cli

Command line

Start knowing only how to click. Finish able to navigate, search, and automate your system from a bare terminal prompt.

10 units·36 lessons·~13 h

The shell

A terminal is a window; a shell is the program inside it. Learn the prompt, type a command, and understand where you are in the filesystem.

01 What is a terminal? 15 min 02 The prompt and commands 18 min 03 Where am I? 20 min

Files and paths

Name any file two ways: absolute paths start at / and always work; relative paths start from where you are and are shorter. Create, copy, move, delete, and read files without a graphical file manager.

01 Absolute and relative paths 18 min 02 Making, copying, moving, and deleting 22 min 03 Reading files 18 min

Streams and pipes

Every process has three standard streams (stdin, stdout, stderr). Redirection rewires them to files; pipes connect stdout of one command to stdin of the next. Master these and you can compose any text-processing pipeline.

01 stdin, stdout, and stderr 18 min 02 Redirection 22 min 03 Pipes and grep 22 min 04 Counting and slicing 25 min

Finding things

Globs expand in the shell before any command runs. find searches a directory tree by name, type, size, or age. grep searches file contents with patterns. which, type, and command -v reveal how the shell locates commands.

01 Globs and wildcards 18 min 02 Finding files with find 22 min 03 Searching content with grep 20 min 04 Locating commands with which and type 16 min

Permissions and users

Every Linux file carries nine permission bits for user, group, and other. chmod sets them; chown wires the right owner and group; sudo lets you act as root for one command without abandoning least-privilege discipline.

01 rwx and chmod 22 min 02 Ownership and chown 20 min 03 sudo and root 22 min

Text processing

cut extracts columns, sort | uniq -c | sort -rn builds frequency tables, sed rewrites streams in-place, and awk handles field arithmetic and per-key summaries — four composable tools that cover 90% of structured log analysis without scripting languages.

01 cut and fields 20 min 02 sort and uniq 22 min 03 sed substitution 22 min 04 awk essentials 25 min

Processes and jobs

Every running program is a PID in a tree rooted at init. SIGTERM asks politely; SIGKILL cannot be caught and skips cleanup. Job control lets you suspend, background, and foreground work within a session — but nohup or disown is required to survive terminal closure. Load average and free -h tell you in seconds whether a machine is CPU-bound, I/O-bound, or memory-starved.

01 Processes and ps 20 min 02 Signals and kill 22 min 03 Jobs and backgrounding 22 min 04 Monitoring resources 22 min

Shell scripting

Variables without quotes trigger word splitting and glob expansion — the root of most script bugs. Every command exits with a code; $? and [[ ]] let you branch on success or failure. set -euo pipefail turns bash into a fail-fast interpreter; trap guarantees cleanup on any exit. Functions with local variables are the unit of reuse.

01 Variables and quoting 20 min 02 Conditionals and exit codes 22 min 03 Loops and arguments 22 min 04 Robust scripts 25 min

SSH and remote work

ssh user@host opens an encrypted shell; TOFU and ~/.ssh/config make it safe and ergonomic. Key authentication keeps the private key on the client and puts only the public key on the server. rsync transfers only changed bytes and mirrors directories cleanly — but --delete erases without confirmation, so --dry-run is mandatory. tmux decouples your terminal from the SSH connection so long-running tasks survive disconnects.

01 SSH basics 25 min 02 Key authentication 28 min 03 scp and rsync 28 min 04 tmux basics 25 min

Putting it together

Real CLI mastery means composing the individual tools into workflows: a find+grep+cut+sort+awk pipeline answers incident questions in seconds; a set -euo pipefail script with trap and functions automates maintenance safely; rsync+ssh+tmux ties deployment and long-running jobs into a disconnect-proof workflow.

01 Log analysis pipeline 30 min 02 A maintenance script 35 min 03 Remote ops capstone 35 min

Build with this track

Guided projects that exercise what you learn here.

◆ Projects

Homelab Secure Stack

Stand up a self-hosted media and home-server stack on nas01.example where five services share a single VPN container's network namespace — the kill-switch drops all traffic the moment the tunnel dies, a split-tunnel whitelist carves out LAN access, and three layered access rings (localhost / LAN 10.0.0.0/24 / mesh-VPN 100.64.0.30) keep the right doors open to the right people. Harden the host with SSH key-only auth, fail2ban, and unattended security upgrades; write a rotating, age-encrypted off-site backup; and walk away knowing the stack stays dark if anything breaks.

Next track

Linux, the operating system

You can drive the shell — now learn the system under it: how Linux boots, runs services, manages users and storage, and how to keep it alive when it breaks.