How to Recover Data After Format. We all make mistakes, and you wouldn't be the first person in the world to accidentally format a USB flash drive. Disk Drill, a premium data recovery solution for Mac OS X with support for all popular file formats and common storage devices, is here to help you recover deleted files from USB flash drive.
Nowadays, when you buy a USB drive, you can use it right out of the box with your Mac. However, unless it's been designed for use with a Mac, it won't be formatted using macOS' preferred file system (either Mac OS Extended or APFS, depending on which version of macOS you're running).
That's because most of the computers in the world run Windows, and Windows uses a different file system, usually one known as Fat32. Drives formatted as Fat32 can be read from and written to by macOS, but it's not optimal and you're more likely to run into problems than if you use macOS' native format. So, if you've bought a USB drive that's formatted as Fat32, or any other format other than Mac OS Extended (also known as HFS+) or APFS, here's how to format a USB drive on Mac. It's exactly the same procedure if you need to reformat a flash drive on a Mac.
How to format a USB drive on a Mac
1. Plug the drive into a USB socket (if you have a recent MacBook or MacBook Pro that only has USB-C connectors, you'll need a USB-C to USB-A adaptor).
2. Open a new Finder window and click on the drive. Make sure it has no files on it that you need. The process of reformatting it will wipe all the data from it.
3. Once you've copied any files you need from the USB drive to your Mac, go to Applications>Utilities and double-click on Disk Utility.
4. Click on the USB drive in the sidebar and then choose Erase from the toolbar at the top of the window.
5. In the window that drops down type a name for the formatted drive in the box next to Name.
6. Choose a format from the dropdown menu.
7. If you have previously stored sensitive data on the drive, click the Security tab.
8. Choose a security level using the slider. The further to the right you move the slider, the more ‘passes' the erase tool will make and the more securely files will be deleted. However, it also increases the time it takes to format the drive quite considerably.
9. Click Ok then click Erase.
Tip: You don't need to erase a whole drive to delete files securely. If you have confidential files or sensitive data you need to remove from your Mac completely, you should use CleanMyMac's File Shredder. It's specifically designed to securely delete sensitive data and will render it unrecoverable. You can download CleanMyMac X for free here.
Which format to choose?
If your Mac is running macOS High Sierra or later, you have two options for file formats: APFS and Mac OS Extended. Which should you choose? The key point is that disks formatted as APFS won't be recognized by Macs running versions of macOS older than High Sierra. So if you think you might need to plug the USB drive into a Mac running an older version of macOS, format it as Mac OS Extended.
APFS is optimized for SSD (solid state drive) such as flash drives, so if you reformat a flash drive on a Mac, you should definitely choose APFS (unless you plan to use it with a pre-High Sierra Mac, of course). Even on hard drives, however, APFS is faster and more reliable than Mac OS Extended.
Finally, if you plan to use the USB drive as a destination for Time Machine backups, choose Mac OS Extended. Time Machine can't currently back up to an APFS disk and if you select one for use with Time Machine, it will offer to reformat it as Mac OS Extended. You can, however, backup an APFS formatted disk to a Mac OS Extended Time Machine drive.
How to format a USB drive to FAT32 on a Mac
The main reason for formatting a USB drive as Fat32 on a Mac is that you want to be able to use the drive on a Windows PC, as well as a Mac — perhaps to transfer files between the two machines. You may also be preparing the drive for use as, say, a storage device for a media player or to record TV programmes on a TV with a USB port.
The fact that Fat32 can be read from and written to on both Mac and Windows makes it very versatile. However, there is a significant limitation — individual files have a maximum size of 4GB. So, if you're using the USB drive to store large video files, you may run into trouble. There is a solution, however, exFAT. Unlike FAT32, exFAT doesn't have a maximum file limit. Better still, it can be read from and written to on any Mac running Mac OS X Snow Leopard or later and on Windows.
To format a USB drive in FAT32 or exFAT:
1. Plug the USB drive into your Mac.
2. Go to Applications>Utilities and launch Disk Utility.
3. Click on the USB drive in the sidebar in Disk Utility.
4. Click Erase in the Disk Utility toolbar.
5. Type in a name for the formatted disk.
Dmg File For Mac
6. Click on the Format menu and choose either MS-DOS (FAT32) or ExFAT.
7. Click Erase.
Your USB drive will now be erased and re-formatted as either FAT32 or ExFAT, depending on the format you chose in step 6.
How to manage your drives easily
If you look for a quick and easy way to manage your drives, try using CleanMyDrive 2. With its help, you can drag-and-drop files directly to any drive, clean hidden junk from external drives, and check disk stats. It works for all drives, including USB drives, SSD, SD cards, external hard drives. All the drives will be at hand in the menu bar, so you can get to see types of drives you have and manage them easily. CleanMyDrive is absolutely free to use, so download it on the Mac App Store and enjoy!
It's very easy to format a USB drive on a Mac using Disk Utility. There are a couple of things you should keep in mind, however. The first is that when you format and disk, you will erase all the data currently on it. So if you need that data, make sure you copy it onto another disk before you start. Secondly, there are several formats to choose from, each with advantages and disadvantage. Use the guide above to help you decide which is right for you.
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This guide covers the verbatim copying of a DMG image to a USB thumb drive using only Linux (no need to find a Mac). If the DMG was intended to be bootable then the resulting USB will be bootable.
Format Flash Drive Mac
Convert to ISO
Linux doesn't much care for DMG files. Sure, it'll play nice with them. But we don't just want to play nice. We want to copy a DMG image to a USB drive and keep it as verbatim as computationally possible. In order to do this, we're first going to convert the image to a format that's a little more universal: ISO.
We're going to use dmg2img to convert the DMG to an ISO image. If you already have dmg2img, great. If not, install it using your distribution's native package management system.
On Ubuntu, you'd do it like this:
Once you have dmg2img installed, begin converting the DMG file:
After a few minutes, you should have a second file called image.img. This file can be used like an ISO. All we have to do is change the extension. Use mv to do this:
Make sure you specified 'image.img' and not 'image.dmg'! Working with three different file extensions can get kind of confusing.
Ok, so we should now have a file called 'image.iso' which is just 'image.img' with a different extension.
Now we want to write 'image.iso' to our USB drive. I used 'lsblk' to figure out how the system was identifying my drive. The lsblk command lists all disks connected to the system. It's usually pretty easy to figure out which disk is which based on their size. Just be sure you're sure. This process is going to overwrite the target disk with the contents of our DMG image file. Any preexisting files on the target disk will be lost. As usual, make sure you have a proper backup.
Make sure the target drive isn't mounted. Unmount the drive with your distribution's GUI.
Or you could just unmount it from the terminal:
Most systems seem to mount external drives in /media. Sometimes the drive might be mounted in /mnt or elsewhere.
Write the ISO image to the USB drive like this:
Replace 'X' with the appropriate letter. For example '/dev/sdb'. Be sure to use the drive directly and not a partition within the drive. For example, don't use '/dev/sdb1'.
This will probably take a little while to complete. I'm using a Kingston DataTraveler DTSE9 and it took about 24 minutes 30 seconds to write 4.9GB.
Your new USB stick should now be bootable, assuming that was the intended purpose of the DMG.
