Linux Disk and File Systems Management Guide

Disk and filesystem management is crucial for Linux system administration. This guide covers partitioning, formatting, mounting, and managing storage devices.

Overview: Disk Management Tools

Tool	Purpose	Example
`fdisk`	Partition disks (MBR/GPT)	`fdisk /dev/sda`
`parted`	Advanced partitioning	`parted /dev/sda`
`mkfs`	Create filesystems	`mkfs.ext4 /dev/sda1`
`mount`	Mount filesystems	`mount /dev/sda1 /mnt`
`umount`	Unmount filesystems	`umount /mnt`
`df`	Disk space usage	`df -h`
`du`	Directory space usage	`du -sh /var`
`lsblk`	List block devices	`lsblk`
`blkid`	Block device attributes	`blkid /dev/sda1`

Viewing Disk Information

List Block Devices

# List all block devices
lsblk

# Show filesystem info
lsblk -f

# Show size in bytes
lsblk -b

# Show specific device
lsblk /dev/sda

# Tree view with detailed info
lsblk -a

Device Information

# Show UUID and filesystem
sudo blkid

# Specific device
sudo blkid /dev/sda1

# Show disk details
sudo fdisk -l

# Specific disk
sudo fdisk -l /dev/sda

# Detailed SMART info
sudo smartctl -a /dev/sda  # Requires smartmontools

Disk Partitioning

fdisk - MBR/GPT Partitioning

# Start fdisk
sudo fdisk /dev/sda

# Interactive commands:
# m - Show help
# p - Print partition table
# n - Create new partition
# d - Delete partition
# t - Change partition type
# w - Write changes and exit
# q - Quit without saving

Creating Partitions with fdisk

sudo fdisk /dev/sdb

# Example session:
Welcome to fdisk (util-linux 2.36.1).
Command (m for help): n
Partition type
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-..., default 2048): [Enter]
Last sector, +sectors or +size{K,M,G,T,P} ...: +10G

Command (m for help): w
The partition table has been altered.

parted - Advanced Partitioning

# Interactive mode
sudo parted /dev/sda

# Create GPT partition table
sudo parted /dev/sda mklabel gpt

# Create partition
sudo parted /dev/sda mkpart primary ext4 0% 100%

# Delete partition
sudo parted /dev/sda rm 1

# Print partition table
sudo parted /dev/sda print

# Resize partition
sudo parted /dev/sda resizepart 1 50GB

# Set boot flag
sudo parted /dev/sda set 1 boot on

Creating Filesystems

mkfs - Make Filesystem

# ext4 filesystem
sudo mkfs.ext4 /dev/sdb1

# ext4 with label
sudo mkfs.ext4 -L "MyData" /dev/sdb1

# XFS filesystem
sudo mkfs.xfs /dev/sdb1

# Btrfs filesystem
sudo mkfs.btrfs /dev/sdb1

# FAT32 filesystem
sudo mkfs.vfat -F 32 /dev/sdb1

# NTFS filesystem
sudo mkfs.ntfs /dev/sdb1

# Swap partition
sudo mkswap /dev/sdb2

Filesystem Options

# ext4 with custom options
sudo mkfs.ext4 -b 4096 -L DataDisk /dev/sdb1

# XFS with specific sector size
sudo mkfs.xfs -f -s size=4096 /dev/sdb1

# Create with reserved blocks
sudo mkfs.ext4 -m 1 /dev/sdb1  # 1% reserved for root

Mounting Filesystems

Basic Mounting

# Mount filesystem
sudo mount /dev/sdb1 /mnt/data

# Mount with specific filesystem type
sudo mount -t ext4 /dev/sdb1 /mnt/data

# Mount read-only
sudo mount -o ro /dev/sdb1 /mnt/data

# Remount with different options
sudo mount -o remount,rw /mnt/data

# Unmount filesystem
sudo umount /mnt/data

# Force unmount
sudo umount -f /mnt/data

# Lazy unmount
sudo umount -l /mnt/data

Mount Options

# Common options
sudo mount -o rw,nosuid,nodev /dev/sdb1 /mnt/data

# Options:
# rw - Read-write
# ro - Read-only
# noexec - Prevent execution
# nosuid - Ignore SUID bits
# nodev - Ignore device files
# defaults - rw,suid,dev,exec,auto,nouser,async

Permanent Mounts - /etc/fstab

# Edit fstab
sudo nano /etc/fstab

# Format: device mountpoint filesystem options dump pass
/dev/sdb1  /mnt/data  ext4  defaults  0  2

# Using UUID (recommended)
UUID=xxxx-xxxx  /mnt/data  ext4  defaults  0  2

# Test fstab without rebooting
sudo mount -a

# Find UUID
sudo blkid /dev/sdb1

Auto-mounting USB Drives

# Mount using UUID
UUID=1234-5678  /media/usb  vfat  defaults,nofail,x-systemd.device-timeout=1  0  0

# Create mount point
sudo mkdir -p /media/usb

# Test mount
sudo mount /media/usb

Disk Space Management

df - Disk Free Space

# Show disk usage
df -h

# Show inodes
df -i

# Specific filesystem type
df -t ext4

# Exclude type
df -x tmpfs

# Show all filesystems
df -a

# Show total
df -h --total

du - Disk Usage

# Directory size
du -sh /var/log

# Top-level directories
du -h --max-depth=1 /var

# All subdirectories
du -ah /home/user

# Sort by size
du -h /var | sort -rh | head -10

# Exclude patterns
du -h --exclude="*.log" /var

# Summary with total
du -ch /var/log | tail -1

# Human-readable with apparent size
du -sh * | sort -rh

Finding Large Files and Directories

# Top 10 largest directories
du -h / | sort -rh | head -10

# Find files larger than 100MB
sudo find / -type f -size +100M -exec ls -lh {} \; | awk '{print $9 ": " $5}'

# Largest files in current directory
du -a | sort -n -r | head -n 10

# Using ncdu (interactive)
ncdu /

# Disk usage by file type
find /var -name "*.log" -exec du -ch {} + | tail -1

LVM - Logical Volume Management

LVM Concepts

Physical Volume (PV) - Physical disk or partition
Volume Group (VG) - Pool of PVs
Logical Volume (LV) - Virtual partition from VG

Creating LVM Structure

# Create physical volume
sudo pvcreate /dev/sdb1

# Create volume group
sudo vgcreate myvg /dev/sdb1

# Create logical volume
sudo lvcreate -L 10G -n mylv myvg

# Format logical volume
sudo mkfs.ext4 /dev/myvg/mylv

# Mount logical volume
sudo mount /dev/myvg/mylv /mnt/data

Managing LVM

# Display information
sudo pvdisplay
sudo vgdisplay
sudo lvdisplay

# Extend volume group
sudo vgextend myvg /dev/sdc1

# Extend logical volume
sudo lvextend -L +5G /dev/myvg/mylv
sudo resize2fs /dev/myvg/mylv  # Resize filesystem

# Reduce logical volume (careful!)
sudo umount /dev/myvg/mylv
sudo e2fsck -f /dev/myvg/mylv
sudo resize2fs /dev/myvg/mylv 5G
sudo lvreduce -L 5G /dev/myvg/mylv

Swap Management

Creating Swap

# Create swap partition
sudo mkswap /dev/sdb2

# Enable swap
sudo swapon /dev/sdb2

# Create swap file
sudo fallocate -l 2G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

# Make permanent in /etc/fstab
/swapfile  none  swap  sw  0  0

Managing Swap

# Show swap usage
swapon --show
free -h

# Disable swap
sudo swapoff /dev/sdb2
sudo swapoff /swapfile

# Set swap priority
sudo swapon --priority 10 /swapfile

# Swappiness (how aggressively to use swap)
cat /proc/sys/vm/swappiness
sudo sysctl vm.swappiness=10  # Lower = less swap usage

Filesystem Maintenance

Checking Filesystems

# Check ext4 filesystem (unmounted!)
sudo umount /dev/sdb1
sudo fsck /dev/sdb1

# Force check
sudo fsck -f /dev/sdb1

# Check and repair automatically
sudo fsck -y /dev/sdb1

# Check without fixing
sudo fsck -n /dev/sdb1

# XFS check
sudo umount /dev/sdb1
sudo xfs_repair /dev/sdb1

Tuning Filesystems

# ext4 tuning
sudo tune2fs -l /dev/sdb1  # Show parameters

# Set reserved blocks to 1%
sudo tune2fs -m 1 /dev/sdb1

# Set label
sudo tune2fs -L "MyLabel" /dev/sdb1

# Set max mount count before check
sudo tune2fs -c 30 /dev/sdb1

# Disable journaling (not recommended)
sudo tune2fs -O ^has_journal /dev/sdb1

RAID Management

Software RAID with mdadm

# Create RAID 1 (mirror)
sudo mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1

# Create RAID 5
sudo mdadm --create /dev/md0 --level=5 --raid-devices=3 /dev/sdb1 /dev/sdc1 /dev/sdd1

# Check RAID status
sudo mdadm --detail /dev/md0

# Add spare drive
sudo mdadm --add /dev/md0 /dev/sde1

# Remove failed drive
sudo mdadm --fail /dev/md0 /dev/sdc1
sudo mdadm --remove /dev/md0 /dev/sdc1

# Save RAID configuration
sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf

Disk Performance Monitoring

I/O Statistics

# Install sysstat
sudo apt install sysstat

# Monitor disk I/O
iostat -x 2

# Per-device statistics
iostat -dx sda 2

# I/O per process
sudo iotop

Quick Reference

# View disks
lsblk                     # List block devices
sudo fdisk -l             # List partitions
sudo blkid                # Show UUIDs

# Partition
sudo fdisk /dev/sda       # Partition disk
sudo parted /dev/sda      # Advanced partitioning

# Format
sudo mkfs.ext4 /dev/sda1  # Create ext4
sudo mkswap /dev/sda2     # Create swap

# Mount
sudo mount /dev/sda1 /mnt # Mount filesystem
sudo umount /mnt          # Unmount

# Space usage
df -h                     # Disk free space
du -sh /path              # Directory size

# LVM
sudo pvcreate /dev/sdb1   # Create PV
sudo vgcreate vg /dev/sdb1 # Create VG
sudo lvcreate -L 10G -n lv vg # Create LV

# Maintenance
sudo fsck /dev/sda1       # Check filesystem
sudo e2fsck -f /dev/sda1  # Force check ext4