RHCE_ENV

An environment made as a preparation for RHCE [EX294] exam

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Useful tips:

1- Gather facts again inside the playbook

• Can be done using the setup module

- name: gather facts again
  setup:

• Can also be done using another play inside that playbook

hosts: localhost
tasks:
  - name: install httpd
    yum:
      name: httpd
      state: latest 

hosts: localhost # facts are being gathered again
tasks:
  - name: gather package facts
    package_facts:
      manager: auto

2- Edit ~/.vimrc to allow auto indent

vi ~/.vimrc
set ai

3- Add --syntax-check flag at the end of the command to verify there was no syntax issues, remove it quickly using ctrl + w

ansible-playbook <name>.yml --syntax-check

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rhel-system-roles:

sudo yum install -y rhel-system-roles

📁 Important dirs:

• /etc/ansible/

  • hosts
  • ansible.cfg
  • facts.d/ # for storing custom facts (file extension must be .fact)

• /usr/share

  • /ansible/roles
  • /doc/rhel-system-roles

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🕐 Fact caching:

• Mainly done when managing a large fleet of servers to save the time spent gathering facts at the beginning of the playbook.

1. Caching using redis

[defaults]
gathering = smart
fact_caching = redis
fact_caching_timeout = 7200 # 2 hours timeout

2. Caching locally using a file

[defaults]
gathering = smart
fact_caching = jsonfile
fact_caching_timeout = 7200
fact_caching_connection = /tmp/fact_cache

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Ansible Facts:

• ansible_local used to get local facts stored in /etc/ansible/facts.d/.fact

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Magic Variables:

1. hostvars # access vars defined for any host in the play
2. groups # List of all groups in the inventory
3. group_names # List of groups that the current host is part of
4. inventory_hostname # same as ansible_hostname
5. inventory_file

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Quick Tip for configure managed nodes objective:

1- Generate the ssh key on controller node first ssh-keygen 2- Make a shell script that automates the user creation, password and privilege escalation part 3- use scp to place it in /tmp on all the hosts that will be managed 4- run it then from controller copy ssh key using ssh-copy-id

useradd ansible 
echo ansible | passwd --stdin ansible 
usermod -aG wheel ansible 
echo "ansible ALL=(ALL) NOPASSWD: ALL" > /etc/sudoers.d/ansible

List of hosts that will be managed:

192.168.50.221 ansible1
192.168.50.222 ansible2
192.168.50.223 ansible3
192.168.50.224 ansible4

An easier approach for achieving same objective is to generate the keys then use group_vars and use the all group to set ansible_ssh_password to the host password then make a playbook that uses authorized_key module to place the generated ssh key to the managed hosts

- hosts: all
  tasks:
    - name: copy authorized keys
      authorized_key:
        user: vagrant
        key: "{{ lookup('file', '/home/vagrant/.ssh/id_rsa.pub') }}"