’ 

The default module  is module. When using command module we need not use -m option 

ex: 

$ ansible all  -a ‘free’ 

Shell Module 

—————- 

ansible command to execute ls  -la  and store the output into  file1 on all the managed nodes. 

$ ansible  all  -m  shell -a ‘ls -la > file2’ 

To check the file which is created 

$ ssh 172.31.12.239 

$ ls 

$ exit   ( to come back to controller ) 

+++++++++++++++ 

command to install docker  on all managed nodes 

$ ansible all  -m shell -a ‘curl  -fsSL  https://get.docker.com  -o get-docker.sh’    

$ ansible all -m shell -a ‘sh get-docker.sh’    

++++++++++++++++++++++++ 

User Module: 

( From controller ) 

To create new user 

$ sudo  useradd sai 

$ vim /etc/passwd     (  User will be created in this file ) 

To set the password 

$ sudo passwd  sai      ( sai is the username) 

+++++++++++ 

Now, i want to create user in all managed nodes 

$ ansible  all -m user  -a  ‘name=anu  password=sunil’ 

( we ger error : permission denied ) 

$ ansible  all -m user  -a  ‘name=anu  password=sunil’  -b  ( become , for higher privileges on managed nodes ) 

++++++++++++++ 

To check if user is create or not 

$  ssh 172.31.12.239 

$ vim  /etc/passwd 

$  exit 

+++++++++++++++++++++ 

Command to create user and set home directory, user id,  default working shell etc 

Another example 

$ ansible all -m user  -a ‘name=Ravi password=freefree uid=1234 comment=”A regular user”  home=/home/ubuntu/Ravi shell=/bin/bash’ -b 

To check for the new user 

$  ssh 172.31.85.232 

$ vim  /etc/passwd 

++++++++++ 

Install git in all managed nodes 

——————————– 

$ ansible all -m apt  -a ‘name=git  state=present’ -b 

Observation:  

We get “changed”: false 

( That means git is already installed on it. The command has no effect in the nodes) 

Now , run the below command 

$ ansible all -m apt  -a ‘name=git  state=absent’ -b 

( absent  means – uninstall ) 

output, we get in yellow color  

( scroll up )  we get  “changed”:true 

( The command is effected the instance ) 

Now if we run the below command  ( with present option ) 

$ ansible all -m apt  -a ‘name=git  state=present’ -b 

we get  “changed”:true  

Notes: 

apt module  — This is used for package management. 

1)  ansible all -m apt  -a ‘name=git  state=present’ -b 

state=present  is for installation 

state=latest    for upgradation 

state=absent    for uninstallation 

++++++++++++++++++++++++++++++++++++++++++ 

I wan to update apt-repositoty and install tomcat8 

ansible all -m  apt -a ‘name=tomcat8 state=present  update_cache=yes’ -b 

The above command will update apt repository and install tomcat8 

To update apt-repository on managed nodes  update_cache=yes  is used  

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