Docker Interview Question & Answer In 2025

Who Developed Docker?

Soloman hykes, Wriiten in Golang

  1. What is docker??

It is container based technology and it is help to mange containers

2 . Why do we use this tool?

using a tool, we save time, save cost, Improve quality and Effienecy

3. Where save time, save cost, Improve quality and Effiency ?

To run Apps (Data Center)

  1. What is container??

A Docker container is a lightweight, isolated environment that runs applications. It contains all the components needed to run an application, including the code, dependencies, and libraries.

5. what are the resources needed for the running a App?

Hardware -> OS

Kernal Types


CGroup — Allocated CPU + RAM to process using PID


6 .Who can decide its root or not root

Ans . In security, capability will be decide by

7. what is Mount?

C-drive, d-drive is a mount

8 What we need ??

  1. Hardware
  2. Operating System
  3. Mount (Filesystem)
  4. App

9. What is PID?

PID stands for Process IDentifier

Zero -> (0) Is super Orgin for Everything

10. What is Linux?

Linux is an open-source operating system (OS). An operating system is software that directly manages a system’s hardware and resources, like CPU, memory, and storage. The OS sits between applications and hardware and makes the connections between all of your software and the physical resources that do the work.

11. What are Linux OS Flavors?

Popular Linux distros

Android.
Arch Linux.
Centos.
Debian.
Elementary OS.
Fedora Linux.
Gentoo Linux.
Kali Linux.

12. What is Kernel?

hardware–> kernel
kernel is important for all the OS.
The kernel is a computer program.

The Linux kernel enables the communication between hardware and software via drivers included in the kernel or added via kernel modules. It is also in charge of managing the system’s resources, including as memory management, process and task management, and disc management.
(it is talking to hardware and human layers).

13. What is virtual box?

It is hypervisor, managing vms(virtual Machine system).

14. What is filesystem?

collection of files/directly for certain purpose.

Types of Filesystem

boot filesystem —–This is a Kernel
root filesystem —— what you see… war, etc, linux opt only two kernel available in world (window kernel and Linux kernel system)
user filesystem —— c:\users\Roshan Kumar> start .(dot)

15. What is absolute path and relative path?

Absolute path ====> start from the root.
Relative Path ====> start from current directory.

16. What is VM?

It is hypervisor on the top of base kernel. It contains( boot filesystem, root filesystem, user filesystem, App filesystem) in form of image .
Then, It creates one instance (virtual machine) and many more virtual machine. It sends in the form of an image what you have in the image to one instance (virtual machine) and many more instances (virtual machine) where image goes through kernel{This is not base kernel}, then root, then user, then application).
They behave like independently but it not independent all are control by base kernal and hardware.

17. Why we need docker??

In 2021 , we can’t afford the virtualization technology we can’t use multiple os so we avoid cpu,ram,storage,liences cost

18. What is Load Balance??

At a time one apache will be load not multiple apache means at a time one port will be load like at a time 80 port will be load not 81 or 82 port will be load and runn.

An operating system contains

Boot–>root–>user–>App

Container contains

Root–>user–>App

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