LINUX FUNDAMENTALS
Study Notes • Core Concepts • Commands • Short Questions • MCQs
1. What Is Linux?
Linux is an open-source, Unix-like operating system family built around the Linux kernel. Linux is used in servers, personal
computers, cloud systems, embedded devices, and more. A distribution combines the kernel with system utilities, package
tools, and applications.
2. Main Components
Kernel: Manages hardware, memory, processes, and devices.
Shell: Provides a command-line interface.
File system: Organizes files and directories.
Utilities: Tools for searching, copying, monitoring, and managing a system.
Package manager: Installs and updates software.
3. Common Directories
/ Root of the directory tree.
/home User home directories.
/etc System configuration files.
/var Variable data such as logs.
/tmp Temporary files.
/usr Many user-space programs and shared resources.
4. Essential Commands
pwd — show current directory.
ls — list files and directories.
cd folder — change directory.
mkdir name — create a directory.
touch file.txt — create an empty file or update its timestamp.
cp source destination — copy files.
mv source destination — move or rename files.
cat file.txt — display file contents.
grep word file.txt — search text for a pattern.
man command — read a command manual.
5. Users and Permissions
Linux permissions commonly apply to owner, group, and others. Basic permissions are read (r), write (w), and execute (x).
Use only the access needed. Be careful with sudo because elevated privileges can change important system settings.
6. Processes and Services
ps — display process information.
top — view processes and resource use.
kill PID — request termination of a process; use carefully.
systemctl status service — check a service on systems using systemd.
A process is a running program; a service commonly runs in the background to provide a system function.
7. Packages and Updates
Package managers install, update, and remove software. Debian-based systems commonly use apt; Fedora-based
systems commonly use dnf. Prefer trusted repositories and install security updates. Commands vary by distribution.
8. Networking Basics
ip addr — view network interface addresses.
ping host — test basic reachability when permitted.
ss -tuln — show listening sockets on many Linux systems.
9. Short Questions and Answers
Linux Fundamentals Study Notes Page 1
Study Notes • Core Concepts • Commands • Short Questions • MCQs
1. What Is Linux?
Linux is an open-source, Unix-like operating system family built around the Linux kernel. Linux is used in servers, personal
computers, cloud systems, embedded devices, and more. A distribution combines the kernel with system utilities, package
tools, and applications.
2. Main Components
Kernel: Manages hardware, memory, processes, and devices.
Shell: Provides a command-line interface.
File system: Organizes files and directories.
Utilities: Tools for searching, copying, monitoring, and managing a system.
Package manager: Installs and updates software.
3. Common Directories
/ Root of the directory tree.
/home User home directories.
/etc System configuration files.
/var Variable data such as logs.
/tmp Temporary files.
/usr Many user-space programs and shared resources.
4. Essential Commands
pwd — show current directory.
ls — list files and directories.
cd folder — change directory.
mkdir name — create a directory.
touch file.txt — create an empty file or update its timestamp.
cp source destination — copy files.
mv source destination — move or rename files.
cat file.txt — display file contents.
grep word file.txt — search text for a pattern.
man command — read a command manual.
5. Users and Permissions
Linux permissions commonly apply to owner, group, and others. Basic permissions are read (r), write (w), and execute (x).
Use only the access needed. Be careful with sudo because elevated privileges can change important system settings.
6. Processes and Services
ps — display process information.
top — view processes and resource use.
kill PID — request termination of a process; use carefully.
systemctl status service — check a service on systems using systemd.
A process is a running program; a service commonly runs in the background to provide a system function.
7. Packages and Updates
Package managers install, update, and remove software. Debian-based systems commonly use apt; Fedora-based
systems commonly use dnf. Prefer trusted repositories and install security updates. Commands vary by distribution.
8. Networking Basics
ip addr — view network interface addresses.
ping host — test basic reachability when permitted.
ss -tuln — show listening sockets on many Linux systems.
9. Short Questions and Answers
Linux Fundamentals Study Notes Page 1
