cgdisk Command Linux: Complete Guide to Curses-Based GPT Partition Management

The cgdisk command is a powerful curses-based GPT (GUID Partition Table) partition editor for Linux systems. Unlike traditional command-line tools, cgdisk provides an interactive, menu-driven interface that makes GPT partition management more intuitive while maintaining the precision required for system administration tasks.

What is cgdisk Command?

cgdisk is part of the GPT fdisk (gdisk) package and serves as a curses-based frontend for GPT partition manipulation. It combines the power of command-line partitioning tools with a user-friendly text-based interface, making it ideal for both beginners and experienced system administrators who prefer visual feedback when managing disk partitions.

Key Features of cgdisk

• Interactive Interface: Menu-driven operations with keyboard navigation
• GPT Support: Native support for GUID Partition Tables
• Real-time Feedback: Visual representation of partition changes
• Safety Features: Built-in warnings and confirmation prompts
• UEFI Compatible: Perfect for modern UEFI systems

cgdisk Syntax and Basic Usage

The basic syntax for cgdisk is straightforward:

cgdisk [options] device

Common Options

Installing cgdisk

Before using cgdisk, ensure it’s installed on your system:

Ubuntu/Debian:

sudo apt update
sudo apt install gdisk

CentOS/RHEL/Fedora:

sudo yum install gdisk
# or for newer versions
sudo dnf install gdisk

Arch Linux:

sudo pacman -S gptfdisk

Getting Started with cgdisk

Let’s explore cgdisk with practical examples. First, let’s launch cgdisk on a disk:

sudo cgdisk /dev/sdb

Example Output:

                                 GPT Partitions Tool v1.0.9
                                   /dev/sdb (8.0 GiB)

   Part. #     Size        Partition Type            Partition Name
________________________________________________________________
              8.0 GiB     free space

[ Align  ] [ Backup ] [ Delete ] [ Help   ] [ Info   ] [ Load   ]
[ naMe   ] [ New     ] [ Print  ] [ Quit   ] [ reCover] [ Sort   ]
[ Verify ] [ Write   ]

                        Press the highlighted key for action

cgdisk Interface Navigation

The cgdisk interface consists of several key areas:

Main Display Elements

• Header: Shows tool version and disk information
• Partition Table: Lists all partitions with details
• Command Menu: Available actions at the bottom
• Status Bar: Instructions and feedback

Navigation Keys

Creating New Partitions

Let’s create a new partition using cgdisk’s interactive interface:

Step-by-Step Partition Creation

1. Launch cgdisk:

sudo cgdisk /dev/sdb

2. Select “New” option: Press ‘n’ or navigate to [New]
3. Specify partition details:

First sector (2048-16777182, default = 2048): [Enter for default]
Size in sectors or {KMGTPE} (default = 16775135): +2G
Current type is 'Linux filesystem'
Hex code or GUID (L to show codes, Enter = 8300): [Enter for Linux filesystem]
Current partition name is ''
Enter new partition name, or press Enter to use the current name: MyData

Result Display:

                                 GPT Partitions Tool v1.0.9
                                   /dev/sdb (8.0 GiB)

   Part. #     Size        Partition Type            Partition Name
________________________________________________________________
   1           2.0 GiB     Linux filesystem          MyData
              6.0 GiB     free space

Common Partition Types and Codes

cgdisk supports numerous partition types. Here are the most commonly used ones:

Advanced cgdisk Operations

Modifying Existing Partitions

Let’s modify an existing partition’s properties:

1. Select the partition: Use arrow keys to highlight the target partition
2. Access Info menu: Press ‘i’ to view detailed information

Partition GUID code: C12A7328-F81F-11D2-BA4B-00A0C93EC93B (EFI System)
Partition unique GUID: 12345678-1234-5678-9ABC-DEF012345678
First sector: 2048 (at 1024.0 KiB)
Last sector: 1050623 (at 513.0 MiB)
Partition size: 1048576 sectors (512.0 MiB)
Attribute flags: 0000000000000000
Partition name: 'EFI System Partition'

Changing Partition Names

To change a partition name:

1. Select the partition
2. Press ‘m’ for naMe option
3. Enter the new name

Enter new partition name, or press Enter to use the current name: Boot-Partition

Creating a Complete Partition Scheme

Let’s create a typical Linux installation partition scheme:

Example: Setting up EFI + Root + Home + Swap

# Launch cgdisk
sudo cgdisk /dev/sdb

# Create EFI System Partition (512MB)
New → First sector: [default] → Size: +512M → Type: ef00 → Name: EFI

# Create Root Partition (30GB)
New → First sector: [default] → Size: +30G → Type: 8300 → Name: Root

# Create Home Partition (remaining space - 4GB for swap)
New → First sector: [default] → Size: -4G → Type: 8300 → Name: Home

# Create Swap Partition (4GB)
New → First sector: [default] → Size: [default] → Type: 8200 → Name: Swap

Resulting Partition Table:

                                 GPT Partitions Tool v1.0.9
                                   /dev/sdb (64.0 GiB)

   Part. #     Size        Partition Type            Partition Name
________________________________________________________________
   1         512.0 MiB     EFI System                EFI
   2          30.0 GiB     Linux filesystem          Root
   3          29.5 GiB     Linux filesystem          Home
   4           4.0 GiB     Linux swap                Swap

cgdisk Safety Features

Verification and Backup

cgdisk includes several safety mechanisms:

Verify Command (‘v’)

Checks partition table integrity:

No problems found. 65535 free sectors (32.0 MiB) available in 1
segments, the largest of which is 65535 (32.0 MiB) in size.

Backup Command (‘b’)

Creates a backup of the current partition table:

Enter backup filename to save: backup_partition_table.gpt
The backup GPT data have been saved to backup_partition_table.gpt

Error Handling and Troubleshooting

Common Issues and Solutions

Issue: “Device is busy” Error

Error: Device /dev/sdb is busy

Solution:

# Unmount all partitions on the device
sudo umount /dev/sdb*

# Check for active processes
sudo lsof | grep /dev/sdb

# Kill processes if necessary
sudo fuser -k /dev/sdb

Issue: Partition Alignment Warnings

Warning: Partition 1 does not end on a sector boundary.

Solution: Use the Align command (‘a’) to fix alignment issues automatically.

Recovery Operations

If you need to recover a damaged partition table:

1. Use the reCover command (‘r’):

                         recovery/transformation menu

b   use backup GPT header (rebuilding main)
c   load backup partition table from disk (rebuilding main)
d   use main GPT header (rebuilding backup)
e   load main partition table from disk (rebuilding backup)
f   load MBR and build fresh GPT from it
g   convert GPT into MBR and exit
h   make hybrid MBR
i   show detailed information on a partition
l   load partition data from a backup file
m   return to main menu
o   print protective MBR data
p   print the partition table
q   quit without saving changes
t   transform BSD disklabel partition
v   verify disk
w   write table to disk and exit
x   extra functionality (experts only)
?   print this menu

Best Practices for cgdisk Usage

Pre-operation Checklist

• Always backup important data before partitioning
• Unmount target partitions before modification
• Verify disk identification to avoid wrong device operations
• Use verification commands before writing changes

Recommended Workflow

1. Plan your partition layout on paper first
2. Launch cgdisk and examine the current state
3. Create backup of existing partition table
4. Make changes incrementally and verify each step
5. Use Print command (‘p’) to review before writing
6. Write changes only when satisfied with the layout

Comparing cgdisk with Other Tools

Advanced Features and Expert Mode

Expert Functionality

Access expert mode through the recovery menu (‘r’ → ‘x’):

                            Expert command menu

a   set attributes
c   change partition GUID
d   display the sector alignment value
e   relocate backup data structures to the end of the disk
g   change disk GUID
h   recompute CHS values in protective/hybrid MBR
i   show detailed information on a partition
l   set the sector alignment value
m   return to main menu
n   create a new protective MBR
o   print protective MBR data
p   print the partition table
q   quit without saving changes
r   recovery and transformation options
s   resize partition table
t   transpose two partition table entries
u   Replicate partition table on new device
v   verify disk
w   write table to disk and exit
z   zap (destroy) GPT data structures and exit
?   print this menu

Setting Partition Attributes

Modify partition attributes for special behaviors:

# In expert mode, select 'a' for attributes
Current attributes are: 0000000000000000
Set fields are:
  0 (system partition)
  1 (hide from EFI)
  2 (legacy BIOS bootable)
 60 (read-only)
 62 (hidden)
 63 (do not automount)

Toggle which attribute field (0-63, 64 or  to exit): 0
Have enabled the 'system partition' attribute.
Attribute value is 0000000000000001.

Practical Use Cases

Use Case 1: Setting up UEFI Boot Drive

sudo cgdisk /dev/nvme0n1

# Create partitions:
# 1. EFI System Partition (512MB, ef00)
# 2. Boot partition (1GB, 8300)
# 3. Root partition (remaining, 8300)

# Set EFI partition attributes in expert mode
# Enable system partition and EFI system partition attributes

Use Case 2: Preparing Drive for Linux RAID

sudo cgdisk /dev/sdc

# Create RAID partitions with type fd00
# Name them consistently (raid1, raid2, etc.)
# Ensure all partitions have identical sizes

Integration with File Systems

After creating partitions with cgdisk, format them appropriately:

# Format EFI partition
sudo mkfs.fat -F32 /dev/sdb1

# Format ext4 partitions
sudo mkfs.ext4 /dev/sdb2
sudo mkfs.ext4 /dev/sdb3

# Setup swap
sudo mkswap /dev/sdb4

Conclusion

The cgdisk command provides a powerful yet user-friendly interface for GPT partition management in Linux. Its curses-based interface bridges the gap between command-line efficiency and graphical ease-of-use, making it an excellent choice for system administrators and advanced users who need precise control over disk partitioning.

By mastering cgdisk’s interactive interface, safety features, and advanced capabilities, you can confidently manage modern GPT-based storage systems while minimizing the risk of data loss through its built-in verification and backup mechanisms.

Whether you’re setting up new systems, reorganizing existing storage, or preparing drives for specific use cases like RAID or LVM, cgdisk offers the flexibility and reliability needed for professional disk management tasks.