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Formatting to FAT32 on FreeBSD

06 Feb 2025

Formatting drives on any operating system can be a handful of instructions specific to that operating environment. In today’s post we’ll walk through the process of formatting a USB drive to FAT32, explaining each command along the way.

Identifying the Device

Before making any changes, you need to determine which device corresponds to your USB drive. The best way to do this is:

dmesg | grep da

or, for a more detailed view:

geom disk list

On FreeBSD, USB mass storage devices are typically named /dev/daX (where X is a number). If you only have one USB drive plugged in, it is likely /dev/da0.

Device naming in FreeBSD is quite uniform:

  • USB Drives: /dev/daX
  • SATA/SAS/IDE Drives: /dev/adaX
  • NVMe Drives: /dev/nvmeX
  • RAID Volumes: /dev/mfidX, /dev/raidX

Partitioning the Drive

Now that we know the device name, we need to set up a partition table and create a FAT32 partition.

Destroying Existing Partitions

If the drive has existing partitions, remove them:

gpart destroy -F /dev/da0

This ensures a clean slate.

Creating a Partition Table

We create a Master Boot Record (MBR) partition table using:

gpart create -s mbr /dev/da0
  • -s mbr: Specifies an MBR (Master Boot Record) partition scheme.
  • Other options include gpt (GUID Partition Table), which is more modern but may not be supported by all systems.

Adding a FAT32 Partition

Now, we create a FAT32 partition:

gpart add -t fat32 /dev/da0
  • -t fat32: Specifies the FAT32 partition type.
  • Other valid types include freebsd-ufs (FreeBSD UFS), freebsd-swap (swap partition), freebsd-zfs (ZFS), and linux-data (Linux filesystem).

After running this command, the new partition should be created as /dev/da0s1.

Formatting the Partition as FAT32

To format the partition, we use newfs_msdos:

newfs_msdos -L DISKNAME -F 32 /dev/da0s1
  • -L DISKNAME: Assigns a label to the volume.
  • -F 32: Specifies FAT32.
  • /dev/da0s1: The newly created partition.

Why /dev/da0s1 instead of /dev/da0?
When using MBR, partitions are numbered starting from s1 (slice 1), meaning that the first partition on da0 becomes da0s1. Using /dev/da0 would format the entire disk, not just a partition.

Wrapping Up

At this point, your USB drive is formatted as FAT32 and ready to use. You can mount it manually if needed:

mount -t msdosfs /dev/da0s1 /mnt

To safely remove the drive:

umount /mnt

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