What is a Container
A container is a collection of one or more discrete processes, separated from the host system they run on.
The container’s operating system is in the form of an image. The difference between this and the host operating system is that the image only includes the file system and binaries for the OS, whereas the full OS includes the file system, binaries, and the kernel.
Containers are portable and consistent as they move from one emvironment to another, for example from development to testing to production. Because of this, they operate far more quickly than development pipelines that rely on simulating conventional testing environments. Containers are a crucial element of IT security due to their widespread use and simplicity.
Containers are lightweight and contain everything required to run an application, eliminating the need to rely on what is already installed on the host. You can easily share containers while working, and you can be sure that everyone with whom you share gets the same container that works in the same way.
Instead of emulating a full operating system, containers use the kernel of the host system on which they run. As a result, containers have direct access to host system resources.
Containers add speed and flexibility by isolating operating systems and applications from the rest of the system. They are portable, simple to duplicate, and transfer to different operating systems.
What is Docker
Docker is an open-source containerization platform that is used to develop, deploy, and manage applications in containers.
Docker encapsulates an application and all of its dependencies within a virtual container that can run on any server. Due to this, we refer to them as containers, because they just require one piece of software that contains all the required dependencies.
The idea may seem comparable to virtual machines because Docker uses virtualization to construct containers for storing software. There are significant distinctions between containers and virtual machines (VMs), despite the fact that both represent isolated virtual environments used for software development. The most significant contrast is that compared to virtual machines, Docker containers are lighter, faster, and more resource-efficient.
So why is Docker suddenly gaining popularity? Few reasons below:
- Very easy to use: Docker has made it much simpler for everyone to utilize containers in order to swiftly build and test portable applications, including developers, systems administrators, architects, and others.
- Speed: Docker containers are quick and incredibly light. Containers use fewer resources since they are merely sandboxed environments operating on the kernel. A Docker container can be created and run in a matter of seconds as opposed to a virtual machine (VM), which may take longer because it must start up a full virtual operating system each time.
- Docker Hub: The ever-expanding ecosystem of Docker Hub, which you can think of as a “app store for Docker images,” is beneficial to Docker users as well. Tens of thousands of publicly accessible images generated by the community are freely available on Docker Hub. Finding photographs that are suitable for your purposes and are available for download and use with little to no alteration is surprisingly simple.
- Modularity and Scalability: Docker makes it simple to split up the functionality of your application into separate containers. You might, for instance, run your Redis server in one container, your Postgres database in another, and your Node.js app in yet another. With Docker, connecting these containers to form your application has become simpler, making it simple to scale or upgrade individual components in the future.
Containers vs. Virtual Machines
Although virtual machines and containers resemble one another greatly, they cannot be used in place of one another. As a result, although some projects will provide users a choice between the two, others won’t. Lets look at a few differences:
- Virtual machines have their own operating system.Containers run on top of a physical server and its host operating system.
- Containers are smaller and more mortable. The amount of code required for a container to operate is significantly reduced when the operating system is shared. As a result, containers are substantially smaller than virtual machines (VMs), frequently taking up only a few megabytes as opposed to several gigabytes for VMs.
- Containers start up more quickly. Compared to starting a virtual machine, which requires starting a new OS, launching a container is substantially faster because the operating system is already up and running.
- All resources are accessible to containers. In a VM setup, the hypervisor allots particular resources to virtual machines. This may be advantageous for applications that demand a lot of resources, but it may also be ineffective when allotted resources go underutilized. Containers do not have this issue because they have access to all of the underlying hardware resources. Because of this, containers are frequently a better option for applications whose resource requirements are uncertain.
- Virtual machines are safer. A virtual machine is completely separate from the rest of the computer. Only at the process level is a container isolated. This improves the security of virtual machines. If the host operating system is compromised, all containers installed above it may be as well. Virtual machines would be unaffected in the same scenario.
Advantages of Containers
In addition to process separation, containers have a lot of other advantageous traits.
- Lighter: Unlike virtual machines (VMs), containers do not transport the whole OS instance and hypervisor with them. They only contain the OS dependencies and processes required for the code to run. For some VMs, container sizes are calculated in megabytes rather than gigabytes, which better utilizes hardware resources and has quicker startup times.
- Application portability is quite high because to the use of Docker containers. These portable programs can be simply transported anywhere as a single unit, and their functionality is unaffected.
- Density: Since Docker doesn’t employ a hypervisor, it makes better use of the resources that are at its disposal. Because of this, more containers can run on a single host than virtual machines can. Because of their great density and lack of resource overhead, Docker Containers perform better.
- Developer productivity is increased since containerized apps may be created once and run anywhere. Additionally, containers are quicker to deploy, provision, and restart than virtual machines. In addition to being a better fit for development teams following Agile and DevOps approaches, this makes them perfect for use in continuous integration and continuous delivery pipelines.
- Compared to virtual machines (VMs), containers allow developers to execute many more copies of a program on the same hardware. This may result in lower cloud costs.