What is Docker:
Docker is an open source platform that helps developers to build, share, deploy and run modern applications. This platform uses OS level virtualization called containers, and the software that contains these containers is called the docker engine.
Docker can also be defined as a technology to package an application and all its dependencies into a single and easily transportable and isolated container. This container will run exactly in the same fashion, regardless of the computer it is run on. This technology has fixed the famous traditional “but it runs on my machine” problem. You can imagine your container as lightweight virtual machine in which all the dependencies of the application are present. Your computer can run multiple containers at the same time starting and stopping them individually as required.
Docker Image VS Docker Container:
Docker Image: A docker image is nothing but a set of instructions to build a docker container. It is a file use to execute the code in a docker container. Docker uses a Dockerfile to build images by reading instructions from it. A Dockerfile is a text document with all the instructions and commands a user will use to assemble the docker image.
Docker Container: Docker container is the run time instance of a docker image. The docker gets created as soon as the docker run image_name command is called. Here the image_name will be replaced with the name of the image you are using to create a container.
Docker Containers VS Virtual Machines:
Docker containers and virtual machines are two different approaches to creating isolated environments for running applications. While they both provide isolation and encapsulation, they differ in their architecture and resource usage.
Docker Containers:
A Docker container is a lightweight, standalone, and executable package that contains everything needed to run an application, including the application code, libraries, dependencies, and system tools. Docker containers run directly on the host operating system and share the kernel with other containers on the same host. This means that Docker containers are much more lightweight and efficient than virtual machines.
Docker containers are isolated from each other using namespaces and cgroups, which provide a secure environment for running applications. Each container has its own file system, networking, and process space, which means that applications running in one container cannot affect other containers on the same host.
Docker containers are created using Docker images, which are built using a Dockerfile. Docker images are created by layering file system changes on top of a base image. This makes it possible to share common components between images, which reduces the overall size of the images.
Virtual Machines:
A virtual machine (VM) is an emulated computer system that runs on top of a host operating system. A virtual machine includes its own operating system, application stack, and hardware emulation, which makes it a complete and isolated environment.
Virtual machines are created by running a hypervisor on the host operating system, which creates a virtualized environment for the guest operating system to run in. Each virtual machine has its own resources, including CPU, memory, and disk space, which are allocated by the hypervisor.
Virtual machines provide strong isolation and encapsulation, which makes them ideal for running applications that require a high degree of security and isolation. However, virtual machines are much less efficient than Docker containers, as they require a significant amount of resources to run.
Differences between Docker Containers and Virtual Machines:
- Resource Usage:
Docker containers are much more lightweight and efficient than virtual machines. Docker containers share the host operating system kernel, which means that they require much less memory and CPU resources than virtual machines.
Virtual machines, on the other hand, require a significant amount of resources to run, as they include their own operating system, application stack, and hardware emulation.
- Isolation:
Both Docker containers and virtual machines provide isolation and encapsulation. However, Docker containers are more lightweight and provide a lower level of isolation than virtual machines. Docker containers share the host operating system kernel, which means that there is a greater risk of one container affecting another container on the same host.
Virtual machines provide strong isolation and encapsulation, as each virtual machine includes its own operating system, application stack, and hardware emulation. This makes virtual machines ideal for running applications that require a high degree of security and isolation.
- Portability:
Docker containers are highly portable, as they can be easily moved between different host operating systems and platforms. Docker containers include everything needed to run an application, which means that there are no dependencies on the host operating system or hardware.
Virtual machines are less portable than Docker containers, as they include their own operating system and hardware emulation. This means that a virtual machine may not run on a different hypervisor or hardware platform without modification.
Conclusion:
In conclusion, Docker containers and virtual machines are two different approaches to creating isolated environments for running applications. While they both provide isolation and encapsulation, they differ in their architecture and resource usage. Docker containers are more lightweight and efficient than virtual machines, and are highly portable. Virtual machines provide strong isolation and encapsulation, and are ideal for running applications that require a high degree of security and isolation.