Linux Filesystems and Default Directories

Definition: The Virtual File System is a software layer in the Linux kernel that:

• Provides the filesystem interface to userspace programs

• Allows different filesystem implementations to coexist

• Acts as an abstraction layer between applications and physical storage

• Provide structured way to store data

• Determine file size limits and number of files

• Share common goal of storing/accessing data

• Implement different mechanisms and features

• Meet specific needs based on use case

• Standard framework adopted by most Linux distributions

• Provides consistent location for system-level files

• Allows reliability across different distributions

• Some variations exist between distros, but core structure remains

/ (Root Directory)

• Purpose: Base of entire Linux filesystem hierarchy

• Description: Starting point for all directories

• Note: Everything begins here

/home

• Purpose: Contains user home directories

• Description: Stores personal files and user-specific configurations

• Note: Not all users have home directories (depends on creation options)

/etc

• Purpose: System-wide configuration files

• Description: Controls operation of programs and system services

• Pronunciation: Often called "etsy"

• Note: Most application configuration files stored here

/usr/local

• Purpose: Locally installed software

• Description: Directory structure similar to root (/)

• Use: Where users/administrators install custom software

• Structure: Contains subdirectories like bin, lib, share, etc.

/opt

• Purpose: Add-on application software packages

• Description: Similar to /usr/local but without prebuilt directory structure

• Use: Reserved for optional software installations

• Difference: Less structured than /usr/local

/root

• Purpose: Home directory of root user

• Description: Super user's (administrator) personal directory

• Warning: Not to be confused with / (root directory)

• Contents: Root user's configuration files and data

/srv

• Purpose: Data for services provided by system

• Description: Service-specific data storage

• Common Use: HTML files for web servers

• Example: Web server document roots

1. VFS enables multiple filesystem types to work together

2. Common filesystems have different features for different needs

3. FHS provides standard directory structure across distributions

4. Directory hierarchy starts at / (root)

5. Each directory has specific purpose and convention

6. Configuration typically stored in /etc

7. User data typically in /home

8. Local software in /usr/local or /opt

A software layer in the Linux kernel that provides the filesystem interface to userspace programs and allows different filesystem implementations to coexist.

1. ext2/3/4 (extended filesystem)

2. XFS

3. btrfs (butterfs)

4. ZFS

A standard framework adopted by most Linux distributions that provides a consistent structure for storing system-level files across different distributions.

The root directory is the base starting point of the Linux filesystem hierarchy, represented by / (forward slash).

User home directories containing personal files and user-specific configuration data.

Stores system-wide configuration files that control the operation of programs and services.

• / = Root directory (base of filesystem)

• /root = Home directory of the root user (super user/administrator)

Contains locally installed software with a directory structure similar to the root directory. Used by users and administrators to install custom software.

Reserved for installation of add-on application software packages. Similar to /usr/local but without a prebuilt directory structure.

• /usr/local - Has prebuilt directory structure (bin, lib, etc.)

• /opt - No prebuilt structure, for optional add-on packages

Stores data for services provided by the system, commonly used for serving HTML files for web servers.

It allows different filesystem implementations (ext4, XFS, btrfs, ZFS, etc.) to coexist and provides a unified interface to userspace programs.

• Provide structured way to store data

• Determine file size and number limits

• Store and access data

• Meet specific needs through different features

In the /etc directory

No, it depends on the options used when the user account was created.

The super user or administrative account with full system privileges.

Serving HTML files for web servers or storing data for other system services.

Either /usr/local or /opt, depending on whether you need a structured directory layout.

ext2, ext3, and ext4

It provides a reliable, consistent framework for locating system files across different Linux distributions, though some variations exist.

1. Directory purposes:

   • / = root (base)

   • /home = user directories

   • /etc = configuration

   • /usr/local = local software (structured)

   • /opt = add-on software (unstructured)

   • /root = root user's home

   • /srv = service data

2. VFS concept:

   • Kernel layer

   • Enables multiple filesystems

   • Provides unified interface

3. Common filesystems:

   • ext2/3/4 (most common)

   • XFS, btrfs, ZFS

4. Key distinctions:

   • / vs /root

   • /usr/local vs /opt

   • /home vs /root

# Explore directories

ls /

ls /etc

ls /home

ls /usr/local

ls /opt

# Check filesystem type

df -T

mount | grep "^/"