Brief History of Containers

Container technology has a fascinating history, marked by innovations that have transformed how applications are developed, deployed, and managed.

The concept of isolation dates back to the chroot system call in Unix operating systems, which was introduced in the 1970s. Chroot allows a process to have its own isolated view of the filesystem.

FreeBSD introduced the concept of jails, which provided lightweight virtualization by isolating processes, filesystems, and networking. This was an early form of containerization.

Sun Microsystems developed Solaris containers, a more advanced form of OS-level virtualization. It allowed multiple instances of Solaris to run on a single host, each isolated from the others.

The Linux kernel introduced cgroups (control groups) and namespaces, laying the groundwork for containerization. These features enabled resource isolation (cgroups) and process isolation (namespaces).

LXC was one of the first attempts to create a user-friendly interface for Linux containers. It used cgroups and namespaces to provide process and resource isolation.

Docker revolutionized container technology by making it accessible to a broader audience. Docker introduced a user-friendly command-line interface and standardized container images using Dockerfiles. This allowed developers to package applications and their dependencies in a consistent manner.

With the rise of microservices and the need to manage and scale containers efficiently, container orchestration tools such as Kubernetes (originally developed by Google), Docker Swarm, Apache Mesos or Hashicorp’s Nomad gained popularity. These tools automate the deployment, scaling, and management of containerized applications.

To standardize container formats and runtimes, Docker and other industry leaders founded the OCI. The OCI specifications define the Open Container Format (OCF) for container images and the Open Container Runtime (OCR) for container runtimes.

Docker donated its container runtime, containerd, to the Cloud Native Computing Foundation (CNCF). Containerd is now a core component of many container platforms and orchestration tools.

While Docker remains popular, alternative container runtimes like containerd and Podman have gained traction. These tools provide flexibility and address some of the concerns associated with Docker.