Systems guide
9 minConnection refused vs timed out vs no route to host
Diagnose connection refused, timeout, and no route to host errors from the terminal without mistaking one network symptom for a certain cause.
Read the guideDiagnose the system, not just the symptom
Practical terminal guides that explain what the system is doing.
Trace connection failures, read socket state, understand file descriptors, and choose safer command forms. Every systems guide connects observable terminal output to the mechanism underneath it.
12 systems troubleshooting guides3 stand-alone learning guides2 app walkthroughsReal product screenshots
Systems troubleshooting
Follow the evidence from command output to root cause
Systems guide
8 minHow to find the process listening on a port
Find which process owns a listening TCP port with ss or lsof on Linux and macOS, then verify the process safely before deciding what to change.
Read the guideSystems guide
9 minWhy localhost works on the host but not in Docker
Diagnose Docker localhost failures by checking container namespaces, bind addresses, published ports, and the correct route back to a host service.
Read the guideSystems guide
10 minHow to read TCP states in ss output
Read LISTEN, ESTAB, TIME-WAIT, and other TCP states in Linux ss output, then connect each socket to the local endpoint and process that owns it.
Read the guideSystems guide
10 minWhy a listening port can still be unreachable
Trace an unreachable service from its listening socket through bind scope, firewalls, containers, and cloud controls with safe terminal checks.
Read the guideSystems guide
10 minDNS resolves, but curl fails: what to check next
Trace a curl failure after DNS succeeds through address selection, routing, TCP, TLS, proxies, and HTTP without bypassing certificate checks.
Read the guideSystems guide
9 minHow to read curl verbose output
Read curl -v output as a connection timeline: DNS, address attempts, TLS, request and response headers, redirects, and connection reuse.
Read the guideSystems guide
11 minHow to make curl fail safely in shell scripts
Handle curl transport errors and HTTP failure statuses safely in shell scripts with bounded requests, --fail-with-body, and explicit status checks.
Read the guideSystems guide
9 minHow to diagnose “Too many open files” on Linux
Diagnose Linux file-descriptor exhaustion, distinguish per-process from system-wide limits, find leaks, and raise limits without hiding the cause.
Read the guideSystems guide
8 minWhy deleted files still use disk space on Linux
Learn why an unlinked Linux file can keep disk blocks allocated, find the process holding it open, and reclaim space without corrupting active services.
Read the guideSystems guide
9 minfind -exec vs xargs -0 for unusual filenames
Compare find -exec with xargs -0 for unusual Linux filenames, including batching, exit status, stdin, partial-record, race, and deletion tradeoffs.
Read the guideSystems guide
8 minWhy stderr bypasses pipes—and how to capture it
See why shell pipes carry stdout but leave stderr on the terminal, then merge, separate, and capture both streams without hiding command failures.
Read the guideLearn the command line
Useful with or without Terminaster
Learning guide
8 minHow to learn terminal commands without memorizing everything
Learn terminal commands through real tasks, safe practice, built-in help, and retrieval—not giant command lists. Includes a repeatable daily method.
Read the guideLearning guide
10 minA 14-day terminal practice plan for beginners
Build command-line confidence in 15 minutes a day with a safe two-week terminal practice plan covering files, search, pipes, processes, and review.
Read the guideLearning guide
9 minHow to read terminal commands: flags, arguments, pipes, and redirects
Learn how to read a terminal command from left to right by identifying the program, options, arguments, pipes, redirects, quoting, and placeholders.
Read the guideUse the app
Short Terminaster walkthroughs
App tutorial
6 minHow to save a terminal command in Terminaster
Save your first terminal command in Terminaster on Mac, add useful context, review the generated learning cards, and avoid saving secrets or brittle paths.
Read the guideApp tutorial
7 minHow to review terminal commands with spaced repetition
Use Terminaster review sessions to recall terminal commands, reveal answers, rate honestly, fix weak cards, and keep daily practice short.
Read the guideGo deeper
Learn the mental model behind the command
The free Concepts library covers 123 ideas—from paths, quoting, and streams to networking, concurrency, algorithms, reliability, and interactive graphics.