How Linux is built with Greg Kroah-Hartman

The Pragmatic Engineer

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Linux is the most widespread operating system, globally – but how is it built? Few people are better to answer this than Greg Kroah-Hartman: a Linux kernel maintainer for 25 years, and one of the 3 Linux Kernel Foundation Fellows (the other two are Linus Torvalds and Shuah Khan). Greg manages the Linux kernel’s stable releases, and is a maintainer of multiple kernel subsystems.

We cover the inner workings of Linux kernel development, exploring everything from how changes get implemented to why its community-driven approach produces such reliable software. Greg shares insights about the kernel's unique trust model and makes a case for why engineers should contribute to open-source projects. We go into:

• How widespread is Linux?

• What is the Linux kernel responsible for – and why is it a monolith?

• How does a kernel change get merged? A walkthrough

• The 9-week development cycle for the Linux kernel

• Testing the Linux kernel

• Why is Linux so widespread?

• The career benefits of open-source contribution

• And much more!

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Timestamps

(00:00) Intro

(02:23) How widespread is Linux?

(06:00) The difference in complexity in different devices powered by Linux

(09:20) What is the Linux kernel?

(14:00) Why trust is so important with the Linux kernel development

(16:02) A walk-through of a kernel change

(23:20) How Linux kernel development cycles work

(29:55) The testing process at Kernel and Kernel CI

(31:55) A case for the open source development process

(35:44) Linux kernel branches: Stable vs. development

(38:32) Challenges of maintaining older Linux code

(40:30) How Linux handles bug fixes

(44:40) The range of work Linux kernel engineers do

(48:33) Greg’s review process and its parallels with Uber’s RFC process

(51:48) Linux kernel within companies like IBM

(53:52) Why Linux is so widespread

(56:50) How Linux Kernel Institute runs without product managers

(1:02:01) The pros and cons of using Rust in Linux kernel

(1:09:55) How LLMs are utilized in bug fixes and coding in Linux

(1:12:13) The value of contributing to the Linux kernel or any open-source project

(1:16:40) Rapid fire round

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The Pragmatic Engineer deepdives relevant for this episode:

What TPMs do and what software engineers can learn from them

The past and future of modern backend practices

Backstage: an open-source developer portal

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See the transcript and other references from the episode at ⁠⁠https://newsletter.pragmaticengineer.com/podcast⁠⁠

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