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A way into the notebook.
You don’t have to read everything in date order. Pick a question, start with the longer explanation, and follow the notes that interest you.
Path 01 · 4 reads
A service has failed. Where next?
Start with a longer walkthrough, then keep a few focused debugging notes close by.
- Start here
Debugging a systemd service without guessing
A complete walkthrough of the evidence a failed service leaves behind.
Article · 9 min read - Go deeper
Core dumps are free until you need one
The companion note for investigating a crash.
Short note - Keep handy
Find and kill the process using a TCP port
A quick reference for a port that is already in use.
Short note - Keep handy
Deleted files can still fill a disk
For the puzzling case where disk-space reports disagree.
Short note
Path 02 · 4 reads
Make sense of the numbers.
Read the explanation first, then explore the shorter notes on measurement and limits.
- Start here
Linux load average is not CPU usage
The longer read on load average and what to investigate next.
Article · 8 min read - Go deeper
perf counts, perf samples — pick the right one
A focused note on choosing a useful perf measurement.
Short note - Go deeper
MemoryHigh is a slope, MemoryMax is a cliff
A companion reference on memory limits.
Short note - Keep handy
Why is boot slow? Ask for the critical chain
A short detour into boot-time investigation.
Short note
Path 03 · 3 reads
Write scripts you can live with.
Small conventions and shell details that are worth revisiting before the next piece of automation.
- Start here
Write boring shell scripts
The full guide to predictable, maintainable shell automation.
Article · 7 min read - Keep handy
Print a value in reusable shell quoting
A small shell feature worth keeping in your notebook.
Short note - Keep handy
Stop grep matching itself without grep -v grep
The explanation behind a familiar process-search trick.
Short note
Path 04 · 3 reads
Look a little closer at the system.
For readers who enjoy the details behind familiar operating systems and tools.
- Start here
FreeBSD, NetBSD, OpenBSD and DragonFlyBSD: what actually differs
The long-form comparison of the BSD family.
Article · 8 min read - Explore next
ldd may run the binary you are inspecting
A closer look at a command that deserves some care.
Short note - Keep handy
Ask the package manager what changed on disk
A short reference for checking installed files.
Short note
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