gdisk Command Linux: Complete Guide to GPT Partition Table Management

The gdisk command is a powerful GPT (GUID Partition Table) partition editor for Linux systems that provides advanced capabilities for managing modern disk partitions. Unlike traditional MBR (Master Boot Record) partitioning tools, gdisk is specifically designed to work with GPT partition tables, supporting larger disks, more partitions, and enhanced data integrity features.

Understanding GPT vs MBR

Before diving into gdisk usage, it’s essential to understand the key differences between GPT and MBR partition schemes:

• Partition Limits: MBR supports only 4 primary partitions, while GPT supports up to 128 partitions by default
• Disk Size: MBR is limited to 2TB disks, GPT supports disks up to 9.4 ZB
• Data Integrity: GPT includes CRC32 checksums for error detection and recovery
• UEFI Compatibility: GPT is required for UEFI boot systems

Installing gdisk

Most modern Linux distributions include gdisk by default. If not installed, you can install it using your package manager:

# Ubuntu/Debian
sudo apt update && sudo apt install gdisk

# CentOS/RHEL/Fedora
sudo yum install gdisk
# or
sudo dnf install gdisk

# Arch Linux
sudo pacman -S gptfdisk

Basic gdisk Syntax and Options

The basic syntax for gdisk is:

gdisk [options] device

Common Options

• -l – List partition tables for all devices
• -t – Display all known partition type codes
• -v – Display version information
• -z – Zap (destroy) GPT data structures

Viewing Partition Information

List All Partition Tables

To view partition information for all available devices:

sudo gdisk -l

Sample Output:

GPT fdisk (gdisk) version 1.0.8

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.
Disk /dev/sda: 41943040 sectors, 20.0 GiB
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): A1B2C3D4-E5F6-7890-ABCD-1234567890AB
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 41943006
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048         1050623   512.0 MiB   EF00  EFI System Partition
   2         1050624        41943006   19.5 GiB    8300  Linux filesystem

View Specific Device Information

To examine a specific device:

sudo gdisk -l /dev/sda

Interactive gdisk Mode

The real power of gdisk lies in its interactive mode. Launch it by specifying a device:

sudo gdisk /dev/sda

This opens the gdisk interactive prompt:

GPT fdisk (gdisk) version 1.0.8

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help):

Essential Interactive Commands

Creating Partitions with gdisk

Step-by-Step Partition Creation

Let’s create a new partition on an empty disk:

sudo gdisk /dev/sdb

Command (? for help): n
Partition number (1-128, default 1): 1
First sector (2048-20971486, default = 2048): 
Last sector (2048-20971486, default = 20971486): +5G
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300): 
Changed type of partition to 'Linux filesystem'

Command (? for help): p
Disk /dev/sdb: 20971520 sectors, 10.0 GiB
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): F1E2D3C4-B5A6-9780-1234-567890ABCDEF
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 20971486
Partitions will be aligned on 2048-sector boundaries
Total free space is 10485693 sectors (5.0 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048        10487807   5.0 GiB     8300  Linux filesystem

Creating Multiple Partitions

Create additional partitions for a complete setup:

# Create swap partition
Command (? for help): n
Partition number (2-128, default 2): 2
First sector (10487808-20971486, default = 10487808): 
Last sector (10487808-20971486, default = 20971486): +1G
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300): 8200
Changed type of partition to 'Linux swap'

# Create data partition
Command (? for help): n
Partition number (3-128, default 3): 3
First sector (12584960-20971486, default = 12584960): 
Last sector (12584960-20971486, default = 20971486): 
Current type is 8300 (Linux filesystem)
Hex code or GUID (L to show codes, Enter = 8300): 
Changed type of partition to 'Linux filesystem'

Partition Type Codes

gdisk uses hexadecimal codes to identify partition types. Common codes include:

• EF00 – EFI System Partition
• 8300 – Linux filesystem
• 8200 – Linux swap
• 8301 – Linux reserved
• 8302 – Linux /home
• FD00 – Linux RAID
• 8E00 – Linux LVM

To view all available type codes:

Command (? for help): L

Advanced gdisk Operations

Changing Partition Names

Assign descriptive names to partitions:

Command (? for help): c
Partition number (1-3): 1
Enter name: Root Filesystem

Command (? for help): c
Partition number (1-3): 2
Enter name: Swap Space

Command (? for help): c
Partition number (1-3): 3
Enter name: Data Storage

Verifying Disk Integrity

Check for partition table errors:

Command (? for help): v

No problems found. 2014 free sectors (1007.0 KiB) available in 1
segments, the largest of which is 2014 (1007.0 KiB) in size.

Backup and Recovery

Create a backup of the partition table:

Command (? for help): b
Enter backup filename to save: /home/user/gpt-backup.bin
The backup GPT and MBR have been saved to /home/user/gpt-backup.bin.

Load a backup:

Command (? for help): l
Enter backup filename to load: /home/user/gpt-backup.bin
The backup GPT and MBR have been loaded.

Converting Between MBR and GPT

Convert MBR to GPT

gdisk can convert MBR partition tables to GPT while preserving data:

sudo gdisk /dev/sda

GPT fdisk (gdisk) version 1.0.8

Partition table scan:
  MBR: MBR only
  BSD: not present
  APM: not present
  GPT: not present

Found valid MBR and corrupt GPT. Which do you want to use?
 1 - MBR
 2 - GPT
 3 - Create blank GPT

Your answer: 2

Command (? for help): w

Expert Menu Options

Access advanced features through the expert menu:

Command (? for help): x

Expert command (? for help): ?

Expert menu commands include:

• a – Set attributes
• c – Change partition GUID
• d – Display sector alignment
• e – Relocate backup header
• g – Change disk GUID
• h – Recompute CHS values
• i – Show detailed information
• l – Set sector alignment
• m – Return to main menu
• n – Create new protective MBR
• o – Print protective MBR data
• p – Print partition table
• q – Quit without saving
• r – Recovery and transformation
• s – Resize partition table
• v – Verify disk
• w – Write table and exit
• z – Zap (destroy) GPT structures

Practical Examples and Use Cases

Setting Up a Boot Disk

Create a complete boot setup with EFI system partition:

sudo gdisk /dev/sda

# Create EFI System Partition
Command (? for help): n
Partition number: 1
First sector: (default)
Last sector: +512M
Hex code: EF00

# Create root partition
Command (? for help): n
Partition number: 2
First sector: (default)
Last sector: +20G
Hex code: 8300

# Create swap partition
Command (? for help): n
Partition number: 3
First sector: (default)
Last sector: +4G
Hex code: 8200

# Create home partition
Command (? for help): n
Partition number: 4
First sector: (default)
Last sector: (default - use remaining space)
Hex code: 8302

RAID Setup Preparation

Prepare partitions for software RAID:

# Create RAID partition
Command (? for help): n
Partition number: 1
First sector: (default)
Last sector: (default)
Hex code: FD00

# Set partition name
Command (? for help): c
Partition number: 1
Enter name: RAID Member

Troubleshooting Common Issues

Fixing Corrupted GPT Headers

When encountering corrupted GPT headers:

sudo gdisk /dev/sda

# Access recovery menu
Command (? for help): r

# List recovery options
Recovery command (? for help): ?

Alignment Issues

Check and fix partition alignment:

# In expert mode
Expert command (? for help): d

Partition alignment:
Partition 1: 2048 sectors (1024K)
Partition 2: 2048 sectors (1024K)

# Verify alignment is optimal for SSD performance

Best Practices and Tips

Performance Optimization

• SSD Alignment: Ensure partitions are aligned to 2048 sectors (1MB) for optimal SSD performance
• Partition Order: Place frequently accessed partitions (like root) in faster outer tracks
• Reserve Space: Leave some unpartitioned space for over-provisioning on SSDs

Safety Measures

• Always Backup: Create partition table backups before making changes
• Verify Changes: Use the verify command (v) before writing changes
• Test First: Practice on virtual machines or test disks
• Double-check Device: Ensure you’re modifying the correct device

Integration with Other Tools

Working with mkfs

After creating partitions, format them appropriately:

# Format EFI system partition
sudo mkfs.fat -F32 /dev/sda1

# Format root partition
sudo mkfs.ext4 /dev/sda2

# Setup swap
sudo mkswap /dev/sda3

LVM Integration

Create LVM physical volumes on gdisk partitions:

# Create LVM partition with gdisk (type 8E00)
sudo pvcreate /dev/sda3
sudo vgcreate vg01 /dev/sda3
sudo lvcreate -L 10G -n lv_root vg01

Comparison with Other Tools

Conclusion

The gdisk command is an essential tool for modern Linux system administrators working with GPT partition tables. Its comprehensive feature set, interactive interface, and robust error handling make it the preferred choice for managing large disks, UEFI systems, and complex partition layouts. Whether you’re setting up new systems, converting legacy MBR setups, or troubleshooting partition issues, gdisk provides the precision and reliability needed for professional disk management.

Remember to always backup important data and partition tables before making changes, and take advantage of gdisk’s verification features to ensure data integrity. With practice and understanding of GPT concepts, gdisk becomes an invaluable tool in your Linux administration toolkit.