+++
title = "Formatting MacOS Disk on Command Line"
date = 2021-08-01T00:00:00
lastmod = 2021-08-01T00:00:00
draft = false

# Authors. Comma separated list, e.g. `["Bob Smith", "David Jones"]`.
authors = ["Carl Pearson"]

tags = ["c3sr"]

summary = "What to do when Disk Utility won't"

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+++

For reasons beyond my comprehension, macOS's Disk Utility randomly won't format external drives.

For example, here's what disk utility shows when I first plug in the flash drive.

![](step1.png)

Here's the error when I try to format it as ExFAT.

![](step2.png)

Instead, use the `diskutil` command to first `list` the disks to find out which one is the offending disk `disk4` in this case) and then reformat it with something like `diskutil eraseDisk [format] [name] [disk]`.

![](step3.png)