[solved] Mac OS X Won’t Erase USB

The usually painless process of creating a bootable linux usb was rather sucking today.

First, I’d get the “disk you inserted was not readable by this computer” error (below) but I wasn’t worried.


Then, when trying to erase it using Disk Utility, I’d get the “Erasing process has failed”.


Once, I think, it actually started to erase one of the USBs I tried before failing.

It was only after a couple tries that I clicked “Show Details” but that didn’t help Google help me find any answers. Not the answers I needed anyway.

I saw more than one post online about Sierra (I have High Sierra) failing to erase USB flash drives. The solution was using Disk Utilities > First Aid but that didn’t work for me.

As it turns out, the problem was the USB sticks in question were formatted as FAT-32 which, apparently, Mac can format to but not read from. So I did this (step-by-step instructions below screenshot):


In the terminal, type:

diskutil list

Carefully and accurately determine which disk is actually the one you actually want to actually erase — the 8GB size was the clue I wanted /dev/disk3. Using that information to erase the USB — not my hard drive — I typed:

diskutil unmountDisk force /dev/disk3

I’m not sure how much that step mattered for me as I don’t think my USBs were even mounting.

Lastly, type:

diskutil erasedisk MS-DOS UNNAMED /dev/disk3

Your formatting type may differ as might your disk identifier.

I went back to Disk Utility and, right away, it looked different.

BEFORE fixing it in the terminal. Note the 2.5 MB capacity with Zero KB available.
AFTER fixing it in the terminal. Note the 7.81 GB capacity with 7.79 GB available.

Finally, I went through my usual process to Create a bootable USB stick on macOS.

First, because I’m a stickler for following directions (follow the link for simple and easy instructions), I erased it in Disk Utility which, this time, gave me a happy, green checkmark.


I then used Etcher to, most triumphantly, create my bootable USB.


This is all an example of why MacOS rules and Windows drools. In the rare occasions something goes wrong, you can fix it easily. For the time being. Apple is, slowly but surely, f***ing that up on both counts and that is an example of why I increasingly use Linux instead.


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