Container virtualization of applications as an effective complement to virtual machines

With the help of container virtualization, you can create stable environments for applications that run isolated from one another on the host system. While several virtual machines (VMs) on a server each use their own operating system, only one operating system runs in container virtualization for several containers. Therefore, virtualizations with containers are considered to be particularly resource-friendly compared to hypervisor virtualizations. Learn more about the possibility of application virtualization and how you can use it to complement virtual machines in a meaningful way.

What is a container in virtualization?

To put it simply, containers consist of processes that are isolated from the host operating system and work independently. All the parameters required to run the respective application are included, such as files, dependencies and configurations. The applications can therefore be moved quickly and easily to another host operating system, for example to test them there. The special feature of the containers is that the guests use the kernel of the host operating system, while virtual machines require an operating system to be installed.

Where is the technology used?

An important area of ​​application for container virtualization is the reliable execution of software in a different environment. Developers use the technology, among other things, as a test environment because of its user-friendly and resource-saving application options. For example, containers are ideal for microservices technology. Microservices are an architecture model for software development and are used for the efficient modularization of software. Complex software is developed as a distributed system with independent services. Microservices can be developed independently of the overall system and run on different server instances. Containers are the ideal packaging for this. In this way, microservices and other workloads such as web apps or web servers can be quickly deployed and scaled.

Why is container virtualization more efficient for applications?

Compared to virtualization with a hypervisor (an abstraction layer between hardware and operating system), container virtualization is considered to be more resource-efficient in the application area. Since no hypervisor is used, containers require less CPU power, memory and storage space overall. For example, an application in a container can only be a few megabytes in size, while a virtual machine usually requires several additional gigabytes for the operating system. As a result, many more containers fit on server hard drives than virtual machines. And since there are no guest operating systems to boot, containerized applications launch much faster than virtual machines.

What are the advantages and disadvantages of app virtualization with containers?

Several containerized programs share the operating system and are still isolated from each other and from the overall system. This results in advantages but also disadvantages compared to virtual machines. Here is an overview:

Advantages of the containers:

• Containers use system resources more efficiently in applications than virtual machines.
• Instances of containerized programs consume less main memory.
• Containers start and stop faster.
• The more efficient utilization of resources saves IT costs.
• An operating system must be installed for each virtual machine on a host system, accordingly you need the software licenses for the operating systems. With container virtualization, one license for the host's operating system is sufficient, which reduces costs for software licenses.
• Containers encapsulate all the resources needed to run the program, so they can be moved to different environments and started there easily.
• Containers are the perfect packaging for microservices and other workloads such as web apps or web servers.

Disadvantages of the containers:

• Different containers use the same kernel. This is a central element of the operating system and, as the lowest software layer in the system, has direct hardware access. Because the containers share the kernel with the host operating system, one container can compromise other containers and compromise security. Therefore, virtual machines provide better isolation than containers.
• Although applications can often be moved from a VM to a container, this does not automatically make sense.

Why are virtual machines still important in virtualization?

The main differences between container virtualization and such virtual machine solutions relate to security, scalability and portability: while VMs can run different operating systems, a container can only run one type of operating system. For example, only containers with a Linux operating system run on a Linux server, the guest systems use the kernel of the host operating system. With container virtualization, you can configure which system resources the containers can access. This is different with the virtual machines: With these, for example, you can install numerous different Linux distributions in the VMs on a host with Windows 10 and use them independently of one another. Containers are also used to test the compatibility of software in a virtualized operating system in full depth only conditionally suitable. Problems that arise are more difficult to solve. It may make more sense here to virtualize with VMs.

Another issue concerns security: you can think of the difference as between a detached house (VM) and an apartment (container). In single-family houses, each owner is responsible for their own security, unsafe front doors at neighbors do not pose a risk. This corresponds to the virtual machines with their strong insulation. In the case of apartments, however, all residents are affected if someone leaves the common entrance open.

Docker - the platform for easy container virtualization

One of the quickest ways to container applications is programmatically Docker desktop for Linux, Windows and macOS. Virtualization with Docker simplifies isolation and deployment. The open source project was released in 2013 and has been causing a sensation ever since. IT giants such as IBM, Red Hat and Microsoft have already participated in the technology. No wonder: the container virtualization contains all the necessary packages, and Docker containers can also be used on different hosts. You can run Docker containers on the laptop or in a public cloud if the Docker runtime is installed.

Notice: Docker develops solutions for cloud servers and clustering. alternatives are FreeBSD jails, Solaris Zones and the Linux command line tool rkt.

Summary

Container virtualization and docking technology gives software developers more freedom and the ability to create applications that can respond quickly to changing conditions. Basically:

• Containers are more suitable as a complement to VMs than as a replacement due to the lower security of isolation. Compared to the virtual machines, resources for virtual operating systems, drivers and system files are saved.
• Containers share the files of the host operating system, so they are smaller, start faster and are easier to manage.
• Organizations can install more containers than VMs on servers, potentially making better use of resources.

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Cover motif: Photo by Aron Yigin on Unsplash