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Day 13

  • Connect to OS1 and OS2.
  • Set the sshd to turn on password authentication
  • Now restart the service sshd
  • and now try to connect to OS2 using OS1 using this command
ssh [email protected] cal
  • We can also switch the order of module and key
ansible a -u ec2-user -k -m command -a "date"
  • Idempotency is used to check weather a software is installed or not
  • Shell module is used to execute shell commands
  • -a is for argument of a module
ansible a -u ec2-user -k -m yum -a "name=httpd state=present"
  • yum module takes name of the software using name varibale and state to install the software.
ansible localhost -m yum -a "name=httpd state=present"
  • Service module is used to check or start a service.
ansible localhost -m service -a "name=httpd state=started"
  • To copy a file we use copy module.
  • src is used to specify where is the file in your base machine
  • dest is used to specify where to put file in your destination machines.
ansible localhost -m copy -a "src=index.html dest=/var/www/html"
  • Since to do every task with specifying a command we can also use a playbook to specify all the commands.
  • To write playbook in Ansible we use yaml file yet another markup language
  • Yaml programming language contains 3 components.
    • Target (Group)
    • Variable (Optional)
    • Tasks (Module)
  • Playbook language
---
 - hosts:  localhost # This is target
   tasks:
    - command: date
    - shell: cal
    - yum: name=httpd state=present
  • To check syntax error use this
ansible-playbook first.yaml --syntax-check
  • To run the playbook use the command
playbooks]# ansible-playbook first.yaml

---
 - hosts: a # This is target
   remote_user: ec2-user
   tasks:
    - command: date
    - shell: cal
    - yum: name=httpd state=present
  • To give a name or desciption specified for the command use - name
---
 - hosts: localhost # This is target
   tasks:
    - name: running date command
      command: date
    - name: install httpd software
      yum: name=httpd state=installed
  • To learn more about a module use this command
ansible-doc yum
  • You can also write your anible code like this, this is a new format.
---
 - hosts: localhost # This is target
   tasks:
    - name: running date command
      command: date
    - name: install httpd software
      yum:
       name=httpd
       state=installed
  • To know how many modules are there in ansible
ansible-doc -l
  • To count number of packages just by number you can use pipe and wc
ansible-doc -l | wc -l

Python Class

  • Functions are used to reuse code.
  • To create a function we use the keyword def
  • To call a function we write the function name with ()
  • For more information about functions click here

Ansible

  • create 2 instances
  • on 2nd instance crate a user passwd and
  • set the password authentication enable
  • on one instances ansible should be installed
  • ssh ec2-user@ip-of-2-instance any-command
$ ansible a -u ec2-user -m ping -k
asks for a password of os 2

$ ansible a -u ec2-user -m command "date" -k

$ ansible localhost -m command "date" -k
run command in your own system

$ ansible localhost -m shell -a "cal | wc -l"
 -a stands for argument
  • Idempotency - > whenever you ask a module to some work, ask the module to check the other OS if the same work is already done over there or not, if its done already then skip the task
  • Idempotency is done using yum module as
ansible localhost -m yum -a "name=software-name state=present"
  • to start service of any package
ansible localhost -m service -a "name=software-name state=started"
  • to copy a file from one place to another
ansible localhost -m copy -a "src=index.html dest=/var/www/html"
  • ansible not only checks for file name but for content inside it as well
  • ansible adhoc command - > running single command or using single module at a time to do some specific task
  • Playbook - > file containing all the ansible commands to be run for the completion of tasks
  • Playbook is wriiten in "YAML" - yet another markup language

Playbook ( language of YAML)

  • it has 3 parts
    1. Target - (group)
    2. Variable - (optional)
    3. Tasks - (module)
  • starts with ---
  • learn about syntax from below 
    - name: install the latest version of Apache
  yum:
    name: httpd
    state: latest
  • to check for syntac of play-book run command
$ ansible-playbook file.yml --syntax-check
  • to run a Playbook
$ ansible-playbook file-name.yml
  • to check for avavilable options for any module in ansible, run command
$ ansible-doc module-name
  • to send text message
debug:
 msg="any text message can be written here inside playbook"
  • list of all modules inside ansible
ansible-doc -l
  • Converting text into bytes is encoding

Man in the middle attack

  • arpspoof to be continued

Modules in Python

  • build using classes and functions

Functions

* these are of 2 types:
  1. with name
  2. without name
  • to insert input with file name
    1. import sys
    2. sys.argv - > filename var1 var2
    3. gives an list of everything written after python