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Advanced Linux internals & tooling

Not a hardening course. It explains how Linux works underneath and how to find a bottleneck from the symptom: a method for performance problems, /proc and /sys, process lifecycle and the scheduler, boot and systemd internals, virtual memory and the OOM killer, cgroups and namespaces, the VFS, filesystems and the block layer, the network stack and name resolution, then strace, perf, flame graphs, eBPF tools and debuggers, and tuning only after measuring. Commands were run on Ubuntu Server 26.04 LTS (kernel 7.0) with RHEL 10 (kernel 6.12) differences noted. Twenty-one lessons across six sections, each with a self-test, and a final exam.

Advanced6 sections · 21 lessons · ~9h total · 52-question self-test

01

Method and processes

5 lessonsTest yourself

01A method for performance problemsUSE, workload characterisation and the first minute.16 min 02/proc and /sys: the kernel's own viewPer-process status, stack, io and memory maps.14 min 03Processes: fork, exec, wait and signalsHow processes are born, run and die.16 min 04The CPU schedulerEEVDF, priorities, real-time and run-queue latency.16 min 05CPU saturation: load, run queue and pressureLoad average, vmstat, mpstat and PSI.14 min

02

Boot and systemd

2 lessonsTest yourself

01Boot: firmware, boot loader, kernel and initramfsFrom power-on to systemd, and timing it.16 min 02systemd units and the dependency graphOrdering, requirements, jobs and generators.16 min

03

Memory and resource control

3 lessonsTest yourself

01Virtual memory, page cache and the OOM killerRSS vs PSS, reclaim, swap and OOM.18 min 02cgroup v2 resource control through systemdCPU, memory, IO and task limits on units.16 min 03Namespaces and cgroups by handunshare, nsenter and raw cgroup files.16 min

04

Files and storage

4 lessonsTest yourself

01Files, descriptors and the VFSfd tables, open files, inodes and limits.14 min 02Filesystem internals: ext4 and XFSInodes, extents, journaling and repair.16 min 03The block layer, device-mapper and LVMThe I/O path down to the disk, with LVM.16 min 04Disk I/O: latency, queues and saturationiostat, pidstat -d and biolatency.14 min

05

Networking

2 lessonsTest yourself

01The network stack, sockets and name resolutionPacket path, queues, drops and the DNS path.18 min 02Network troubleshooting: sockets, drops and packetsss, nstat, ip -s, tcpdump, mtr and iperf3.16 min

06

Tracing, profiling and tuning

5 lessonsTest yourself

01System calls and straceWhat a program asks the kernel, and its cost.14 min 02perf: sampling, flame graphs and off-CPU timeProfile CPU use and read a flame graph.16 min 03eBPF tools: bcc and bpftraceReady-made tools and one-liners in production.16 min 04Process debugging: ptrace, gdb and core dumpsAttach, inspect and capture a crash.14 min 05Tuning the kernel, after you have measuredMeasure, change one thing, verify.14 min

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Quick reference

Linux command cheat sheetCheat sheet Linux interview questionsInterview guide

Final exam

Test yourself on everything

52 questions drawn from all 6 sections — every answer explained as you pick.

Start final exam