Lecture Notes

Server Setup and Configuration

Initial Server Setup

• Master node is on AWS, using Red Hat.
• Node one is Ubuntu.
• Node two is Red Hat (CentOS/Linux).

Master Node Configuration

• Set the hostname:
  • sudo hostnamectl set-hostname master
  • Update the system: sudo apt update.

User Creation

• Create a new user:
  • sudo useradd asadmin
  • Set the password: sudo passwd asadmin
  • Add the user to the sudoers file (sudo visudo):
    • Add the line: asadmin ALL=(ALL:ALL) ALL

SSH Configuration

• Enable password authentication in SSH:
  • Edit the SSH configuration file: sudo vi /etc/ssh/sshd_config
  • Uncomment PasswordAuthentication yes
  • Add/modify PermitEmptyPasswords no.
  • Add/modify Copy this line with the cloud in it, paste it, and say yes.
• Restart SSH service:
  • sudo service sshd restart (old version) or sudo systemctl restart sshd

Worker Node One (Ubuntu) Configuration

• Create a user:
  • sudo adduser asadmin
  • Set the password.
  • Add user to sudoers: sudo vi /etc/sudoers
    • Add the line: asadmin ALL=(ALL:ALL) ALL
• Configure SSH:
  • sudo vi /etc/ssh/sshd_config
    • Enable password authentication: PasswordAuthentication yes
  • Modify cloud init: sudo vi /etc/cloud/cloud.cfg.d/99-disable-password-auth.cfg
    • Change ssh_pwauth: no to ssh_pwauth: yes
• Restart SSH: sudo systemctl restart ssh

Worker Node Two (Red Hat/CentOS) Configuration

• Set hostname:
  • sudo hostnamectl set-hostname node1
  • sudo hostnamectl set-hostname node2
• Create user:
  • sudo useradd asadmin
  • sudo passwd asadmin
• Add user to sudoers: sudo vi /etc/sudoers
  * Add the line: asadmin ALL=(ALL:ALL) ALL
• Configure SSH:
  • sudo vi /etc/ssh/sshd_config
    • Enable password authentication: PasswordAuthentication yes
  • Modify cloud init: sudo vi /etc/cloud/cloud.cfg.d/99-disable-password-auth.cfg
    • Change ssh_pwauth: no to ssh_pwauth: yes
• Restart SSH: sudo systemctl restart sshd

Testing SSH Access

• Log in as the new user:
  • sudo su - asadmin
• SSH from master to worker nodes:
  • ssh asadmin@<public_ip>

SSH Key Generation and Distribution

• Generate SSH key on the master node:
  • ssh-keygen
• Copy the public key to worker nodes:
  • ssh-copy-id asadmin@<worker_node_public_ip>

Ansible Installation and Configuration

• Install pip:
  • sudo apt install python3-pip (Ubuntu)
• Install Ansible:
  • pip3 install ansible==2.15.13
• Verify Ansible installation:
  • ansible --version

Ansible Project Setup

• Create a project directory:
  • mkdir projects
  • cd projects
• Create an inventory file (inventory):
  • Define groups (dev, qa) with server IP addresses.
• Create an Ansible configuration file (ansible.cfg):
  • ini [defaults] inventory = ./inventory host_key_checking = False
• Set environment variables:
  • export ANSIBLE_HOST_KEY_CHECKING=False

Testing Ansible Setup

• Ping the dev environment:
  • ansible dev -m ping
• Ping the qa environment:
  • ansible qa -m ping
• Ping all servers:
  • ansible all -m ping

Ansible Modules

• Command Module: Executes shell commands.
• Shell Module: Executes shell commands (more powerful than command module).
• File Module: Manages files and directories.
• YUM Module: Installs, updates, and removes packages on Red Hat-based systems.
• Setup Module: Gathers facts about the managed hosts.

Gathering Facts

• Use the setup module to gather information about the servers.
  • ansible all -m setup
• Filter facts to get specific information:
  • `ansible dev -m setup -a