Creating Linux Partitions with parted

GPT (GUID Partition Table) is required for disks larger than 2TB. The older MBR format maxes out at 2.2TB due to 32-bit sector addressing. Tools like fdisk will refuse to work properly with large drives and recommend switching to GPT. While parted has a steeper learning curve than some alternatives, it’s the standard for GPT manipulation on Linux.

Why GPT Matters

Any disk over 2TB needs GPT. This includes modern SSDs, large RAID arrays, and cloud storage volumes. If you run fdisk on a 6TB disk, it will either warn you or silently limit usable space to 2TB—a frustrating gotcha in production.

Basic Workflow: Creating a Single Partition

Here’s how to partition a new 6TB disk at /dev/sdc:

sudo parted /dev/sdc

This launches the interactive parted shell. First, create a GPT label:

(parted) mklabel gpt

You’ll see a warning that all data will be destroyed. Confirm with Yes if the disk is empty or you’ve backed up everything.

Now create a partition:

(parted) mkpart primary ext4 2048s 100%

The 2048s starting point aligns with 4K sector boundaries on modern SSDs, improving performance. The 100% uses all remaining space.

(parted) quit

Verify the partition was created:

parted /dev/sdc print

Output:

Model: Samsung SSD 870 (scsi)
Disk /dev/sdc: 6001GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt

Number  Start   End     Size    File system  Name     Flags
 1      1049kB  6001GB  6001GB               primary

Using Partition Labels

Named partitions are more reliable than device paths, especially when adding or removing disks:

(parted) mkpart storage ext4 2048s 100%
(parted) name 1 storage
(parted) quit

The partition is now accessible at /dev/disk/by-partlabel/storage. Use this in /etc/fstab:

/dev/disk/by-partlabel/storage  /mnt/storage  ext4  defaults  0 2

Non-Interactive Partitioning

For automation scripts, run parted commands directly without entering the shell:

sudo parted -a opt /dev/sdc mklabel gpt
sudo parted -a opt /dev/sdc mkpart storage ext4 0% 100%

The -a opt flag enables partition alignment optimization. This is ideal for CI/CD pipelines or provisioning tools like Terraform or Ansible.

Creating Multiple Partitions

To split a disk into boot, root, and data partitions:

(parted) mkpart boot ext4 2048s 1GB
(parted) mkpart root ext4 1GB 50%
(parted) mkpart data ext4 50% 100%
(parted) quit

Each partition gets a sequential number (/dev/sdc1, /dev/sdc2, /dev/sdc3).

Verifying Alignment

Before finalizing, check that partitions are properly aligned:

parted /dev/sdc align-check opt 1

Output should be:

1 aligned

Misaligned partitions reduce I/O performance on SSDs and RAID arrays.

Alternative Tools

gdisk provides a menu-driven interface similar to cfdisk:

sudo gdisk /dev/sdc

Install it with apt install gdisk (Debian/Ubuntu) or dnf install gdisk (RHEL/Fedora). It’s easier to learn if you’re uncomfortable with parted syntax, though parted is more widely available.

Formatting and Mounting

After partitioning, create a filesystem:

sudo mkfs.ext4 /dev/sdc1

For newer systems using Btrfs or XFS:

sudo mkfs.btrfs /dev/sdc1
# or
sudo mkfs.xfs /dev/sdc1

Mount and persist the mount:

sudo mkdir -p /mnt/storage
sudo mount /dev/sdc1 /mnt/storage

Then add to /etc/fstab for automatic mounting at boot. Use the partition label:

/dev/disk/by-partlabel/storage  /mnt/storage  ext4  defaults  0 2

Common Gotchas

Device busy errors: If parted says the disk is in use, ensure nothing is mounted and no processes hold open file handles:

sudo fuser -k /dev/sdc

Partition table not recognized after creation: If the kernel doesn’t see the new partitions, reload the partition table:

sudo partprobe /dev/sdc
# or
sudo blockdev --rereadpt /dev/sdc

Losing data during resizing: Always back up before modifying partitions. parted can resize partitions, but it’s risky:

sudo parted /dev/sdc resizepart 1 5TB

This should only be used when absolutely necessary and with verified backups.