What is Docker and Containers?

RajeshKumar1

Can you please answer the following questions

What is Docker?

What is Container?

What are the docker Components?

What is Docker Workflow?

What is Container Lifecycle?

How Container is powered by Kernel?

List of 15 Docker commands to explorere the Containers

ArunSolairajan

RajeshKumar1

What is Docker?
Docker simplifies the process of deploying, running and managing the applications which improves quality, maintenance and cost cutting.
What is Container?
Container is a image which consist of all the required tools, software required to run/deploy/maintain the application. It also helps to share CPU, memory, storage and network interface at OS level which helps to have multiple isolated setups.
What are the docker Components?
Docker hub
Docker client
Docker Daemon
Docker image
Docker container
What is Docker Workflow?
Docker workflow explain the process of building and deploying the application by creating as docker image.

Docker file
Docker image
Deploying the image
What is Container Lifecycle?
Create -> Run -> stop -> rm
Run -> pause -> unpause

How Container is powered by Kernel?
Container is powered by Kernel using namespace

PID
User
Mount
Network
List of 15 Docker commands to explorer the Containers
docker ps
docker pa -a
docker create httpd (creates httpd container)
docker create --name sas3 httpd (create httpd container with custom name sas3)
docker start container id
docker stop container id
docker restart container id
docker pause container id
docker unpause container id
docker kill container id
docker rm container id
docker inspect container id
docker exec -it container id command
docker inspect container id | grep -i "keyword"
docker pull image name

SantoshKumar

Docker is run time engine that provides all the commands to create container and manages them.
Containers are runtime environments that sits on the top of kernel to provide isolated runtime environment.

KhushiSinghania

What is Docker?
Docker is a tool that helps developers package applications and their dependencies into containers, making them easy to run on any system.

What is Container?
A container is a lightweight, isolated environment that runs an application with everything it needs (code, libraries, configs). It's like a mini virtual machine but faster and uses less space.

What are the docker Components?
Docker Engine
Docker CLI
Docker Images
Docker Containers
Docker Registry

What is Docker Workflow?
Write a Docker file, Build an image from it, Run a container from the image, Test or deploy the container, Push to Docker Hub

What is Container Lifecycle?
Create: Container is defined but not running.
Start: Container starts running.
Pause: Temporarily stop processes.
Stop: Gracefully stop.
Kill: Force stop.
Restart: Stop and start again.
Remove: Delete the container.

How Container is powered by Kernel?

Containers use the host OS kernel and features like namespaces and cgroups . This makes them fast and efficient, unlike full VMs that need their own OS

List of 15 Docker commands to explorere the Containers
docker version
which docker
which dockerd
which containerd
ps -eaf
lear
clear
docker info
ls
docker ps
docker ps -a
docker images
docker pull httpd
docker create httpd
docker create --name khush httpd
docker start 9b294ab57cba
docker restart 05f6c329193b
docker pause 05f6c329193b
docker unpause 05f6c329193b

SantoshKumar

Docker components are:-
Client - These provides APIs to connect docker runtime
Docker Engine
Docker Repo

SantoshKumar

Docker Workflow
Docker Client API requests for Docker Images through Docker Images, That is provided by Docker Registry and docker engine creates container based on the imgage

RifaquatullahKhan

What is Docker?
Docker is a container platform to containerize application.
What is Container?
In Docker container is light weight instance of image of application software.
What are the docker Components?
Image, Registry, Docker Daemon, Network etc
What is Docker Workflow?
Workflow is steps taken to run container application. It includes building and creating image of application and then creating container from image by downloading from docker repository
What is Container Lifecycle?
Lifecycle is stages through which Docker container goes through. states are Created, running, paused, stop and delete
How Container is powered by Kernel?
Kernel provides different namespaces for networking, storage, process management etc
List of 15 Docker commands to explorere the Containers
docker info
docker ps -a
docker images
docker pull
docker create
docker create --name khan httpd
docker start khan
docker pause khan
docker inspect khan
docker kill khan
docker stop khan

Kumar

What is Docker?
--> Docker is an engine, which manages Containers.
What is Container?
--> Light Weight Application Run Time Environment
What are the docker Components?
--> Clinet(CLI, API), Server, Registry
What is Docker Workflow?

Pulling Image from Registry
Preparing Container
Deploying it
What is Container Lifecycle?
Created, Running, Paused, Stopped, Deleted
How Container is powered by Kernel?
List of 15 Docker commands to explorere the Containers
docker version
docker info
docker pull
docker create
docker rm
docker stop
docker pause
docker unpause
docker kill
docker ps
docker ps -a
docker start
docker restart
docker images
15.

ManuBhatnagar

What is Docker?
Its a platform for containerzation. its helps to build lightweight application and package all the dependecies for a given app to run. It shares a common kernal host among other containers makes it quick n fast to build an deploy.

What is Container?
Containers helps to package all the required packaged software needed t run an application. Its an isolated unit works along with other containers. unlike VM it shares the common kernal for its functioning.

What are the docker Components?
Docker engine, ldockerD, Docker API, Docker cli, Docket Registry, docker network

What is Docker Workflow?
Docker helps to build containerzed environement. Helps to build, dploy, monitor and running the containerzied evnv. includes creating of image, pause, stop, start, remove jusing docker tool and commands etc.

What is Container Lifecycle?
it starts from creating the container, configuring it, running , mapping, stop, pause, restart etc till its termination.

How Container is powered by Kernel?
when a container is created , it coonects to kernal in order to create a isolated env, by gettng its own PID, user, MNT etc

ist of 15 Docker commands to explorere the Containers
docker version
docker create --name ubuntu-cont ubuntu
docker ps -a
docker pause <id>
docker restart <id>
docker stop <id>
docker rm <id>
docker info
docker unpause <id>
docker kill <id>

etc

TanujSharma

What is Docker?
Docker can be understood as a platform that enables isolation from host so that guest (containers) can be managed more efficiently as guest has its own separate world of process stack, mount points, networking, et cetera

What is Container?
Container can be understood as box which contains an image / object and provides isolation from host, can be moved, irrespective of base / host

What are the docker Components?

Engine, 2. Images, 3. Containers, 4. Registries

What is Docker Workflow?
Docker workflow is a process that includes 1. development, 2. packaging it (creating container), 3. putting it on server so that it can be pulled as per end user's requirement, 4. running or starting packaged object / image

What is Container Lifecycle?
Create -> Run -> Pause (if required) -> Stop -> Removal/deletion

How is container powered by Kernel?
Container engine secures namespaces from host kernel as it does not have it's own kernel

List of 15+ Docker commands to explorer the Containers

which docker - to tell which client is installed
which dockerd - to tell which server is installed
docker info - detailed info about docker
docker ps - tells about running containers
docker ps -a - tells about all containers, irrespective of their state
docker images - tells about list of all local images that can be installed on local host
docker pull <image_name> - pulls/installs image (eg, httpd, nginx, et cetera)
docker create --name <image_name> - create container
docker start <container_id|name> - starts installed container
docker stop <container_id|name> - stops installed container
docker restart <container_id|name> - restart installed container
docker pause <container_id|name> - pause installed container
docker unpause <container_id|name> - unpause installed container
docker kill <container_id|name> - unpause installed container
docker rm <container_id|name> - remove/delete installed container
docker exec -it <container_id|name> /bin/bash - login to the container
docker inspect <container_id|name> - detailed info about the container

pankajsharma

What is Docker?
Docker is run time engine that sit above the kernel like hypervisor in VM and it provide the runtim environment for containers
What is Container?
Containers are light weight application runtime without the kernel. Container is image with user,PID,NET,MNT attached to it
What are the docker Components?
Docker Client ,Docker daeomon,Docker server,Registry hub

What is Docker Workflow?

What is Container Lifecycle?
create,deploy,start,stop,pause kill

How Container is powered by Kernel?

List of 15 Docker commands to explorere the Containers
docker ps -a

docker exec -it conatinername
docker ps
docker start containername
docker pause conatinername
docker inspect containername
docker pull httpd
docker stop conatinername
docker images
sudo apt install procps
sudo
ls
ps -eaf
pwd

SantoshKumar

Container Life Cycle
Contaoner Created=> Container Started=>Container Paused/Unpaused=>Container Killed/Stop=> Container Delete

How container is powered by Kerner?
Kernel is the root which takes all the commands from all of the containers. Hence, kernel usablility increases, whereas container itself becomes light weight,

Commands:-
docker version
which docker
which containerd
which dockerd
docker info
docker images
docker create httpd
docker create imagename
docker start conainerid/name
docker stop containername/id
docker stats
docker pause containername/id
docker unpause containername/id
dicker kill containername/id
docker stop containername/id
docker inspect

likithadonta

What is Docker?
A container Management platform, light weight tool for containerzation [manager defentiation]

What is Container?
A lightweight isolated environment to run the applications more efficiently and without wasting time and resoucres.

What are the docker Components?
Dcoker Engine, docker cli, docker image, docker container, docker daemon, registry, server host.

What is Docker Workflow?
A user will make a command to client will go server and check, then the server will check registry [ docker hub]

What is Container Lifecycle?
Created, Running, Paused, Stopped, Deleted [ Commands to do it - create, start, run, pause,stop, rm ]

How Container is powered by Kernel?
Kernel powers containers by
namespaces- (pid, user, mount, net)
cgroups
capabilities
Selinux
kernel gives the container it's own isolated user file system and root file system.

List of 15 Docker commands to explorere the Containers
[commands learned on day 1]
docker images
docker create
docker ps
docker ps -a
docker run -itd --name ubuntu-cont ubuntu
docker start
docker stop
docker restart
docker inspect
docker kill
docker rm cont1 cont2 cont3
docker pull
docker unpause

RajaS

What is Docker?
Docker is a container management platform which allows us build, run & manage containers. Helps us to handle the complete container lifecycle starting from development to deployment
What is Container?
Container is a bundle or package of softwares with required dependencies to host our application. Containers can be created using base images from in Docker registeries, which holds millions of images globally and gives ability to chose the Verified images.
What are the docker Components?
Below are the key components in docker

Docker engine - responsible for building, managing & running the containers
Docker images- can be used to create containers with pre-defined setup. For e.g. with httpd image, we can create container holding Apache Web server
Docker containers - Bundles / package of softwares with required dependencies
Docker registries - holds different images
Docker hub - platform to explore images in registeries

What is Docker Workflow?
Develop application & create docker file -> Create / host images to hub -> Create container -> start container / app -> deploy
What is Container Lifecycle?
Create -> Start -> pause -> unpause -> stop -> rm
run -> pause -> unpause -> stop -> rm
How Container is powered by Kernel?
Containers doesnt rely separate / dedicated OS, instead relies on the Kernel of host's OS. Containers isolates the processes by using namespaces (user, pid, network, mount) and control groups (cgroups)
List of 15 Docker commands to explore the Containers

docker ps -a
docker images
docker pull imagename
docker create --name contwithname httpd
docker create --name contwithport -p 8080:80 httpd
docker start containerid
docker stop containerid
docker pause containerid
docker unpause containerid
docker rm containerid
docker restart
docker run -it --name contwithrun
docker inspect -- I used to find the IP of container
docker exec containerid /bin/bash
docker exec
docker inspect

durgaA

What is Docker? docker provides containers managed platform tools. Docker is mainly to save cost, time and improve the quantity. Docker uses containerd to access the kernel

What is Container? Containers is created for isolation process each with unique PID, USER, Mount, net mapped for a user
What are the docker Components?

Docker Engine Docker engine will create image
Images will help to create containers
containers containers is created for isolation process
Registry contains version filesystem

What is Container Lifecycle? - Create - Running - paused - Running - stopped - Delete

Commands
docker version
docker ps -a
docker ps
which docker
which containerd
docker exec -it --name /bin/bash
docker start --name
docker stop --name
docker restart --name
docker info
clear
ps -efa
docker pause --name
docker pull httpd
docker create httpd

How Container is powered by Kernel? Containers will interact with kernel with the help of containerd. It uses the features of Kernel - Namespace(pid, mount, net, user), Cgroup, capabilities, SELinux, With these features containers will create isolated process

Docker workflow - create the docker image/pull the image form Dockerhub - docker image will create the container

RamEsh

What is Docker
Docker is a container management platform which allows us build, run & manage containers. Helps us to handle the complete container lifecycle starting from development to deployment
What is Container
A lightweight isolated environment to run the applications more efficiently and without wasting time and resoucres.
Commands:-
docker version
which docker
which containerd
which dockerd
docker info
docker images
docker create httpd
docker create --name imagename
docker start conainerid/name
docker stop containername/id
docker stats
docker pause containername/id
docker unpause containername/id
dicker kill containername/id
docker stop containername/id
docker inspect

What is Container Lifecycle?
Create -> Start -> pause -> unpause -> stop/kill -> rm

What are the docker Components?
Docker Engine, docker cli, docker image, docker container, docker daemon, registry, server host.

DivyaPriya

Q1. What is Docker?

Docker is a control Management Platform/Tool.
Tool is used for saving cost, saving time and improve quality.
Using Docker we can create, start, run, pause, delete and stop the container.
It is a platform which allows us to build to manage the applications in lightweight, portable containers.

History of Docker:

Docker is actually name of the company - we have so many products in it like dotCloud, etc.
The first product of Docker is a Docker engine.

Why we change the Tool:

To save cost, save time and improve the quality. Same applies to when to migrated from Virtual to Docker.

Need of Docker:

It is Isolation: each applications runs its own Container without any conflicts.
It is Consistent: Can works on the same Dev, Test and Production environments.
It is Portable: Can run anywhere, on Cloud or Server or PC.
It is Efficient: Uses less Memory & storage than Virtual Machines.

Concepts of Docker:

Docker images: It is a template or blueprint.
Docker container: A running instance of an image.
Docker file: A script which defines how to build a Docker Image.
Docker hub: A public registry for sharing Docker images (Like GitHub).
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Q2. What is Container?
Container is an actual product/outcome of the tool.
Containers are light-weight than Virtual Machines.
In Virtual Machine, has its own full Operating System. Whereas in Container shares the Operating System kernel.
In Virtual Machine, shares more RAM & CPU. Whereas in Container it is minimal resources.
In Virtual Machine, occupies more Memory. Whereas in Container it is less.

History of Container:

Containers aren't a new technology, they have been around for decades. Docker made them easy, portable and developer friendly.

Life cycle of Docker Container:

To create, start, run, pause, delete and stop are the process involves in Docker Container cycle.
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Q3. What are Docker Components?

Docker Components:
A. Docker image,
B. Docker container,
C. Docker engine,
D. Docker file,
E. Docker hub or registry,
F. Docker network, and
G. Docker volume

A. Docker Image

Read-only blueprint which used to create containers.
Which creates the Container: (Ex: 1 Root File System, 1 User File System, Application File System)
- Root file system can be Linux, Windows OS, etc.
- User file system can be User1, User 2, etc.
- Application file system can be Apache, Notepad, etc.

B. Docker Container

A running instance of Docker Image.

C. Docker Engine

Docker Engine is Software, PC, Client, and Server that can run wherever everywhere we can.
The client-server communication that executes the Docker.
It has 2 parts:
- Docker Daemon (which runs in the background and manages images, containers, etc).
- Docker CLI (which is the Command-line tool to interact with Docker.

D. Docker File

A script which contains the instructions to build a Docker image.

E. Docker Hub

A cloud-based registry used to store and share the Docker Images.
Docker hub is a registry, which has Docker image = 1 Root File System +1 User File System

F. Docker Volume

Which is Consistent, persistent storage mechanism for Containers.

G. Docker Network

Which enables the communication between containers and external systems.
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Q4. What is Docker Workflow?

A. Docker to Container

A lightweight runtime environment and the solution is Containers.
Implies to creates or configures the container using Docker tools.

B. Client-Server Docker Architecture

User run a Docker command (Ex: Docker run).
Hits the Docker Client, which talks to the Docker Daemon (dockerd) a Server.
dockerd checks if the image is available locally.
If not found, pulls from Docker Hub.

C. Docker Daemon to Container Runtime (dockerd ----> containerd ---> kernel)

dockerd: Main docker server process.
containerd: Lightweight container runtime that manages container lifecycle.
Communicates with the kernel to create Namespaces and control groups.

D. Namespaces and Isolation

When container is created, Docker uses Namespace to isolate it.
- USER ---> User access inside container
- NET ---> Network stack (container gets its own virtual network)
- PID ---> Process IDs inside the container
- MNT --> Filesystem mount points (container sees only its own file system)

E. Container Construction

These namespaces and isolated environments are attached to as user process, forming a container.
One container = an isolated instance with its own processes, network, and filesystems.

Workflow Preview:

User ---> Docker CLI ---> Docker Daemon (dockerd)
---> Image lookup (local or pull from Docker Hub)
---> containerd runs container
--->Two types of Kernels (Based on Host OS - Linux, Windows)
* We should not compromise stability and security of Kernel and User space while they communicate
* Kernel must not be compromised to ensure container isolation
---> Kernel creates namespaces (USER, NET, PID, MNT)

---> All together to user process = 1 Container (Fully isolated)

Q5. What is Container Lifecycle?

Container Lifecycle:
A. Create
B. Start
C. Pause
D. Unpause
E. Stop
F. Kill
G. Restart
F. Delete or Remove

A. Create or Run

Container is created from image but not running yet.

B. Start

Starts a new or stopped created container.

C. Pause

Temporarily suspends processes inside the container. But container exists.

D. Unpause

Resumes a paused container.

E. Stop

Stops a running container. Container remains on disk.

F. Kill

Forcefully stops the container immediately.

G. Restart

Stops and then starts the container again

I. Remove or Delete

Deletes the container completely. And it cannot be restarted again.
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Q6. How is Container powered by Kernel?

A. Kernel is the core part of OS, it controls CPU, Memory, other resources.
B. Containers don't have their own OS, they share the host machine's kernel.
C. While running a container, Docker asks the Kernel to:
* Run the application in a separate space (Namespace).
* Limit he resources (cgroups).
* Keep it isolation from other containers.
D. Kernel creates a Safe, isolated area for the container.
E. Container runs like a normal program.
* It cannot see or affect other application functionalities.
* It imagines its running on its own system.

F. Thats the reason why containers are fast, and lightweight, especially they don't require their own OS.

Q.7 List of 15 Docker commands to explorere the Containers

A. To install Docker engine in Ubuntu

sudo -s (sudo is to run a command as a superuser, -s is to start a shell with root privileges)
Install the Docker engine, if its installed work on the Docker Containers commands.

B. Docker commands to explorer the Containers

docker images (to view the docker images)
docker pull httpd (to pull an image from docker hub or another container registry)
docker create httpd (creates an image)
docker ps -a (to list all container including running, stopped, exited on the machine)
docker ps (to list the currently running containers on the machine)
docker run -itd --name new_httpd httpd (to create a container, the image httpd here were the preferred namespace we can have any name instead of new_httpd, also it creates with ports like 80/tcp)
docker start f08679d02d97 (starts the container, f08679d02d97 is a container ID)
docker pause f08679d02d97 (pause the container, f08679d02d97 is a container ID)
docker unpause f08679d02d97 (unpause the container, f08679d02d97 is a container ID)
docker container ls (to list all the running container)
docker image ls (to list docker images)
docker kill f08679d02d97 (forcefully kill the container, f08679d02d97 is a container ID)
docker restart f08679d02d97 (restart the container, f08679d02d97 is a container ID)
docker stop f08679d02d97 (stop the container, f08679d02d97 is a container ID)
docker rm f08679d02d97 (remove all container, f08679d02d97 is a container ID)
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VaibhavBansal

What is Docker?
Docker is an open-source platform that automates the deployment and management of applications inside containers. It packages software along with its dependencies and environment settings, ensuring consistent behavior across different systems.
What is a Container?
A container is a lightweight, isolated execution environment that includes an application and everything it needs to run. It shares the host OS kernel but operates independently, making it fast and resource-efficient.
What are the Docker Components?

Docker Engine: Core runtime for building and managing containers.

Docker CLI: Command-line tool to interact with Docker.

Docker Images: Templates used to create containers.

Docker Containers: Running instances of images.

Dockerfile: Instructions to build Docker images.

Docker Hub: Cloud-based registry for sharing images.

Docker Compose: Tool for running multi-container apps.

Docker Daemon: Background service managing containers/images.

What is Docker Workflow?

Write a Dockerfile

Build the image (docker build)

Run a container (docker run)

Test and debug

Push to registry (e.g., Docker Hub)

Deploy to other environments

What is Container Lifecycle?

Created: Container defined but not running.

Running: Container is executing.

Paused: Execution temporarily suspended.

Stopped: Execution halted.

Restarted: Started again after stop/failure.

Removed: Container deleted from system.

How Container is Powered by Kernel?
Containers use kernel features like:

Namespaces: Isolate system views (PID, network, mounts, etc.)

Cgroups: Control resource usage (CPU, memory, disk I/O)
These features allow containers to run isolated processes using the host OS kernel without needing a full OS per container.

15 Docker Commands to Explore Containers:

docker --version → Check Docker version

docker ps → List running containers

docker ps -a → List all containers

docker images → List images

docker pull <image> → Download image

docker run <image> → Run container

docker run -it <image> /bin/bash → Interactive shell

docker exec -it <container_id> /bin/bash → Run command in container

docker logs <container_id> → View logs

docker inspect <container_id> → Container details

docker stop <container_id> → Stop container

docker start <container_id> → Start container

docker restart <container_id> → Restart container

docker rm <container_id> → Remove container

docker stats → Live resource usage

prasadchaudhari

What is Docker?
Docker is a container platform to containerize application.
What is Container?
In Docker container is light weight instance of image of application software.
What are the docker Components?
Image, Registry, Docker Daemon, Network etc
What is Docker Workflow?
Workflow is steps taken to run container application. It includes building and creating image of application and then creating container from image by downloading from docker repository
What is Container Lifecycle?
Lifecycle is stages through which Docker container goes through. states are Created, running, paused, stop and delete
How Container is powered by Kernel?
Kernel provides different namespaces for networking, storage, process management etc
List of 15 Docker commands to explorere the Containers
docker info
docker ps -a
docker images
docker pull
docker create
docker create --name Test httpd
docker start Test
docker pause test
docker inspect Test
docker kill Test
docker stop Test

SanyaGarg

What is Docker?
Docker is a container management platform/tool that uses OS-level virtualization to deliver software in packages called containers.

What is Container?
A container is a lightweight, executable package providing an isolated environment to run an application and its dependencies.

What are the docker Components?

Docker Engine
Registries and Repositories
Docker Images
Containers

What is Docker Workflow?
Docker Workflow refers to the process of developing, building, and deploying applications using Docker. It involves the following steps:

User sends a request to docker client
Docker clients requests docker server(Docker Daemon)
It checks if docker image exists in local
If not found, downloads image from docker hub to local
DockerD sends image to containerD
ContainerD accesses the kernel to create USER, NET, PID, MNT
Attach this USER to PID, NET, MNT to create a container

What is Container Lifecycle?

Created: container that has been created but not started
Running: container running with all its processes
Paused: container whose processes have been paused
Stopped: container whose processes have been stopped
Deleted: container in a dead state

How Container is powered by Kernel?
Containers rely on the host operating system's Linux kernel for their functionality, specifically through features like namespaces and control groups (cgroups). Instead of each container having its own kernel, they share the host's kernel, making them lightweight and efficient.

List of 15 Docker commands to explorere the Containers?
docker version
which docker
which dockerd
which containerd
ps -eaf
lear
clear
docker info
ls
docker ps
docker ps -a
docker images
docker pull httpd
docker create httpd
docker create --name <container name> httpd
docker start <container id>
docker restart <container id>
docker pause <container id>
docker unpause <container id>