How to Format a USB Pendrive in Linux (Engineer’s Command-Line Guide)

Formatting USB storage devices—pendrives, external SSDs, backup sticks—directly from the Linux command line is often faster, more reliable, and far more precise than clicking through a GUI. Engineers dealing with mixed-OS environments or prepping boot media already know: graphical tools fail unpredictably. The CLI rarely misstates intentions.

Below, you’ll find exact steps (verified with Debian 12, util-linux 2.38, and dosfstools 4.2), edge considerations, and tips on establishing FS consistency across environments.

Device Detection: Pinpoint Your USB

A single error here wipes the wrong disk. Half the format failures I’ve seen trace back to unclear device identification.

Insert the pendrive, then:

lsblk -p -o NAME,SIZE,RM,MODEL,MOUNTPOINT

Sample output:

NAME        SIZE RM MODEL           MOUNTPOINT
/dev/sda   512G  0 Samsung_SSD_860 /, /home, /boot
/dev/sdb    16G  1 SanDisk_Cruzer  /media/deploy/USB16
├─/dev/sdb1 16G  1                  /media/deploy/USB16

The pendrive is /dev/sdb. Don’t trust df -h; partition names shift after reboots.

Caution: Matching the MODEL field sometimes surfaces when you have multiple disks of the same size.

Unmount All Mountpoints

Don’t skip this: formatting a mounted filesystem triggers errors like:

mkfs.vfat: /dev/sdb1 contains a mounted filesystem

Standard umount (for all present partitions):

sudo umount /dev/sdb1

For drives with multiple partitions, repeat for each /dev/sdbX.

(Optional, Nuclear) Zero the Partition Table

If legacy partitioning or “phantom” partitions persist, a surgical wipe is best:

sudo dd if=/dev/zero of=/dev/sdb bs=1M count=10 status=progress

Note: This will obliterate the first 10MB—enough for GPT/MBR/EFI traces. For secure disposal, increase count or use shred.

If your OS automounts after insertion, expect dmesg noise or auto-remounts immediately after. Disable automount or be quick.

Create a New Partition Table

MBR vs. GPT? FAT32 only supports MBR, while exFAT and ext4 handle GPT. For maximum compatibility (e.g., BIOS boot disks), stick with MBR.

Partitioning Example (fdisk, MBR):

sudo fdisk /dev/sdb

At the prompt:

• o — clear to DOS (MBR) table
• n, p, ENTER — new primary partition, default number and sectors (full drive)
• t, b — type W95 FAT32 for cross-compatibility.
• w — write changes

Tip: For bootable USBs, set the partition bootable with a before writing.

GPT Alternative: Use g for a GPT table. Required for >2TB sticks.

Create Filesystem

Here’s where intended usage dictates choice:

For exFAT, install tools:

sudo apt-get install exfatprogs   # Ubuntu ≥20.04

Old Ubuntu: exfat-utils.

Side note: Formatting with -n <label> embeds a volume label. Not all tools accept the same flags.

Verify Filesystem

Check that the device reports the intended FS:

lsblk -f /dev/sdb1

Sample:

NAME   FSTYPE LABEL      UUID                                 MOUNTPOINT
sdb1   vfat   USBDATA    3C1A-2B9D

Or, for blunt verification:

sudo file -s /dev/sdb1

Yields:

/dev/sdb1: DOS/MBR boot sector; FAT (32 bit);...

Label the Filesystem (Optional)

Volume labels are not cosmetic; they appear in mount dialogs and scripts.

• For FAT32:

  sudo dosfslabel /dev/sdb1 ENGINEERUSB
  

• exFAT:

  sudo exfatlabel /dev/sdb1 XFER_2024
  

• ext4:

  sudo e2label /dev/sdb1 linux_backup
  

Common Pitfalls and Pro Tips

• Auto-mount interference: Gnome and KDE often re-mount unmounted devices instantly. Unmount, format, then unplug/replug if in doubt.
• Hidden Windows partitions: If drive won't mount in Windows after using GPT, use MBR and set partition type.
• Performance tuning: For ext4 with SSD pendrives, consider -O ^has_journal for reduced FS wear.
• mkfs errors: If mkfs fails with "Permission denied", double-check the block device: OS often changes device name after replug.

Quick Reference Table

Notes from the Field

Formatting via CLI offers complete visibility into each stage and avoids the “unknown error” GUI problem. For field deployments or rescue workflows, scripting these steps ensures reproducibility at scale. Not perfect: some cheap USB devices occasionally report successful writes but silently discard data—always verify with md5sum or similar if data integrity matters.

For further automation (bulk formatting/testing), consider using parted --script, wipefs, or udev rules—however, manual fdisk remains more reliable for single-drive ops and safeguards against batch mistakes.

Further Topic?
If precise mounting, multi-partition USB layouts, or automated provisioning pipelines for boot media are required, these can be covered separately—each topic introduces its own subtle complexities.