Learn how to use Disk Utility: RAID, pictures, and repairs

Use Disk Utility to maintain your Mac drives in line.

Disk Utility gives options for creating disk pictures, RAID, and repairing disks. Within the second a part of our deep dive, we’ll take a look at these choices.

Partly 1 of this sequence, we appeared on the fundamentals of Apple’s Disk Utility: what are units and volumes, how one can create and use volumes, and the way information and folders are saved on volumes.

This time, we’ll take a look at utilizing disk pictures, RAID, and repairing disks with Disk First Help.

Getting began with disk pictures

Disk Utility permits you to make actual copies of storage volumes and full units and retailer them as disk pictures. For Mac disks, these are normally saved as .dmg information utilizing Apple’s APFS or HFS+ filesystems.

Disk Utility and the Mac Finder additionally know how one can mount, copy, and format different disk picture codecs resembling .iso, FAT16 and FAT32, and exFAT codecs.

.iso pictures can solely be mounted on the Finder’s Desktop in the event that they have been formatted with a filesystem the Mac Finder is aware of how one can learn. Extra picture codecs might be supported by putting in third-party international file system plugins, which add extra filesystem assist to macOS.

For optical codecs resembling CD-ROM (Yellow Guide) and Compact Disc (Crimson Guide), Disk Utility makes .cdr pictures, however .cdr is absolutely simply .iso with an optical customary format utilized. The macOS Finder additionally is aware of how one can natively learn some prolonged CD-ROM codecs resembling CD-ROMXA, higher often called Picture CD.

In lots of circumstances you’ll be able to convert a .cdr Disk Utility picture to an .iso picture merely by altering its file extension to .iso – and typically vice versa.

You’ll be able to learn and save any optical format to a picture file utilizing Disk Utility, supplied it does not include a copy-protection scheme resembling these used on industrial DVDs or Blu-Rays.

Beware, nevertheless, that with a view to legally make disk picture copies of copyrighted supplies resembling audio CDs, you have to bodily personal the discs. You additionally should not share the copies with anybody with out the written permission of the copyright holders.

As soon as you’ve got made disk pictures of a quantity or machine, you’ll be able to later restore the quantity or machine utilizing Disk Utility’s Restore characteristic.

Sample disk images: two .dmgs, one .iso

Pattern disk pictures: two .dmgs, one .iso

Creating disk pictures

To make a disk picture of a quantity in Disk Utility, open the app within the Utilities folder in your Startup Disk, and choose a quantity from the volumes listing in Disk Utility’s essential window on the left facet, then Management-click or right-click.

Within the pop-up menu, “Choose “Picture from Quantity Title”, the place “Quantity Title” is the identify of the quantity you clicked on:

Control-click on a volume or device, then select

Management-click on a quantity or machine, then choose “Picture from” within the popup menu.

A normal file pane will seem, via which you’ll be able to give the file a reputation. Within the decrease proper nook is a Format menu, from which you’ll be able to select which type of disk picture to create:

  1. read-only
  2. compressed
  3. read-write
  4. DVD/CD grasp

Choose a location within the dialog the place you need to save the disk imag. Any storage location with sufficient area to carry the picture will work.

Learn-only pictures will mount on the Finder Desktop like actual volumes, however you will not be capable of write any information to them or modify current information on them.

Compressed pictures are like read-write pictures, however their information is compressed to make the disk picture smaller.

Learn-write pictures are the identical as read-only besides they’re absolutely writable when mounted on the Desktop. You’ll be able to write extra information to them, and modify current information on them.

If you unmount the read-write quantity, any modifications get saved into the disk picture.

DVD/CD grasp makes a precise bit-level copy of a CD-ROM, Compact Disc, or DVD disk. Once more, remember copying a DVD on this method will probably end in an unreadable copy because the copy safety scheme will not work on the copied information.

Not like the Compact Disc audio customary, DVDs have built-in copy safety to forestall piracy.

The identical authorized restrictions apply to copyrighted DVDs as apply to copyrighted CDs.

Give the image file a name, and select a format.

Give the picture file a reputation, and choose a format.

Within the Encryption popup menu under the Format menu, you’ll be able to optionally select 128-bit or 256-bit AES encryption. In case you select an encryption choice, all information on the quantity can be encrypted when the picture is created.

Click on the “Save” button to start creating the disk picture. You may be prompted by the Disk Utility helper device for a system admin password to start creation.

As Disk Utility creates the disk picture, a progress sheet will seem and, when accomplished, successful or error message can be displayed.

Notice that to ensure that the copy to start, Disk Utility has to unmount the quantity – or within the case of a tool, all volumes on the machine. If there are any open information on a quantity that must be unmounted, the copy will in all probability fail and you may see an error message within the Disk Utility progress sheet.

The result sheet - in this case, success.

The outcome sheet – on this case, success.

Notice that you may additionally make disk pictures of total storage units by following the identical process, however by first choosing “Present All Gadgets” within the View menu. You then Management-click on a tool in the principle listing within the Disk Utility window and choose “Picture From”.

Present All Gadgets causes Disk Utility to show not solely volumes however all of the bodily units containing these volumes. If you make a disk picture of a tool, you make a block-level picture of that machine – together with all of the volumes it incorporates.

After completion, you will have a brand new Disk Utility disk picture which is absolutely transportable, copyable, and might be mounted and unmounted at will on any Mac by double-clicking the picture file within the Finder.

To unmount a mounted disk picture in Finder, drag its quantity icon to the Trash within the Dock, or Management-click it within the Finder and choose “Unmount” or “Eject” from the popup menu.

Volumes containing open information or apps cannot be unmounted till all open information on them are first closed.

When the Finder mounts a quantity from a disk picture, Disk Utility additionally makes word of it utilizing file notification providers constructed into macOS. Disk Utility will listing all mounted disk picture volumes on the backside of the volumes listing on the left-hand facet of the window.

You’ll be able to Management-click any disk picture quantity proven right here and use the context popup menu simply as you’ll on any quantity on an actual machine.

The truth is, Disk Utility additionally creates a digital storage machine above every mounted quantity named “Apple Disk Picture Media” so as to use the context menu on it as if it have been an actual machine:

A virtual disk image device.

A digital disk picture machine.

You can too unmount volumes from the volumes listing by Management-clicking them and choosing “Unmount”. To take away the digital machine containing the quantity, Management-click it and choose Eject.

Restoring from disk pictures

Upon getting a disk picture, you’ll be able to restore it to a bodily machine pretty simply.

To take action, nevertheless, you have to first scan the picture to revive from through the “Pictures” menu in the principle menubar. To take action choose “Pictures->Scan Picture for Restore”, and when the usual file pane seems, choose the disk picture and click on “Scan”:


Choose “Scan Picture For Restore…” from the Pictures menu.

This enables Disk Utility to test the picture and confirm it may be restored to a tool or quantity.

As soon as the picture has been efficiently scanned, choose a quantity or machine from the principle listing within the Disk Utility window and click on the “Restore” button within the toolbar. This shows the Restore sheet:

The Restore sheet.

The Restore sheet.

Notice that this can be a little counter-intuitive: as an alternative of choosing the picture you need to restore first, you choose the machine or quantity you need to restore to first. As soon as the sheet seems, you’ll be able to then restore from the scanned picture by clicking the “Picture…” button.

You can too restore to any machine or quantity in your Mac by clicking the quantity popup button on the left of the “Picture…” button and choosing any current quantity. This lets you make a precise block-level copy of any quantity to every other quantity.

Use the Restore characteristic with care, since as quickly as you click on the Restore button within the lower-right nook of the sheet, all current information on the goal quantity or machine can be irrevocably destroyed.

As soon as the restore begins, Disk Utility will show a progress sheet, and when accomplished, whether or not the restore succeeded or failed. If it succeeded, Disk Utility will try to mount the restored quantity on the desktop.

You can too restore by Management-clicking in the principle listing within the Disk Utility essential window.

There are just a few different choices within the “Pictures” menu in the principle menubar:

  1. Confirm
  2. Add Checksum
  3. Convert
  4. Resize

“Confirm” permits you to confirm current disk pictures, and “Convert” permits you to change an current disk picture into any one of many different 4 codecs initially talked about on the high of this text.

Disk First Help

Disk First Help, or DFA as it’s higher identified, has been round on the Mac since System 6 within the late 1980’s. With Disk First Help, you’ll be able to scan a tool or quantity for issues and attempt to repair these issues if the device can.

On trendy Macs, this contains scanning a tool’s partition map and evaluating it in opposition to any discovered partitions on the machine to verify they match. There’s additionally the scanning of every quantity’s quantity header, catalog, and extents information to verify there are not any file or folder discrepancies.

On high of that, there’s the checking of UNIX permissions, house owners, and teams to verify the filesystem settings on system information are what they’re anticipated to be.

If Disk First Help finds any issues with a quantity or any broken volumes on a tool, it tries to restore them with a view to make them usable once more.

Besides within the case of repairing broken quantity constructions that forestall a quantity from mounting, Disk First Help does not normally recuperate any information on volumes straight. Apple additionally has a technote on how one can try to restore a Mac disk utilizing Disk Utility.

The original DFA.

The unique DFA.

To restore a quantity in Disk First Help, choose it from the principle window’s sidebar, and click on the “First Help” toolbar button, or Management-click the quantity in the principle window, and select “Run First Help” from the popup menu.

Click on the affirmation button within the alert, and Disk First Help will start checking the quantity for errors. If it finds any, it should try to restore them.

When the restore is completed, Disk First Help shows a sheet with a textual content abstract of what it discovered and what it repaired, if something.


Click on “First Help” or “Run First Help…” within the context popup menu.

You can too run First Help on bodily units along with volumes.

In case you’re repairing an APFS disk that incorporates a number of volumes, you need to run First Help on them in reverse order: restore volumes first, then container volumes, then disks. For extra data, see Apple’s technote on the subject.

Command line

Disk First Help depends on a number of command line instruments constructed into macOS: specifically hdutil, diskutil, and dd. To get extra data on any of those instruments, run their corresponding man pages in Terminal. For instance:

man diskutil and press Return.


A striped Redundant Array of Unbiased Disks (RAID) can permit big efficiency enhancements by marshaling drive information to and from a number of drive mechanisms concurrently. The elevated throughput unfold throughout disks quickens I/O and makes total entry quicker whereas presenting all the array to the pc as if it was one drive.

With drive costs pretty low as we speak, it is simple and cheap to arrange your personal RAID utilizing a number of drives.

Typically, you need to use the quickest exterior connection doable for RAID, resembling Thunderbolt. USB will work too – you simply will not see as large a efficiency enchancment over USB and you’ll with a Thunderbolt RAID.

A number of third-party distributors promote RAID-enabled drive enclosures that are easy to arrange and use.

Checking S.M.A.R.T standing

Self-Monitoring, Evaluation, and Reporting Know-how (S.M.A.R.T.)is a storage customary for monitoring drive well being on drives that assist it. Most trendy SSDs and exhausting drives have S.M.A.R.T. constructed into their firmware contained in the drive.

Commonplace SATA instructions are used to question the S.M.A.R.T. standing of a drive. Disk Utility is aware of how to do that routinely so there’s nothing you might want to do to test S.M.A.R.T. standing.

Some exterior USB drives do not report their S.M.A.R.T. standing as a result of the controller boards present in these drives do not assist translating S.M.A.R.T. instructions from the SATA drive mechanism to USB.

To learn a supported drive’s present S.M.A.R.T. standing, begin by drives and volumes in Disk Utility’s essential listing, then choose any machine within the listing. Make sure that to pick a bodily machine and never only a quantity.

If the drive helps S.M.A.R.T., Disk Utility will show its standing within the textual content grid in the principle window to the suitable of the machine listing, below the machine’s identify:

S.M.A.R.T. status in the main window.

S.M.A.R.T. standing in the principle window.

There are just a few different choices we did not cowl on this article resembling changing, including, and eradicating current APFS volumes, turning journaling on and off, and including checksums. We’ll deal with these partly 3.

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