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Chapter 3.8 - Types of File Systems

Learning Objectives​

By the end of this chapter, you will be able to:

  • Understand the different types of file systems
  • Identify common file systems
  • Choose the right file system for the case
  • Understand special file systems

What is a File System?​

A file system defines how data is organized and stored on a disk. Linux supports many types of file systems.

Local File Systems​

ext4 (Fourth Extended)​

The most common on Linux:

Features:

  • Journaled: Crash-resistant
  • Max size: 1EB (exabyte)
  • Max file: 16TB
  • Stable and mature

Usage:

  • Default file system
  • Local disks
  • General-purpose servers

Commands:

# Create
mkfs.ext4 /dev/sda1

# Check
fsck.ext4 /dev/sda1

# View info
tune2fs -l /dev/sda1

xfs​

High performance for large files:

Features:

  • Very high performance for large files
  • Max size: 8EB
  • Max file: 8EB
  • Dynamic allocation

Usage:

  • Databases
  • Large files
  • High-performance servers

Commands:

# Create
mkfs.xfs /dev/sda1

# Check
xfs_repair /dev/sda1

# View info
xfs_info /dev/sda1

btrfs (B-Tree File System)​

Advanced features:

Features:

  • Snapshots: Instantaneous
  • Compression: Transparent
  • Copy-on-Write: Efficient
  • Integrated RAID

Usage:

  • Systems requiring snapshots
  • Backups
  • Development environments

Commands:

# Create
mkfs.btrfs /dev/sda1

# Create a snapshot
btrfs subvolume snapshot /mnt/data /mnt/data/snapshot1

# Compression
mount -o compress=zlib /dev/sda1 /mnt

Comparison​

FSMax SizeMax FileJournalUsage
ext41EB16TBYesGeneral
xfs8EB8EBYesLarge files
btrfs16EB16EBYesAdvanced

Network File Systems​

NFS (Network File System)​

File sharing over network:

# Server: Export
# /etc/exports
/home/user1 192.168.1.0/24(rw,sync)

# Client: Mount
mount -t nfs server:/home/user1 /mnt/nfs

Usage:

  • File sharing between Unix/Linux systems
  • Centralized file servers

CIFS/SMB​

Windows compatible:

# Mount a Windows share
mount -t cifs //server/share /mnt/smb -o username=user

Usage:

  • Cross-platform sharing
  • Windows compatibility

Special File Systems​

tmpfs​

In-memory (RAM):

# Mount tmpfs
mount -t tmpfs -o size=1G tmpfs /mnt/tmpfs

# Used for:
# - /tmp (often)
# - /dev/shm (shared memory)

Features:

  • Very fast (RAM)
  • Temporary (lost on reboot)
  • Size limited by RAM

procfs​

Interface to the kernel:

# Automatically mounted on /proc
# Contains:
# - /proc/cpuinfo: CPU info
# - /proc/meminfo: Memory info
# - /proc/pid/: Process details

Features:

  • Virtual file system
  • Real-time data
  • Read-only (generally)

sysfs​

System information:

# Automatically mounted on /sys
# Contains:
# - /sys/class/: Device classes
# - /sys/devices/: Devices

Features:

  • Hardware interface
  • Hardware configuration
  • Virtual

Management Commands​

View Mounted File Systems​

# Simple list
mount

# Human-readable format
df -h

# File system types
mount | grep -E '^/dev' | awk '{print $5}' | sort -u

Mount/Unmount​

# Mount
mount /dev/sda1 /mnt
mount -t ext4 /dev/sda1 /mnt

# Mount with options
mount -o rw,noexec /dev/sda1 /mnt

# Unmount
umount /mnt
umount /dev/sda1

# Force unmount (if busy)
umount -f /mnt
umount -l /mnt  # Lazy unmount

Permanent Configuration (/etc/fstab)​

# Format: device mountpoint fstype options dump pass
/dev/sda1  /          ext4    defaults        0 1
/dev/sda2  /home      ext4    defaults        0 2
/dev/sda3  /var       xfs     defaults        0 2
server:/export /mnt/nfs nfs   defaults        0 0

Common options:

  • defaults: rw, suid, dev, exec, auto, nouser, async
  • noexec: No execution
  • nosuid: Ignore SUID
  • ro: Read-only
  • noatime: No atime update

Verification and Repair​

fsck​

Check and repair:

# Check (without repair)
fsck /dev/sda1

# Automatically repair
fsck -a /dev/sda1

# Force check
fsck -f /dev/sda1

# Specific to ext4
fsck.ext4 /dev/sda1

Important:

  • Unmount before fsck (if possible)
  • Single-user mode for root system

Summary​

In this chapter, you learned:

Local types: ext4 (standard), xfs (large files), btrfs (advanced)
Network types: NFS (Unix), CIFS/SMB (Windows)
Special types: tmpfs (RAM), procfs (kernel), sysfs (system)
Management: mount, umount, /etc/fstab for permanent mounting
Verification: fsck to repair file systems

Next Steps​

Lab 3.4: Complete Practice
Module 4: Process Management

Chapter created on: December 2024