Beyond Docker: Exploring Top Container Runtime Alternatives

According to 2018 statistics, Docker held 83% of the container market, down from 99% in 2017, indicating a decline in its dominance.

The article examines several Docker alternatives, comparing their features, advantages, and drawbacks.

CoreOS rkt

In 2018, rkt captured 12% of the market. It supports Docker and appc images, integrates directly with Kubernetes (often called rktnetes), and can be deployed with a single command: $ kubelet --container-runtime=rkt rkt also supports TPM for enhanced security and optimizes application containers, though it lacks some third‑party integrations and full OCI compatibility. Its compatibility aids public‑cloud migration and rapid deployment.

Mesos Container Engine

Mesos accounted for 4% of the market in 2018. As an Apache open‑source project, it offers strong performance, supports Docker and appc images, and is expected to add OCI support soon. It is best suited for big‑data processing platforms combined with Spark or Flink.

However, Mesos containers must run through the Mesos framework, unlike other runtimes that can run independently.

LXC Containers

LXC, representing the remaining 1% market share, predates Docker and is sometimes called “a chroot on steroids.” It consists of the lxc runtime, the Go‑based daemon lxd, and the filesystem manager lxfuse. Lxd provides a graphical interface and CLI, improving user experience.

According to Aquasec, lxd simulates a VM‑like environment with lower overhead, and it is accessible from Windows and macOS. LXC currently lacks Kubernetes integration and full OCI support, though the upcoming lxcrun aims to address these gaps.

OpenVZ

OpenVZ, released in 2005 as a Linux kernel extension, offers OS‑level virtualization with minimal memory consumption by sharing the host kernel. It is unsuitable for single‑application scenarios and lacks CRI or Kubernetes integration; stability concerns have been raised for OpenVZ 7.

Containerd

Containerd is an industry‑standard container runtime focused on simplicity, robustness, and portability. As a CNCF incubating project, it runs as a daemon on Linux and Windows, supports OCI images, integrates with gRPC, and provides comprehensive container lifecycle management.

Other Container Runtimes

Windows Server containers

Linux VServer

Hyper‑V containers

Unikernels

Java containers

Conclusion

Docker remains the most popular container solution and will stay dominant for some time, but in specific scenarios its advantages diminish. The rise of “de‑Dockerized” solutions may impact the Docker ecosystem. Evaluating OCI compatibility, portability, community activity, and real‑world adoption is essential when choosing a container tool.

Key assessment: Docker is still king, but signs of decline are evident – 2018 Sysdig report