At the end of 2020, Kubernetes issued an announcement, officially announcing that it will stop supporting Docker starting from v1.24. However, the impact of Kubernetes deprecating docker on us should not be too alarming.
What are the following tools that can replace Docker? And what are the advantages over Docker?
containerd
containerd is a lightweight container daemon that provides a standard container API to manage container lifecycle, networking, and storage. It is designed to integrate with any container engine, cluster management system and operating system. Because of its lightweight and portability, container engines and cluster management systems can utilize containerd as their underlying runtime so that they can be perfectly integrated.
containerd is an open source project developed by Docker. It was originally a part of the Docker engine, but now it has become an independent project and has been certified by CNCF (Cloud Native Computing Foundation) as an incubation project. containerd is committed to providing a scalable, reliable, efficient and easy-to-manage container runtime environment for cloud native applications, and has become one of the most popular container runtime environments in the world.
Compared with docker, containerd has the following advantages
1. More lightweight: containerd is lighter than docker, and only includes basic container runtime functions, instead of including a complete container ecosystem like docker, thereby reducing a lot of complexity and redundancy.
2. More efficient: Compared with docker, containerd has higher performance and faster startup time, which makes it more suitable for building, running and managing containerized applications in large-scale production environments.
3. More stable: containerd is a platform with stable design, especially in handling high load, high concurrency and large-scale deployment. It is a component contributed by Docker to OCI (Open Container Initiative), which is widely supported and reviewed by the global community, so it is better guaranteed in terms of stability.
4. More reliable: containerd is a carefully tested and verified platform with higher reliability and availability. Its code has been vetted and tested by many companies and communities, making it a solid platform for developers to build production-grade container applications.
5. Easier to expand: containerd is scalable and flexible, and developers can extend its functionality by using external plug-ins without disturbing the core code. This gives developers more freedom to implement their own container management and application building strategies.
Podman
Podman is a container engine that manages and runs containers without a daemon. It provides a Docker-like CLI interface that allows users to create, manage, and deploy containers in a Docker-like manner. Podman does not require the use of the Docker daemon. Instead, it manages containers using a process manager that interacts with the host operating system.
Therefore, when creating and running containers in Podman, it does not create additional processes or daemons. Podman also provides multiple commands, such as pod, to manage container groups, such as multiple containers in a pod, running in a common namespace and in an isolated manner. Podman also provides a variety of methods for mounting storage to containers and other advanced container arrangements, and supports the OCI (Open Container Initiative) specification.
Both Podman and Docker are container runtime tools, but have the following advantages:
1. Better security. Podman does not require root privileges to run containers, which reduces security risks.
2. More lightweight. The Podman container engine can run without the need for a daemon and is therefore more lightweight than Docker.
3. Easier to manage. Podman containers can be managed directly as a Linux process, no additional daemons or management tools are required.
4. Easier to develop. Podman containers can be built directly using existing Dockerfiles without any modification.
5. More flexible. Podman supports integration with Kubernetes and can deploy containers in Kubernetes clusters.
6. More efficient. Podman can build containers in parallel, increasing build speed. To sum up, Podman is a safer, more flexible, more efficient, and lighter-weight container engine.
LXC/LXD
LXC (Linux Containers) is a container virtualization technology that allows running multiple isolated Linux system environments on the same physical host, each environment has its own independent namespace, file system, network and process space. Compared with traditional virtualization technology, LXC has higher performance, faster startup speed and less resource usage.
LXD (Linux Container Daemon) is an advanced encapsulation of LXC. It provides an easier-to-use and safer container management tool. It can manage containers through the web interface, command line tools, etc., and provides advanced features, such as image management, network management, backup and recovery, etc. LXD is often used in scenarios such as building cloud platforms, developing and testing environments, and containerized applications. It is currently one of the most active and popular container managers in the Linux container ecosystem.
The advantages of LXC/LXD over docker include:
1. More lightweight virtualization: LXC provides system-level virtualization, while Docker provides process-level virtualization. As a result, LXC has a relatively small resource footprint, is faster to start and stop, and has smaller images.
2. Higher isolation: Compared with Docker's process-level isolation, LXC provides system-level isolation, which can achieve higher isolation. For example, LXC supports additional security measures, such as kernel security modules, limiting memory resources, etc.
3. More comprehensive operating system support: LXD can manage many different container operating systems, including Ubuntu, Debian, CentOS, Fedora, etc., while Docker can only run on the Linux operating system.
4. More suitable for applications that need to integrate multiple components: LXD allows multiple containers to access and communicate with each other, so it is suitable for deploying more complex applications, such as web application services and database services.
5. More complete management tools: The management tools LXCFS and LXDUI provided by LXD can help administrators better manage containers and improve operational efficiency.
In short, LXC/LXD has advantages in some aspects, such as lighter weight, more isolation, and support for multiple operating systems. But Docker also has its unique advantages, and other virtualization technologies cannot replace it in terms of lightweight and rapid deployment. Therefore, when choosing a virtualization technology, you need to choose according to your specific needs.
rkt
rkt is an efficient, secure, and lightweight application container engine, an open source project based on the CoreOS Linux distribution. rkt uses a strong proposal-based security model to protect its internal operating system and containers, while providing good interoperability and flexibility to deploy and manage containerized applications in a variety of environments. The design philosophy of rkt is a simple two goals: to ensure system security and compliance with application container standards. To achieve these goals, rkt adopts three main design ideas: ease of use, transparency, and portability.
Advantages of rkt over Docker include:
1. Higher security: rkt supports security mechanisms such as hardware isolation and SELinux, which can provide better security.
2. Better performance: rkt has a simpler architecture, faster startup, and less resource usage, so it runs more efficiently.
3. The lifecycle management of containers is more convenient: rkt can modularize the lifecycle management of containers, so that users can manage containers more flexibly.
4. Openness and standardization: The development of rkt is completely open source, and because it conforms to the standardized container format, it can be integrated with other container management software and cloud platforms.
5. More lightweight: rkt does not need to use Docker's huge image management system, so the image is more lightweight.
OpenVZ
OpenVZ is an open source virtualization platform based on Linux kernel virtualization technology. It provides a lightweight virtualization technology that can create multiple isolated virtual environments (containers) on a single Linux operating system, and make each container They are isolated from each other, thereby improving system resource utilization and security. OpenVZ's containers run on a single Linux kernel and share the host system's hardware, memory, CPU, and network resources. Compared with other virtualization technologies, OpenVZ containers start faster and occupy less resources, so they are widely used in lightweight application scenarios, such as Web servers and database servers.
Advantages over Docker include:
1. High resource utilization: OpenVZ can better utilize the resources of the underlying physical host because it uses a shared kernel. This means that each container only needs to use the necessary resources (memory, CPU, network bandwidth, etc.), rather than having a full copy of the entire virtual operating system.
2. Better security: OpenVZ provides better security because it uses hardware isolation and virtualization technology so that containers are completely isolated and protected from other containers.
3. Better performance: OpenVZ is faster than Docker because it can directly interact with the operating system, while Docker has additional image layers and virtual machines. These extra layers require additional CPU and I/O cycles, reducing Docker's performance.
4. Easier to manage: Since OpenVZ uses a single core and shares the host operating system, it is easier to manage. This allows system administrators to more quickly and easily deploy, maintain and govern all containers.
5. More stable: Since OpenVZ uses hardware isolation technology and assigns specific system resources to each container, it is more stable. Docker containers may crash unexpectedly in a multi-node environment, while OpenVZ does not.
Singularity
Singularity is an open source container platform, mainly for scientific computing, engineering simulation and other high-performance computing fields. Different from traditional container technology, Singularity uses Linux container technology and adds some other features to make it easy to use in high-performance computing environments.
Singularity supports running arbitrary binaries as root in a ready-to-run container without installing any software or modifying environment settings on the host. Singularity also provides some features, such as the ability to run applications as users in containers, containers to automatically mount host file systems, and more. Singularity also supports the migration of containers between different nodes, and the ability to dynamically adjust the resource limits of containers at runtime, enabling scalability and advanced dynamic scheduling. Its use is becoming more and more common, especially in scientific computing and engineering simulation.
As one of the cutting-edge technologies of AI and machine learning, Singularity has the following advantages over Docker:
1. Avoid version conflicts - Singularity supports the use of system-managed underlying libraries and tools, so version conflicts and dependency issues can be avoided.
2. Security - Docker is a cloud-oriented tool, while Singularity pays more attention to the security and stability of the local environment.
3. Simple and easy to use - Singularity is suitable for remote HPC clusters and supercomputing centers. It aims to provide scientists, researchers, and developers with an easy-to-use framework for rapidly developing and deploying new AI and machine learning applications.
4. Repeatability - Singularity can ensure consistency and repeatability when running the same task on different systems, which is one of the important considerations in scientific research and experimental development.
In summary, Singularity is designed to provide researchers and developers with a safer, more reliable, easier-to-use and more repeatable AI and machine learning environment.
CRY IT
CRI-O is a container runtime tool that can easily run OCI containers in Kubernetes. It is a lightweight tool completely based on the standard container framework (OCI) specification. It uses the Kubernetes CRI interface to interact with the Kubernetes cluster. . CRI-O makes running containers easier, safer and more efficient, and enables developers to create and run containers using their favorite toolchain. Furthermore, CRI-O enables efficient resource utilization and greater flexibility of computer infrastructure, which greatly improves the scalability and portability of containers for faster development and higher productivity.
CRI-O is a lightweight container runtime designed specifically for Kubernetes. Compared with Docker, it has the following advantages:
1. More lightweight: CRI-O has less code than Docker, and the runtime image is also lighter than Docker.
2. More secure: CRI-O is more secure, it uses multiple mechanisms to protect containers, such as seccomp, SELinux, AppArmor, etc.
3. Faster: CRI-O is faster than Docker at launching containers because it only runs the programs needed at runtime, rather than the entire Docker engine.
4. More stable: CRI-O is specially designed for Kubernetes, so it is more suitable for use in Kubernetes, and it can be better integrated with Kubernetes.
5. More flexible: CRI-O supports multiple container image formats, including Docker, OCI, etc.
6. Easier to manage: The management method of CRI-O is similar to that of Docker, and operations such as starting, stopping, and deleting containers can be easily performed. At the same time, the integration of CRI-O and Kubernetes is easier.