Expert users may be frustrated and resort to learning the ins and outs of diskutil, the command-line utility available via Terminal that’s always had more switches and controls than the graphical Disk Utility.
But for many users who need to make quick and rare trips to this software, it could be an improvement: less frightening, easy to use, and harder to make mistakes.
One bit of terminology calibration before we proceed for those who don’t typically deal with disk settings. It’s typical to call a physical drive—whether a USB thumb drive, an SSD, or a hard drive—a drive. You format a drive to make its raw storage compatible with one or more operating systems. A physical drive has logical divisions, called partitions, that allow different formatting parameters on the same physical drive. Each mountable partition can appear as a separate disk icon in the Finder; these are often called volumes and, via Terminal, can be found in /Volumes directory.
Before digging into how to use the new setup, it’s important to note a key omission: Verify Permissions and Repair Permissions are gone. The sworn-by advice for years by experienced OS X users and Apple alike was to run Disk Utility and click Repair Permissions as the first step in troubleshooting something gone wrong: a printer driver failing, an app’s strange behavior, a weird interface glitch Repair permissions!
In OS X (and in all Unix and related OSes), a file or directory’s permissions associate which kind of user can perform what kind of action: read, write, execute (run, like a program), and other attributes. It made sense that repairing permissions on files for which OS X knew precisely what settings should be in place could fix random faults. A printer driver with the wrong switches flipped might not be available to the system; or the driver might be unable to access the printer settings file or temporary print queue directories. Even so, from all reports, permissions repairs had little real effect for years—it just made us feel better.
But in El Capitan, any system file for which Repair Permissions would have restored these settings can no longer be modified during normal operating. System Integrity Protection (SIP), also known as rootless mode, prevents modification to these files.
During El Capitan’s beta testing, one round of release notes from Apple explained the permissions removal from Disk Utility by noting that during software updates, any permission issues would be resolved by an installer, but that otherwise, there was no need. (If you disable SIP to use certain third-party software or unsigned kernel extensions, you’re on you own now.)
This new version of Disk Utility shows a prettier display when launched. As in the older versions, the boot partition is selected—the partition on a drive that holds the currently running OS X system. The list is divvied up into Internal, External, and Disk Images. However, instead of selecting the First Aid tab, Disk Utility now shows a variety of basic information about the partition.
This view may seem familiar if you’ve taken a trip recently to ? > About This Mac and clicked Storage. For volumes “blessed” as capable of being used as a startup drive, you’ll see a color-coded division—similar to that in iTunes for iOS devices—of how much storage is used and for what. For other regular volumes, just a yellow Other bar shows occupied space. Disk Utility only shows the division for the current booted volume, however.
The area beneath the drive icon and its summary offers a bit of technical detail, but not an overwhelming amount: the Unix mount point, like / with a boot drive; its type and connection; capacity, available, and used; and the logical name used by OS X (like disk3s2), which can be helpful if you need to plug it into diskutil or get remote help for your problem.
Where did all the other tools go They’re still there, but as buttons instead of tabs. Across the tab, you see First Aid (disk repair), Partition, Erase, Mount, and Info. Mount toggles to Unmount for volumes that are available in the Finder. (You can also click the eject button now next to any mounted volume in the list.)
Select a drive or a partition and click First Aid, and a seemingly much-changed repair operation proceeds. Unlike in its predecessor, Disk Utility can no longer verify a disk, making sure it’s OK without unmounting it or performing other operations. First Aid must be able to unmount a drive, or you’ll get an error. Click Show Details and you’ll see a bit more of what’s happening under the hood, as with the earlier release.
You can erase either a partition or an entire drive. Drives have both a format and a scheme: the scheme controls how the drive is prepared to be used to boot with different operating systems. Intel-based Macs need a GUID Partition Map; PowerPC ones, Apple Partition Map; and Windows (and DOS!), Master Boot Record. OS X can mount all three kinds, but only boot from the GUID flavor.
The several types under Format, whether for a drive or a partition, control filesystem-related issues. Here, you’ll almost always pick OS X Extended (Journaled) for best results. (To make a USB thumb drive or other disk to use with Windows, you may have to pick Master Boot Record as the scheme and ExFAT for cross-platform compatibility.)
The GUID Partition Map lets you resize partitions after they’ve been created and make new partitions, a boon compared to the olden days, when you had to back up an entire disk, reformat it, repartition it, and restore to change those formats. In the new Disk Utility, you drag a handle around a circle and click the + button to add new partitions.
Is a circle of pie slices a better representation of disk storage than the stacked rectangles used in earlier releases Hard to say: both refer to a linear range of locations on a physical disk and yet appear in two dimensions!
Finally, with any item select at left, click Info and receive a cavalcade of lower-level system detail useful for troubleshooting without diving into Terminal.
As in previous versions, Disk Utility has several options for disk images, such as verifying, creating a checksum (which allows verification by others), resizing, and converting the type. You can create a disk image from any folder (File > New Image > Image from Folder) or any selected mounted volume (File > New Image > Image from [Name]). The Blank Image option remains unchanged from recent releases.
Copying has become more obscure than the previous version. Technically, a copy happens via restore. You select a mounted volume or a disk image you’ve added to Disk Utility and then select Edit > Restore. You then choose the source that you want to overwrite the selected item, whether another mounted volume or a disk image. Restore is often used with backups, hence the name, but it’s just a backwards-described copy.
You used to be able to drag disk images from the Finder into Disk Utilities drive and volume view, but that no longer works. You have to choose File > Open Disk Image and select the file to bring it under management.
Disk Utility’s latest incarnation should be less daunting to the less experienced even as it’s less needed with Apple’s latest changes.