--- title: EP221: How Docker Works Under the Hood | daily.dev description: A newsletter covering several system design topics. The main piece explains how Docker works internally: the CLI sends an API call to dockerd, which delegates... canonical: https://daily.dev/posts/ep221-how-docker-works-under-the-hood-iajqja6ba twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: EP221: How Docker Works Under the Hood | daily.dev og:description: A newsletter covering several system design topics. The main piece explains how Docker works internally: the CLI sends an API call to dockerd, which delegates... og:url: https://daily.dev/posts/ep221-how-docker-works-under-the-hood-iajqja6ba og:image: https://api.daily.dev/og/posts/IaJQJA6ba.png og:image:alt: EP221: How Docker Works Under the Hood og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # EP221: How Docker Works Under the Hood **[ByteByteGo](https://daily.dev/sources/bytebytego)** · 7 min read · 23 upvotes · 3 comments ## Summary A newsletter covering several system design topics. The main piece explains how Docker works internally: the CLI sends an API call to dockerd, which delegates to containerd, which calls runc to create Linux namespaces and cgroups — no hypervisor involved. Other sections cover git merge vs rebase trade-offs, a comparison of 12 vector databases (Pinecone, Weaviate, Milvus, Qdrant, etc.), pagination strategies for large datasets (offset, keyset, cursor, time-based), and how LLMs orchestrate sub-agents for deep research tasks. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Community discussion Top comments from developers on daily.dev. **@bobbyiliev** · 2 upvotes > Love the diagrams. **@pdfopsdev** · 0 upvotes > The 'no hypervisor' part is the bit people trip over — it's only true on a Linux host. On Docker Desktop for Mac or Windows there's a full Linux VM underneath, because namespaces and cgroups are kernel features and there's no Linux kernel to borrow otherwise. Worth stating explicitly, since it's why a 'lightweight' container can still cost you real VM overhead on a laptop. **@netgeo360** · 0 upvotes > The best way to understand how Docker works is, in my opinion, through a combination of traditional learning and AI-assisted development. Start with the "old-school" approach: set up your local environment, read the official documentation, and build a small project from scratch. Once you have that foundation, use AI to improve your implementation, explore alternatives, and deepen your understanding. > > From what I've observed, many junior DevOps engineers rely too heavily on AI to generate Dockerfiles or Docker Compose configurations without fully understanding what they're doing. I understand... ## Similar posts on daily.dev - [A Decade of Docker Containers – Communications of the ACM](https://daily.dev/posts/a-decade-of-docker-containers-communications-of-the-acm-gqu80q4ol) · Hacker News · 1 upvotes · 0 comments - [EP179: Kubernetes Explained](https://daily.dev/posts/ep179-kubernetes-explained-y0on3jcsg) · ByteByteGo · 33 upvotes · 0 comments - [Docker's secret ingredient came from a 1992 operating system that almost nobody used](https://daily.dev/posts/docker-s-secret-ingredient-came-from-a-1992-operating-system-that-almost-nobody-used-4x9cjopcm) · XDA Developers · 2 upvotes · 0 comments --- Tags: [#docker](https://daily.dev/tags/docker), [#containers](https://daily.dev/tags/containers), [#vector-search](https://daily.dev/tags/vector-search) [View this post on daily.dev](https://daily.dev/posts/ep221-how-docker-works-under-the-hood-iajqja6ba) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"EP221: How Docker Works Under the Hood","url":"https://daily.dev/posts/ep221-how-docker-works-under-the-hood-iajqja6ba","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/ep221-how-docker-works-under-the-hood-iajqja6ba"},"datePublished":"2026-07-11T15:34:02.668Z","dateModified":"2026-07-13T04:17:27.075Z","description":"A newsletter covering several system design topics. 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On Docker Desktop for Mac or Windows there’s a full Linux VM underneath, because namespaces and cgroups are kernel features and there’s no Linux kernel to borrow otherwise. Worth stating explicitly, since it’s why a ‘lightweight’ container can still cost you real VM overhead on a laptop.","datePublished":"2026-07-12T18:05:07.167Z","url":"https://daily.dev/posts/IaJQJA6ba#c-XeoEm1Bqx","author":{"@type":"Person","name":"PDFops","url":"https://daily.dev/pdfopsdev","image":"https://media.daily.dev/image/upload/s---8isRBKc--/f_auto/v1782922291/avatars/avatar_orjMeK8QKaaVZwGq7ScPz?_a=BAMAMicg0"}},{"@type":"Comment","text":"The best way to understand how Docker works is, in my opinion, through a combination of traditional learning and AI-assisted development. Start with the “old-school” approach: set up your local environment, read the official documentation, and build a small project from scratch. Once you have that foundation, use AI to improve your implementation, explore alternatives, and deepen your understanding.\nFrom what I’ve observed, many junior DevOps engineers rely too heavily on AI to generate Dockerfiles or Docker Compose configurations without fully understanding what they’re doing. I understand the current trend of “shipping fast with AI,” but I believe that great engineers are those who can quickly troubleshoot and resolve issues when things go wrong. A solid understanding of the underlying concepts is what enables that. To that end, architecture and workflow diagrams are also an excellent learning tool, as they help visualize how the different components interact.","datePublished":"2026-07-14T11:21:45.536Z","url":"https://daily.dev/posts/IaJQJA6ba#c-RL3wrQo4S","author":{"@type":"Person","name":"netgeo360","url":"https://daily.dev/netgeo360","image":"https://avatars.githubusercontent.com/u/69837387?v=4"}}]} ```