Disk Utility is an excellent app integrated into Mac OS X for managing our drives. We can use it to format a drive to a different file system, and resize, create, or delete partitions. Let's see how to make the most of Disk Utility and take control of our drives.
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We have prepared this guide on OS X 10.11.1 El Capitan. It should work on recent earlier and later versions of Mac OS X. It will also work for the Mac OS X Virtual Machine on Windows or Linux.
Table of Contents
How to access Disk Utility on Mac OS X
The fastest way to access the Mac OS X partitioning app is to press Command ⌘ + Space to open the Spotlight Search and begin typing "Disk Utility" - the autocomplete will kick in after "Disk", so we won't have to enter the whole thing.
Also, if we connect an unformatted drive to our Mac, the system will automatically prompt to initialize the disk. Clicking the "Initialize..." button will open Disk Utility.
How to resize and create partitions on Mac OS X with Disk Utility
By default, Disk Utility will open with the Mac OS X system partition selected, showing a breakdown of its usage.
As you can notice, most of the app's options are grayed out. To resize the partition and create a new partition - to use with Time Machine or to install an alternative operating system - we need to select the parent drive.
Run First Aid first
Partitioning is relatively safe, but it always carries the risk that something could go wrong, and we could lose our data.
To reduce the risk, it's a good idea to check the disk for errors. On Mac OS X, we can do that by running First Aid the drive or partition.
On a normal drive, it will take just a couple of seconds, and offer some peace of mind.
Resize a partition and create new partitions
With the drive selected, we click the Partition button to change the disk's partitions.
Clicking on the "+" will halve the capacity of the currently selected partition and create a new partition of equal size.
Using the slider on the partition pie, we can shrink or enlarge the new partition.
There are a few different file systems to format the new partition. The default is OS X Extended (Journaled).
A journaling file system will keep track of file and directory changes that aren't yet committed to the primary file system, by recording them in a data structure called "journal". This way, in the case of a system crash or power failure, the changes won't be lost.
The Case-sensitive option will differentiate between files or directories with the same name written with different case letters, such as "file" and "File". This is the default setting for the most popular Linux file systems.
The encrypted options will encrypt and password-protect the contents of the partition. Make sure not to forget the password, because it will be next to impossible to recover the data.
MS-DOS (FAT) is the most compatible option. Any PC, operating system, and other devices (Smart TV, car stereo, etc.) can access FAT partitions. However, FAT has a file size limit of 4GB - 1 byte per file; it can't handle larger files.
ExFAT is the latest version of FAT, which has a theoretical file size limit of 16 Exbibytes = 260 bytes. Windows 7, 8.1, and 10 will recognize ExFAT but it won't work on Windows XP without Windows update KB955704, or on Windows Vista without SP2.
Disk Utility doesn't have an NTFS option. We will need an alternative app to format a partition as NTFS.
Apply the changes
Until we click on "Apply", nothing will change on the hard drive. We can cancel anytime, and it will be like we never run Disk Utility.
Disk Utility applies most of the changes in real time, without the need to reboot or boot on an external environment.
After creating a new partition and if we haven't set up Time Machine yet, the system will ask us if we want to use the new partition for our Mac OS X backups. Feel free to decline.
Did you have any problems with Disk Utility?
If anything on the guide didn't work as described, and you weren't able to use Disk Utility to manage your Mac's disks and partitions, leave us a comment.
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