A virtual machine is essentially software that operates as if it were a separate computer. Each virtual machine environment duplicates the operating system and virtualizes necessary hardware.
A Docker container is similar, but runs on a virtual operating system and containerizes its code and dependencies in isolation so it can run within any computing environment.
Choosing between Docker containers and virtual machines isn’t hard when you have a solid understanding of each environment’s strengths and weaknesses. There are instances where a virtual machine is the better option (as with VPS hosting), but sometimes Docker containers are the way to go.
While virtual machines won’t replace Docker containers, several features make Docker containers the superior choice for certain applications.
1. A virtualized operating system
Virtual machines virtualize hardware while containers virtualize the operating system. This makes a profound difference in performance and lightens the load on the server. Each virtual machine requires a full copy of the operating system, application, binaries, and libraries. This takes up a significant amount of space – in the Gigabytes – for each virtual machine.
Containers, on the other hand, share one installation of the operating system, binaries, and libraries. All containers share the machine’s operating system kernel so there is no need to run multiple operating systems for each container. This makes containers portable and the server efficient.
Containers also take up far less space than a virtual machine, usually in the tens of Megabytes. Virtualizing the operating system rather than the hardware means containers can handle more applications.
2. Easy security monitoring
As with every project that uses open source libraries, it’s important to monitor performance and security. That’s easy to do with Docker containers. White Source Software recommends monitoring security policies along with performance and application metrics. There are container scanning tools that will specifically look for unsafe open source libraries.
2. Docker containers are designed for secure isolation
According to Docker.com, Docker containers provide “the strongest default isolation capabilities in the industry.”
Docker containers were created to fulfil developer requirements to isolate application dependencies from infrastructure.
3. Docker containers are smaller than virtual machines
When it comes to virtual environments, size matters. A Docker container is much smaller than a virtual machine, which enables faster start-up and better performance.
Docker containers use less resources than a virtual machine and can be much faster. For instance, a Docker container can be created and launched within seconds, as compared to the several minutes it takes to create and launch a virtual machine.
According to DevOps.com, container applications offer superior performance compared to applications running within a virtual machine.
3. Docker containers resolve “dependency hell”
Operations teams often run into compatibility problems with virtual machines and their dependencies. An application might work on someone’s laptop, but not on desktop or mobile. This is due to the tangled web of conflicts that arise from too many dependencies. These conflicts, which often result in bigger problems, are what developers call “dependency hell.”
A virtual operating system allows containerized applications to run on any device. Since each container is isolated with everything needed to make the software run, dependency issues are avoided and performance is consistent.
4. Docker is an open source container platform
The Docker container platform is built on several different open source technologies including the Docker Engine, Docker Desktop, Docker Hub, and Kubernetes. Millions of images are available that have been contributed by the community and verified publishers.
5. High security
When using the Docker Enterprise, container image authenticity is confirmed with cryptographic digital signing. This means your team can identify the author of any application and whether it’s been tampered with.
The automation of security insights makes it easier to meet compliance requirements and avoid security breaches.
Docker containers are a great DevOps tool
While virtual machines are more flexible, Docker containers are perfect for applications that require isolation to prevent dependency issues. Docker containers are useful for porting application stacks across the cloud, and they’re often used in conjunction with virtual machines.
Although Docker containers are becoming popular, virtual machines won’t be phased out anytime soon. For now, Docker containers and virtual machines are being used in tandem to create a superior user experience.