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🚀 Expert Tier

Levels 5–6 · Goal: building and mastery · ~10–16 weeks at 45–60 minutes a day

You understand Linux and can run it. Now you'll build software that works with the kernel, and master the technologies that power modern infrastructure: containers, virtualization, performance tooling, security, and automation.

What you'll be able to do

  • Watch any program talk to the kernel with strace, and reason in system calls and file descriptors.
  • Write network servers that handle many clients, shut down cleanly, and run as hardened systemd services.
  • Compile, link, package, and debug native code with gcc, make, gdb, and core dumps.
  • Build a container from raw namespaces and cgroups, and explain exactly what Docker adds on top.
  • Find performance bottlenecks with perf, flame graphs, and eBPF.
  • Harden a system with capabilities, AppArmor, and auditing, and automate it all with Ansible.

The levels

  • Level 5: Building for Linux

    System calls, file descriptors, processes and signals in code, pipes and sockets, services, building software, and debugging.

    Start Level 5

  • Level 6: Expert topics

    Containers from scratch, performance, security, the kernel, advanced networking, virtualization, Docker and Podman, and Ansible.

    Start Level 6

Tier checkpoint

You've mastered this handbook when you can do all of these without notes:

  • Explain, using strace output, every syscall cat file.txt makes.
  • Explain why a container is "just a process", and name each kernel feature that isolates it.
  • Find the hottest function in a CPU-bound program with perf and a flame graph.
  • Debug a segfault from a core dump with gdb.
  • Rebuild your Level 4 server with a single ansible-playbook run.

See the full roadmap for every concept in this tier. For what to study next, see the "Where to go next" section in the Level 6 overview.