Linux · Networking · Command line
Small notes.
Clearer systems.
Working notes on the details that make everyday systems easier to understand: what a queue measures, when a task runs, and what a diagnostic command actually tells you.
The notebook
04 notes- 01
Networking
Reading TCP buffers on Linux
Understand queue sizes, receive windows, and why a larger buffer is not always the right fix.
Read queue measurements in context, estimate the bandwidth delay product, and distinguish application backpressure from limits imposed by the network. The note starts with observation before considering any system setting.
- 02
Linux
Scheduling work with systemd timers
Pair a timer with a service, choose a clock, and inspect what actually ran.
Follow the relationship between a timer and its service. Compare calendar schedules with elapsed intervals, understand missed runs, and use the journal to verify the outcome of scheduled work.
- 03
Command line
A methodical curl debugging session
Separate connection failures, HTTP responses, and timing with a few focused curl options.
Build a repeatable request against a local HTTP service. Separate headers from the response body, interpret exit status, and collect timing information without changing several variables at once.
- 04
Networking
Socket options with clear boundaries
Use address reuse, keepalive, and TCP_NODELAY for specific problems, with explicit checks.
Compare address reuse, idle connection checks, and small-write behavior. Each option solves a different problem, and effective values deserve the same attention as the values requested by the application.
A practical starting point
Begin with the symptom you can reproduce. A transfer that stalls, a timer that appears quiet, and a request that returns an unexpected status each call for a different observation. These notes keep that first observation close to the command or setting being discussed.
The emphasis is on ordinary Linux systems and tools that are useful at a terminal. Commands are deliberately short enough to inspect before running. Where a result depends on the operating system, the relevant assumption is stated in the text. Local manual pages remain the best guide to the exact version installed on a machine.
Read a note from the beginning when the topic is unfamiliar, or return to a section when you need to check a particular distinction. Related reading connects the networking notes, while the complete list above stays small enough to scan without a search box. For the editorial approach and scope, see about this notebook.