How to Erase a Disk from Command Line in Mac OS X

Aug 30, 2016 - 12 Comments

Erase disk from command line of Mac OS

Some Mac users may require the ability to erase a disk or erase a hard drive from the command line on Mac OS, a task which is typically performed through the Disk Utility application from the GUI. The command line approach to disk erasure in macOS is a bit different and it requires precise syntax to insure that you are erasing the proper disk, making this method of erasing any disk only appropriate for advanced Mac users.

This guide will walk through how to erase and format an entire target disk using exclusively the command line on any Mac using macOS or Mac OS X. You can choose any common file system format the disk to after it has been erased, including ExFAT, FAT32, HFS+, or JHFS+.

Notice that this is aiming to erase the entire disk from the command line here, this is not just erasing a volume or partition on the target disk. The entire target disk is erased, all data on the target disk is destroyed using this approach, with no volumes or partitions or any data remaining. Do not misunderstand that, otherwise you will inevitably permanently lose data when it is erased and destroyed. Remember the command line is unforgiving, if you are not comfortable at the command line it would be much more appropriate to erase and format a disk using Disk Utility in the standard interface of Mac OS X.

Erasing a Disk from the Command Line of Mac OS

To erase a disk from the command line on the Mac, we’ll use the familiar “diskutil” command with the eraseDisk verb and other appropriate flags to specify options for how we want to erase the disk, and to identify which disk is to be erased.

The basic syntax for erasing a disk from the command line in macOS is as follows:


For example, let’s say you have used “diskutil list” to show all of mounted drives on a Mac from the command line, and you have determined the appropriate drive to erase is identified as /dev/disk6s2, you want the disk name to be “Emptied” and you want the new disk file system format type to be Mac OS Extended Journaled (JHFS+), the syntax would be the following:

diskutil eraseDisk JHFS+ Emptied /dev/disk6s2

It is absolutely critical that you use proper syntax when identifying the disk to erase. Improper identification may lead to erasing the wrong disk, permanently destroying any data on it. Do not screw this up. If you are unsure, you can find the disk ID node with “diskutil info “DISK NAME” |grep Device”.

For some quick reference, here are a few examples of various disk erasure methods for different file system format types. As always, be sure you change the disk node as appropriate for your disk.

Formatting a Disk to Mac OS Extended Journaled (JHFS+) from Terminal in Mac OS X

diskutil eraseDisk JHFS+ DiskName /dev/DiskNodeID

Formatting a Disk to Mac OS Extended (HFS+) from Terminal in Mac OS X

diskutil eraseDisk HFS+ DiskName /dev/DiskNodeID

Formatting a Disk to MS-DOS fat32 from the Command Line in Mac OS X

diskutil eraseDisk FAT32 DiskNameGoesHere /dev/DiskNodeIDHere

Formatting a Disk to ExFAT from the Command Line in Mac OS X

diskutil eraseDisk ExFAT DiskName /dev/DiskNodeID

Again, any of these commands erase the entire target disk and obliterates any data on it.

Users who would like additional details or information about the other options available including MBR and GPT settings can query the man page with “man diskutil” and searching for “eraseDisk”, or execute the command with no specifics like so:

diskutil eraseDisk
Usage: diskutil eraseDisk format name [APM[Format]|MBR[Format]|GPT[Format]]
Completely erase an existing whole disk. All volumes on this disk will be
destroyed. Ownership of the affected disk is required.
Format is the specific file system name you want to erase it as (HFS+, etc.).
Name is the (new) volume name (subject to file system naming restrictions),
or can be specified as %noformat% to skip initialization (newfs).
You cannot erase the boot disk.
Example: diskutil eraseDisk JHFS+ UntitledUFS disk3

Finally, it’s worth mentioning that if you want to erase the currently booted disk from the command line from this method, you’d want to do so from a boot disk or from recovery mode. Single User Mode alone is not sufficient to erase the actively booted operating system.

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Posted by: Paul Horowitz in Command Line, Mac OS X, Tips & Tricks


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  1. Bev in TX says:

    Thanks for the interesting article. I do have one question because I don’t understand the difference between:

    Mac OS Extended Journaled:
    diskutil eraseDisk JHFS+ DiskName /dev/DiskNodeID


    MS-DOS fat32:
    diskutil eraseDisk JHFS+ DiskNameGoesHere /dev/DiskNodeIDHere

    Should the MS-DOS one use FAT32 instead of JHFS+? Or am I misunderstanding something?

  2. Bob says:

    Why publish such dangerous commands which might create disasters for the adventurous amateur.

    • tgrudzin says:

      The spreading of knowledge should never be discourage. If “adventurous amateur” create disasters, then so be it. They will learn something from it. And no great disaster will occur. They might lose ‘everything important to them’. That isn’t a disaster. My story is I hand off USB and other older hard drives. I’m a photogrpaher. I’d like to be sure that previous data is gone. One way I was taught was to hard format a drive in Windows, then do similar in Mac, then again format in Windows, then add the data. For jpgs, this should elimant many software recovery options.

  3. Sean says:

    Thanks for that info.
    Is there any speed advantage to this method over the GUI?

    • Paul says:

      No it’s the same erase process, it’s just handled through the command line rather than the Disk Utility GUI app.

  4. Alex says:


    If you want to erase and empty the disk (no new file system):

    diskutil erasedisk free %noformat% MBR diskname

  5. Mark Ross says:

    I have a question that is related. . . sort of.

    Why is Apple holding back from implementing a modern disk file system on their computers? The specs for one of these was offered to them (and basically everyone else) free of charge, quite a few years ago by Sun Microsystems.

    Remember ZFS?

    Would it have been simple to implement? Oh, probably not.

    Were any of the other file systems in use today simple to implement? I’m guessing not.

    Apple charges a higher than normal price for what I will admit is a higher than normal quality machine.

    I just think it’s time the quality of the filing system on the hard drive be brought up to Apple standards. The status quo doesn’t cover it and Apple has never been known to settle for ‘status quo’, anyway.

    So, please, put a few of your brilliant engineers on this, would ya? Failure should not be an option.

    Or, maybe you’re just waiting for hard drives to go away completely? Now, THAT’S an interesting thought.

    Mark Ross
    Apple Customer

    • Sam Cooke says:

      Apple is working on APFS, or Apple File System, but it won’t be used for at least another year. Maybe they will release new Macs in that time that could use it.

  6. Ian says:

    Very recently, I came across a situation where Disk Utility could not erase the HDD. Under the strictest supervision from Apple, I was able to do this from the command line. As it was a Fusion Drive, I was then instructed on how to merge or fuse the two disks – SSD and spinning platter. It all worked perfectly in the end BUT this is NOT for the amateur or faint hearted.

  7. Ryszart says:


    I’m just wondering, how do you make your terminal look like that? I don’t see any option in Terminal preferences or in global preferences, apart of Dark mode, which doesnt work for window borders…

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