DevOps Interview Questions

Table of Contents

1. Jenkins
2. AWS
3. Network 4. Linux

Jenkins

beginner

• Explain what is Jenkins and what is it used for
• Explain each of the following in the context of nodes:
  • Master
  • Slave
  • Executor
  • Agent
  • Label
• Explain each of the following in context of jobs:
  • Job
  • Build
  • Test
  • Artifacts
• Explain the architecture of Jenkins
• What are the different ways to trigger a build?
• How do you start a build automatically upon a change in a certain repository?
• What is a plugin?
  • What plugins are you using in Jenkins? Which do you consider to most useful?
• Installation questions
  • How to install Jenkins?
  • How to install a plugin?
  • How to install an agent?

Intermediate

• What type of jobs there are?
• How do you notify users on build results?
  • Can also be asked like that: what ways there are to notify users on build results?

Advanced

• Write a script to remove all the jobs which include the string "REMOVE_ME"

AWS

Global Infrastructure

• Explain the following
  • Availability zone
  • Region
  • Edge location

S3 - beginner questions

• Explain what is S3 and what is it used for
• What is a bucket?
• True or False? a bucket name must be globally unique
• What objects in S3 consists of?
  • Another way to ask it: explain key, value, version id and metadata in context of objects
• Explain data consistency
• Can you host dynamic websites on s3? what about static websites?

CloudFront

• Explain what is CloudFront and what is it used for
• Explain the following
  • Origin
  • Edge location
  • Distribution
• What delivery methods available for the user with CDN?
• True or False? object are cached for the life of TTL

Network

Network questions can be found here

Linux

• What is the different between a soft link and hard link?

hard link is the same file, using the same inode.
soft link is a shortcut to another file, using a different inode.

soft links can be created between different file systems while
hard link can be created only within the same file system.

• How to run a process in background and why to do that in the first place?

You can achieve that by specifying & at end of the command.
As to Why? since some commands/processes can take a lot of time to finish
execution or run forever

• What signal is used when you run 'kill '?

The default signal is SIGTERM (15). This signal kills
process gracefully which means it allows it to save current
state configuration.
followup questions:
what is SIGKILL?
what other signals there are?

Ansible

• Describe each of the following components in Ansible, including the relationship between them:
  • Task
  • Module
  • Play
  • Playbook
  • Role

Task – a call to a specific Ansible module
Module – the actual unit of code executed by Ansible on your own host or a remote host. Modules are indexed by category (database, file, network, …) and also referred as task plugins.

Play – One or more tasks executed on a given host(s)

Playbook – One or more plays. Each play can be executed on the same or different hosts

Role – Ansible roles allows you to group resources based on certain functionality/service such that they can be easily reused. In a role, you have directories for variables, defaults, files, templates, handlers, tasks, and metadata. You can then use the role by simply specifying it in your playbook.

• Write a task to create the directory ‘/tmp/new_directory’

- name: Create a new directory
  file:
      path: "/tmp/new_directory"
      state: directory

• What would be the result of the following play?

---
- name: Print information about my host
  hosts: localhost
  gather_facts: 'no'                                                                                                                                                                           
  tasks:
      - name: Print hostname
        debug:
            msg: "It's me, {{ ansible_hostname }}"

When given a written code, always inspect it thoroughly. If your answer is “this will fail” then you are right. We are using a fact (ansible_hostname), which is a gathered piece of information from the host we are running on. But in this case, we disabled facts gathering (gather_facts: no) so the variable would be undefined which will result in failure.

• Write a playbook to install ‘zlib’ and ‘vim’ on all hosts if the file ‘/tmp/mario’ exists on the system.

---
- hosts: all
  vars:
      mario_file: /tmp/mario
      package_list:
          - 'zlib' 
          - 'vim'
  tasks:
      - name: Check for mario file
        stat:
            path: "{{ mario_file }}"
        register: mario_f

      - name: Install zlib and vim if mario file exists
        become: "yes"
        package:
            name: "{{ item }}"
            state: present
        with_items: "{{ package_list }}"
        when: mario_f.stat.exists

• Write a playbook to deploy the file ‘/tmp/system_info’ on all hosts except for controllers group, with the following content

  I'm <HOSTNAME> and my operating system is <OS>
  

  replace and with the actual data for the specific host you are running on

The playbook to deploy the system_info file

--- 
- name: Deploy /tmp/system_info file
  hosts: all:!controllers
  tasks: 
      - name: Deploy /tmp/system_info
        template:
            src: system_info.j2 
            dest: /tmp/system_info

The content of the system_info.j2 template

# {{ ansible_managed }}
I'm {{ ansible_hostname }} and my operating system is {{ ansible_distribution }