Day 3: Skeleton of Linux and Basic Commands

Hello everyone.

In this post, I am going to write about the basic skeleton of a Linux system and some basic Linux commands. By skeleton, I mean the basic directory structure of Linux and why those directories exist.

Understanding this is very important, because in Linux everything is organized in a specific way, and once you understand this structure, Linux starts to make sense.

Linux Filesystem Skeleton

Linux follows a standard filesystem hierarchy.

Everything in Linux starts from the root directory, which is represented by /.

Unlike Windows, Linux does not have drives like C:, D:, etc. All files and directories are organized under /.

Important Directories and Their Purpose

/

This is the root of the filesystem. Every file and directory in Linux exists under this directory.

/bin

This directory contains essential binary executables.

These are basic commands required for the system to work, even in single-user mode.

Examples:

• ls
• cp
• mv
• rm
• cat

These commands are available for all users.

/sbin

This directory contains system binaries.

These are mostly administrative commands used by the root user.

Examples:

• ip
• mount
• reboot
• shutdown

Normal users usually do not need these commands.

/etc

This directory contains configuration files.

Almost every service or application stores its configuration here.

Examples:

• /etc/passwd — user information
• /etc/group — group information
• /etc/hostname — system hostname
• /etc/systemd/ — systemd configuration

In Linux, configuration is mostly done by editing text files.

/home

This directory contains home directories of users.

Each user has a separate directory inside /home.

Example:

• /home/kiran

User-specific files, downloads, documents, and settings are stored here.

/root

This is the home directory of the root user.

It is different from /home/root.

/var

This directory contains variable data.

These files change frequently while the system is running.

Examples:

• /var/log — system logs
• /var/cache — cache files
• /var/spool — print jobs, mail queues

/tmp

This directory contains temporary files.

Files here are usually deleted automatically after reboot.

Applications use this directory for temporary storage.

/usr

This directory contains user applications and libraries.

It includes:

• /usr/bin — user commands
• /usr/lib — libraries
• /usr/share — shared data

Most installed applications reside here.

/lib

This directory contains shared libraries required by binaries in /bin and /sbin.

Without these libraries, basic commands will not work.

/proc

This is a virtual filesystem, not a real directory on disk.

It provides information about:

• running processes
• kernel
• system memory
• CPU

Examples:

• /proc/cpuinfo
• /proc/meminfo

These files are generated by the kernel.

/dev

This directory contains device files.

In Linux, hardware devices are represented as files.

Examples:

• /dev/sda
• /dev/null
• /dev/tty

This follows the idea that everything in Linux is a file.

Basic Linux Commands

Now let us look at some basic commands that are used frequently.

pwd

Prints the present working directory.

pwd

ls

Lists files and directories.

ls
ls -l
ls -a

cd

Used to change directory.

cd /etc
cd ..
cd ~

mkdir

Creates a directory.

mkdir test
mkdir -p dir1/dir2

touch

Creates an empty file.

touch file.txt

cp

Copies files or directories.

cp file1 file2
cp -r dir1 dir2

mv

Moves or renames files.

mv file1 file2
mv file /tmp

rm

Deletes files or directories.

rm file
rm -r dir

This command is dangerous if used incorrectly.

cat

Displays file content.

cat file.txt

less

Used to view large files.

less file.txt

Press q to quit.

man

Displays the manual page of a command.

man ls

This is one of the most important commands.