Bocker: Docker implemented in around 100 lines of Bash (2015)

Original Article ↗ Hacker News Discussion ↗

A tiny Bash project that reimplements core Docker features in about 100 lines is prompting renewed interest in how containers really work under the hood—mainly as glue around existing Linux primitives like namespaces, cgroups, and union filesystems. Commenters contrast this minimal approach with Docker Inc.’s commercial products, debating where Docker’s real value lies (image format, Desktop tooling, ecosystem) and highlighting alternatives such as Podman, Rancher Desktop, and Orbstack, especially on macOS and Windows. Many see Bocker primarily as an educational tool that demystifies containers rather than a practical replacement for production use.

Simplicity of Docker / Role of Bocker

  • Bocker shows that core Docker functionality is mostly “glue” around existing Linux features: namespaces, cgroups, union/overlay filesystems.
  • Many see this as both Docker’s strength (built on solid primitives) and a business risk (easy to re-implement).
  • Commenters emphasize Bocker as an educational tool to demystify containers, not a production replacement.

Where Docker Adds Value (and Where It Doesn’t)

  • Several argue Docker’s real value is in the image/OCI format and distribution workflow (caching, layering, “run anywhere”), not the runtime itself.
  • Some feel Docker should have doubled down on PaaS (like Cloud Run/Fly/Render) rather than Swarm, which is viewed as a failure vs Kubernetes.
  • Others note Docker became profitable focusing on Docker Desktop + Hub and standardization, not orchestration.

Alternatives on macOS/Windows/Linux

  • Strong criticism of Docker Desktop on macOS: seen as bloated, slow (VM + networked FS), and license-frustrating.
  • Popular alternatives mentioned: Rancher Desktop, OrbStack, Colima, Podman (with/without Podman Desktop), lazydocker as a TUI.
  • Some report smooth migrations to Rancher Desktop/OrbStack; others describe painful failed migrations away from Docker Desktop due to subtle filesystem/network integration issues and script compatibility.
  • OrbStack is praised for efficiency and UX but has reported IPv6-related DNS issues for Kubernetes pods.

FOSS, Podman, and “Container ≠ Docker”

  • Multiple comments highlight Podman, runc, systemd-nspawn, LXC, and rootless approaches as open alternatives.
  • Debate over how “open” Docker is: core CLI/daemon/buildkit/compose are open source; Docker Desktop GUI and its license are proprietary.
  • Some think Docker is “lucky” that people equate containers with Docker; Podman is seen as a superior drop-in in some contexts.

Technical Details & Gotchas

  • Rootless containers on Linux are described as hard, especially networking; tools like rootlesskit and slirp4netns trade performance and security.
  • Docker on macOS/Windows always implies a Linux VM, with performance implications and limited GPU/MPS support.
  • Overlayfs (or ZFS/Btrfs snapshots) is cited as a powerful technique for speeding up large CI checkouts.
  • Warnings about manually compiling util-linux (risk of breaking mount), and about old distro Docker packages lagging features (buildx, modern compose).

Meta / Learning / Misc

  • Many enjoy small Bash tools (like Bocker, minimal load balancers, chroot/proot wrappers) as a way to truly understand infrastructure.
  • There is acceptance that many GitHub projects have unfinished TODOs; sometimes software is simply “done.”