Docker vs Qemu: What are the differences?

Docker is a platform for developing, shipping, and running applications in containers, providing lightweight and portable environments, while Qemu is an open-source emulator that allows users to run operating systems and virtual machines on various host platforms. Let's explore the key differences between them.

1. Architecture: Docker uses a containerization approach, where multiple containers can run on a single host operating system. Qemu, on the other hand, is a full-system emulator that provides hardware virtualization, allowing different operating systems to run simultaneously.

2. Performance: Docker containers are lightweight and share the host OS kernel, resulting in faster startup times and lower resource usage compared to Qemu virtual machines, which require full OS emulation.

3. Isolation: Docker provides process-level isolation, meaning that containers share resources but are isolated at the process level. Qemu, on the other hand, provides full isolation between virtual machines, allowing each VM to have its own resources and kernel.

4. Compatibility: Docker relies on the host OS kernel, making it more compatible with a wider range of operating systems and applications. Qemu, on the other hand, can emulate different hardware architectures, making it more suitable for running operating systems that are not supported natively on the host system.

5. Deployment: Docker containers are highly portable and can be easily deployed across different environments, whether it's on-premises or in the cloud. Qemu virtual machines are more suitable for running guest operating systems on a specific host, making them less portable.

6. Resource Usage: Docker containers share the host's operating system and resources, resulting in more efficient resource utilization compared to Qemu virtual machines, which require dedicated resources for each VM.

In summary, Docker simplifies the process of containerization, enabling developers to package applications and their dependencies into isolated environments for deployment across different systems with ease. On the other hand, Qemu offers a versatile emulation solution for running virtual machines, providing flexibility for testing and development purposes across a range of hardware architectures and operating systems.