Is there any software similar to docker?

There are software similar to docker: 1. Podman, which is an open source Linux native container engine without a daemon; 2. LXD, which is an open source container engine designed specifically for LXC Linux containers; 3. Buildah, which is It is an OCI image building tool developed by Red Hat for containerized systems; 4. RunC, etc.

The operating environment of this tutorial: linux7.3 system, docker version 20, Dell G3 computer.

There is software similar to docker.

Docker was born in 2013 and popularized the concept of containers, so much so that most people still equate the concept of containers with "Docker containers".

As the first to adopt the technology, Docker sets the standards that new entrants must adhere to. For example, Docker has a large system image library. All alternatives must use the same image format while attempting to change one or more parts of the entire stack on which Docker is based.

During this period, new container standards emerged and the container ecosystem developed in different directions. Nowadays, there are many ways to use containers besides Docker.

Container management software similar to docker

1, Podman

Podman is a daemon-less open source Linux native container engine developed by RedHat, which is used to build, run and manage Linux OCI containers and container images. Although Podman provides a command line interface similar to Docker, it does not operate in the same way.

One significant difference between Docker and Podman is that Docker runs a persistent, self-sufficient runtime to manage its objects or daemon called dockerd; while Podman does not rely on a daemon to work. Instead, Podman starts the container as a child process. It also interacts directly with the registry and the Linux kernel using runtime processes. For this reason, Podman is called a daemonless container technology.

The absence of a daemon increases Podman's flexibility as a container engine and eliminates dependence on a single process. Another big difference between Podman and Docker is that it does not require root privileges. This feature provides an additional safety buffer, limiting certain potentially dangerous processes that could manipulate critical system settings and make the container and contained applications vulnerable.

Additionally, Podman can run pods - collections of one or more containers, managed as a single entity, and utilizing a shared resource pool. With this capability, Podman users can move their workloads to Kubernetes.

2. LXD

LXD is an open source container engine designed specifically for LXC Linux containers. LXC enables users to run applications in isolated containers or virtual environments similar to virtual machines without the technical burden of managing individual cores. LXD provides an interface to the LXC software library and creates a daemon process that handles networking, data storage, and management of multiple LXC containers. Although LXC can be run as a standalone tool, it has a limited subset of functionality. LXD provides these additional features and therefore relies on LXC to work.

The main differences between LXD and Docker are as follows. Unlike Docker's design pattern that recommends a single process per container, containers in LXC/LXD can run multiple processes. Additionally, Docker containers are more portable, effectively abstracting resources compared to LXD. Finally, Docker supports running on Windows and macOS environments, but LXD only supports Linux.

3. containerd

containerd is an advanced container runtime that provides an interface between the operating system and the container engine by running runc at the bottom. runc is a daemon supported on Windows and Linux that abstracts operating system-specific functionality to make it easier to run and oversee containers and manage image transfers and storage.

This level of abstraction provided by containerd eliminates the complexity of making several low-level system calls, allowing container portability. However, unlike Docker, containerd does not handle image building or volume creation. Interestingly, containerd was the default runtime for Docker and is now a standalone tool, just like runc. This also makes containerd a convenient orchestration tool like Kubernetes, one of the most popular Docker alternatives.

4. Buildah

Buildah is an OCI image building tool developed by the Red Hat Foundation for containerized systems. It is a tool that provides functionality similar to running `docker build` in Docker. Buildah is often used together with Podman to complement each other. For example, Podman uses a subset of Buildah functionality under the hood to implement its build process.

It can build images from a Dockerfile or Containerfile and produce the same images as those created with Docker because these images are OCI compliant. In addition, it provides fine-grained control over image layers, allowing multiple modification commits in a single layer. It also provides the ability to build an image from scratch, an image that contains no content, which gives users the freedom to add only the packages required to run the application. Finally, unlike Docker, in Buildah users can only see the images they build.

5. BuildKit

BuildKit is a second-generation Moby project that builds images and is available as an experimental feature in newer Docker versions. Like Docker, it runs using a daemon. However, one of the main differences between standard Docker builds and BuildKit is that the former builds layer by layer, while the latter provides parallel build processing. This feature improves performance and makes builds faster. BuildKit also allows skipping unused stages, improves incremental builds, and allows rootless builds. Additionally, BuildKit uses a cache to reduce the need to rebuild each layer of the image.

6. Kaniko

Kaniko is a Google image building tool that can build images from Dockerfiles. It is daemonless like Buildah, but focuses more on building images in Kubernetes. Kaniko is not very convenient for local development instances because it is usually run as an image with a container orchestrator such as Kubernetes. Kaniko can be a useful tool for continuous integration and delivery pipelines in Kubernetes clusters.

7. RunC

RunC was previously a module embedded into the Docker architecture and was released as a standalone tool in 2015. It has since become a widely used, standardized, and interoperable container runtime. DevOps teams can use it as part of Docker or other custom container engines. RunC belongs to the container runtime part of the containerization ecosystem. The container runtime is the lower-level component used in the container engine that handles container running.

Recommended learning: "docker video tutorial"

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