Study guide · Topic overview
A subject-based path for the Linux command line: how the shell works, how files and permissions fit together, and which command to reach for when you need to search, install, start a service, or check a disk.
Scope notice: Linux CLI Fundamentals is an independent study topic, not CompTIA Linux+, LPIC-1, or RHCSA. The domains below organize everyday command-line skills. Items tagged Extra sit outside that everyday set. These pages do not include a terminal simulator; practice on a real shell.
The Linux command line is the text interface to the operating system. You type a command, the shell interprets it, and a program runs. This path focuses on the skills used every day on servers, developer workstations, and virtual machines: moving around the file system, reading and editing text, controlling who can change a file, watching processes, installing packages, talking to the network, and diagnosing a full disk or a failed service.
It is vendor-neutral in the sense that the same commands appear on Debian, Ubuntu, Fedora, and RHEL-family systems. Where families differ, the notes name both tools, such as apt versus dnf, instead of pretending there is only one package manager.
These weights organize the notes, flashcards, and 200 practice questions. They are not official exam weights.
How the shell finds programs and how you move around the tree.
Nodn., .., and ~pwd, cd, ls, tab completion, and command historyPATH, which, type, and manCreate, copy, search, and connect commands together.
cp, mv, rm, mkdir, ln, and findcat, less, head, tail, grep, and nano>, >>, and 2> redirectiontar and gzipWho can read a file, and what is running right now.
chmod octal math (755, 644, 700) and chownsudo vs. su, /etc/passwd, and /etc/shadowps, top, kill, and background jobsInstall software, start services, and test connectivity.
apt on Debian/Ubuntu and dnf on Fedora/RHELsystemctl start, stop, enable, and statusip, ss, ping, dig, curl, and sship and ss over legacy ifconfig and netstatFind space problems, failed mounts, and the right log.
df -h vs. du -sh, lsblk, mount, and /etc/fstabjournalctl, dmesg, and /var/logfsck only on an unmounted file systemLinux uses one tree. Knowing where configuration, logs, and home directories live saves time.
| Path | What belongs there |
|---|---|
/ | The root of the file system. Every other path hangs from here. |
/home | User home directories, such as /home/ada. Root's home is /root. |
/etc | System configuration: passwd, fstab, hosts, and service files. |
/var | Data that changes while the system runs, including /var/log and caches. |
/tmp | Shared temporary files. Often cleared on reboot. The sticky bit is common here. |
/usr | Most installed programs and shared libraries (/usr/bin, /usr/lib). |
/bin, /sbin | Essential user and administrator commands. On modern systems these are often links into /usr. |
/opt | Optional third-party software installed outside the distribution packages. |
/proc, /dev | Kernel and process information, and device nodes such as disks and terminals. |
Learn what each command solves, not only its name. The same facts appear in the core notes and flashcards. They also match the Linux command list used in the CompTIA A+ Linux notes.
| Job | Commands |
|---|---|
| Move and list | pwd cd ls -l man |
| Create and change files | cp mv rm mkdir touch ln -s nano |
| Read and search | cat less head tail grep find |
| Permissions | chmod chown sudo su |
| Processes | ps aux top kill |
| Packages | apt (Debian/Ubuntu) dnf (Fedora/RHEL) |
| Services and logs | systemctl journalctl |
| Network | ip ss ping dig curl traceroute ssh |
| Disks | df -h du -sh lsblk mount fsck |
Key files: /etc/passwd stores user accounts, /etc/shadow stores password hashes, /etc/hosts maps names to IPs locally, /etc/fstab defines file systems mounted at boot, and /etc/resolv.conf lists DNS servers.
Typing on a real shell is the point of this topic.
Use a Linux virtual machine, a cloud instance you can rebuild, or Windows Subsystem for Linux. Avoid practicing destructive commands such as rm -rf or fsck on a machine you cannot restore.
When a command fails, read the exact message. command not found is a PATH or package problem. Permission denied is ownership or mode. Then run man command and jump to the EXAMPLES section.
Connect two tools before you memorize flags in isolation: ps aux | grep ssh, du -sh * | sort -h, or journalctl -u ssh | tail. Pipes are how daily work actually looks.
A practical sequence that works if you are new to the terminal.
Practice pwd, cd, and ls -l until absolute and relative paths feel automatic. Open /etc, /var/log, and your home directory on purpose.
Use less, head, tail, and grep on log files. Add pipes and redirection only after you can find text without them.
Memorize read = 4, write = 2, execute = 1, then explain 755, 644, and 700 out loud. Practice chmod and chown on files you created.
On a disposable VM, install a package with apt or dnf, then use systemctl status and journalctl to see whether it is running.
Use the flashcards for PATH, permissions, sudo vs. su, df vs. du, and the five key files in /etc.
Work through original questions, review every explanation, and return to the notes on domains below 75%.
The overview, core notes, flashcards, and practice exams are all published.
Scope, domains, command map, file-system layout, and a study plan for everyday Linux CLI.
Technical reference notes for the shell, files, permissions, packages, services, and networking.
40 recall cards in four decks, plus memory notes for commands and paths.
200 original questions with custom exams, explanations, and a score report by domain.
No. This is a subject-based learning path for everyday Linux command-line skills. It is not CompTIA Linux+, LPIC-1, or RHCSA, and it does not award a credential.
The notes cover commands that work on common GNU/Linux systems. Package examples use apt on Debian and Ubuntu, and dnf on Fedora and RHEL-family systems. Service examples use systemd.
A virtual machine, a cloud instance, or Windows Subsystem for Linux is enough. The pages do not include a command-line simulator, so type the commands on a real shell.
Items tagged Extra are useful on the job but sit outside the everyday command set this path emphasizes, such as legacy tools like ifconfig and netstat.
Scores are unofficial percentages. There is no scaled 100–900 score because this is not a named certification exam. Domains below 75% are marked as focus areas.
Command flags and default paths can differ by distribution and version. Confirm behavior with man on the system you are using.
Useful companions while you study.
Generate strong random passwords with custom length, characters, symbols, and security options.
Encode text and files to Base64 or decode Base64 data with UTF-8 support.
Convert structured data between JSON and YAML with formatting and validation.
Compare two text blocks and highlight added, removed, and changed content.
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