A disk image is a container you can place your files and folders in. You can store whatever files you want in a disk image, and you can encrypt the disk image to prevent unauthorized access to your files or even burn the disk image to a CD/DVD.
In Mac OS X when you double-click a disk image, instead of launching like an app, it gets mounted as a volume on your machine and can be accessed as if you were accessing an external hard drive. That feature distinguishes it from the other file types.
If you wish to create a disk image for your file storage, you may want to create a blank one. Creating a blank disk image is an effortless process on a Mac, and the following guide should help you create one.
Creating a Blank Disk Image
In order to create a disk image, you only need access to the “Disk Utility” on your Mac.
1. Click on Launchpad in your dock. Search for and click “Disk Utility.”
2. When the utility launches, click on the “File” menu followed by “New Image” and then select “Blank Image…”
3. A dialog box should appear asking you to input the details for your disk image. Input the following information:
Save As – Enter a name for the disk image. It can be any name of your choice.
Tags – Assign tags to the disk image, if you wish. It is completely optional though.
Where – Specify a location where you wish to save the disk image.
Name – Enter a name that will appear in the Finder when the disk image is mounted. Again, it can be a name of your choice.
Size – Specify the size of the disk image. Make sure you enter a value followed by the unit (200 is incorrect; 200 MB is correct).
Format – Enter the disk image file format. If you are going to be using the disk image on a Windows computer, select either MS-DOS (FAT) or ExFAT. The other two formats will not work with Windows. For a Mac, just select any format, and it will work.
Encryption – Specify an encryption type here if you would like your disk content to be encrypted. Select “none” if you do not want your files to be encrypted.
Partitions – Select a partition type here. If you are not sure, select the “No partition map” option.
Image Format – This allows you to select the format of your disk image. For a blank disk image that will be used to store files, the “read/write disk image” should be a good one.
Once you have entered all the details, click on the “Save” button.
4. Your Mac should take a few seconds to create the image. Once the image has been created, you will see the following message and need to click on “Done” to move forward.
5. Your disk image has been created and is mounted on your Mac for you to copy files to it. You can just drag and drop your files onto the disk image, and they will be added.
Once you are done adding files, you can eject the image by clicking on the eject icon next to the image name in the Finder. When needed, you can re-open the image by double-clicking on it.
If you would like to create a disk image on your Mac to store your files, the above guide helps you create a blank one that can then be read and written to for you to add and delete files.