Docker — Trivia & Interesting Facts¶
Surprising, historical, and little-known facts about Docker.
Docker did not invent containers — it made them usable¶
Linux containers existed for years before Docker. LXC (Linux Containers) launched in 2008, and Google had been running everything in containers internally since 2004 using a system called Borg. Docker's breakthrough in 2013 was not the technology — it was the developer experience: a simple CLI, a Dockerfile build format, and Docker Hub for sharing images. Solomon Hykes has said Docker was "the apt-get of containers."
Docker was a pivot from a failed PaaS company¶
Docker Inc. was originally called dotCloud, a Platform-as-a-Service startup founded by Solomon Hykes in 2010. When dotCloud failed to compete with Heroku, Hykes open-sourced the internal container engine as a last-ditch pivot. The project exploded at PyCon 2013, and within months dotCloud was renamed to Docker Inc. The dotCloud PaaS was eventually sold to cloudControl (which also went bankrupt).
Docker was originally written in Python, then rewritten in Go¶
The first prototype of Docker was a Python wrapper around LXC. Hykes rewrote it in Go because Go produced static binaries that were easy to distribute, had built-in concurrency, and compiled fast. This decision was pivotal — Go's single-binary deployment model meant Docker could be installed with a single curl command, which was radical in 2013.
The Moby Project confusion was entirely self-inflicted¶
In April 2017, Docker Inc. renamed the open-source Docker engine to "Moby" and repositioned "Docker" as the commercial product name. The community was furious and confused. GitHub issues flooded in from people who could not figure out if Moby was Docker, replaced Docker, or was something else entirely. The rebranding is widely considered one of Docker's worst community relations decisions.
Docker almost died as a company — twice¶
Docker Inc. raised $273 million in venture capital but struggled to monetize. By 2019, the company was reportedly running low on cash. In November 2019, Mirantis acquired Docker Enterprise (the Kubernetes and Swarm platform) and Docker Inc. refocused on developer tools. The company nearly ran out of money again before pivoting to Docker Desktop subscriptions, which finally achieved profitability around 2022.
docker run creates five namespaces and a cgroup in milliseconds¶
When you run docker run, the runtime creates a PID namespace (isolated process tree), a network namespace (its own IP), a mount namespace (its own filesystem), a UTS namespace (its own hostname), and an IPC namespace (its own shared memory) — plus a cgroup for resource limits. All of this happens in under 100 milliseconds on modern hardware, compared to 30-60 seconds for a virtual machine.
Docker Hub serves over 13 billion image pulls per month¶
As of 2023, Docker Hub was serving approximately 13 billion pulls per month, making it one of the highest-traffic package registries in the world. In November 2020, Docker imposed rate limits (100 pulls per 6 hours for anonymous users) that broke CI pipelines worldwide. The backlash led to exemptions for open-source projects and accelerated adoption of alternative registries like GitHub Container Registry and Amazon ECR Public.
The docker.sock file is the most dangerous file on a Docker host¶
Mounting /var/run/docker.sock into a container gives that container full control over the Docker daemon — including the ability to start privileged containers, mount the host filesystem, and effectively gain root on the host. Despite this, countless tutorials and CI tools recommend mounting it. It is the most commonly exploited attack vector in container environments, and the primary reason rootless Docker was developed.
Docker Compose was originally a separate company's product¶
Docker Compose started as a project called "Fig," created by Orchard Laboratories (Ben Firshman and Aanand Prasad) in 2013. Docker acquired Orchard in 2014 and renamed Fig to Docker Compose. The original Fig YAML format became the docker-compose.yml format used by millions today. Compose V2, rewritten as a Docker CLI plugin in Go (replacing the Python original), shipped in 2022.
COPY --chown saved millions of wasted layers¶
Before Docker 17.09 added --chown to the COPY instruction, changing file ownership required a separate RUN chown -R command. This created an entirely new layer containing a complete copy of the files — effectively doubling the space used. For a 500 MB application directory, this meant 1 GB in the image just for ownership metadata. The --chown flag applies ownership during the copy, using zero extra space.
Docker Swarm lost the orchestration war despite being simpler¶
Docker Swarm mode (built into Docker Engine in 2016) was dramatically simpler than Kubernetes — a three-node cluster could be created with two commands. Despite this, Kubernetes won decisively by 2018. The primary reason was ecosystem: Kubernetes had CNCF backing, a massive contributor community, and a pluggable architecture that attracted vendors. By 2023, Docker officially recommended Kubernetes for production orchestration.
The whale in the Docker logo is named Moby Dock¶
Docker's logo whale, carrying containers on its back, is officially named "Moby Dock." The name predates the Moby Project controversy. The whale represents Docker carrying and transporting standardized containers — a direct analogy to shipping containers, which revolutionized global trade by standardizing cargo dimensions. The container metaphor was central to Docker's marketing from day one.
Docker Desktop's license change affected millions of developers¶
In August 2021, Docker changed Docker Desktop's license to require a paid subscription for companies with more than 250 employees or over $10 million in revenue. The change affected millions of developers and triggered a migration to alternatives like Podman, Rancher Desktop, and Colima. It also drove development of Docker Engine's rootless mode as a Desktop-free alternative on Linux.