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by Tom Nelson

Dashboard, the secondary desktop introduced with OS X Tiger, is gone, vamoosed, kaput; it’s an ex-desktop. With the advent of macOS Mojave, the Dashboard and all of those productive widgets are gone. Such is the penalty paid for progress. Or is it?

If you’re a fan of Dashboard and all of its funky widgets, such as weather, an assortment of clocks, a calendar, local movie listings, stocks, and whatever else you may have loaded into the Dashboard environment, the good news is that the Dashboard isn’t really gone, Mojave just turned it off by default.

Now, having Dashboard disabled by default may be an indication of what is in store for Dashboard down the road. Dashboard widgets, those mini applications, haven’t seen a lot of activity from developers in quite a while, and most of the widgets can be replaced with apps from the Mac App Store. And if rumors are to be believed, some iOS apps, beyond those included with Mojave, may in the future make the jump to macOS. In that case, the Dashboard environment may just not make a lot of sense anymore. But that doesn’t mean you can’t still enjoy it for now.

Enabling the Dashboard
It’s an easy process to turn Dashboard back on:

Use the Mission Control preference pane to enable Dashboard, as well as to select what mode it will operate in. Screen shot © Coyote Moon, Inc.

Launch System Preferences by clicking or tapping its icon in the Dock, or selecting System Preferences from the Apple menu.

Select the Mission Control preference pane.

Locate the dropdown menu next to the Dashboard text.

Use the dropdown menu to select one of the following:

  • Off: The default state for Mojave. The Dashboard is turned off and can’t be used.
  • As Space: The Dashboard environment is treated as a separate desktop space. You can switch into and out of the Dashboard space using the Spaces bar, keyboard shortcuts, or gestures.
  • As Overlay: This is the classic method of displaying the Dashboard, as an overlay above your normal desktop.

Make your selection from the dropdown menu.

You can now quit the System Preferences.

Accessing the Dashboard
There are a number of ways to access the Dashboard, though the most common is to use the F12 or the Fn + F12 keys (depending on the keyboard type you’re using). Pressing the F12 key will either display the Dashboard as a space that slides into place, replacing the current desktop or other active space, or as an overlay on top of the current desktop.

There are additional ways to access the Dashboard once you have turned the feature on:

Launch the Mission Control preference pane, as you did earlier.

In the Keyboard and Mouse Shortcuts section, you can assign keystrokes or mouse buttons to perform specific tasks. Look for the Show Dashboard text. Next to the text are two dropdown menus; the first can be used to assign any of the function keys, F1 through F19 (your keyboard may not have all 19 function keys). You can also use the Shift, Control, or Command keys in combination with the function keys to create up to 57 possible key combinations to access the Dashboard.

If you would prefer to use your mouse, the second dropdown menu to the right allows you to select from up to seven different mouse buttons to use to access the Dashboard environment.

Hot Corners allows you to access the Dashboard by moving the cursor into the designated corner. Screen shot © Coyote Moon, Inc.

Hot Corners are another way to access the Dashboard. With this method, simply moving the cursor to one of the corners of your display can cause the Dashboard to appear. To set up Hot Corners, click the Hot Corners button in the Mission Control preference pane. In the sheet that drops down, select the dropdown menu that corresponds to the display corner you wish to use, and then select Dashboard from the dropdown menu’s list of options.

You can also use the Dock to work with Dashboard. Click or tap the Dashboard icon in the Dock to go directly to the Dashboard. Chances are there’s no Dashboard icon in your Dock under Mojave, but it’s easy to put it back. In the Finder, open the Applications folder, and then drag the Dashboard app to the Dock.

Prefer to use gestures? That’s possible as well:

  • Dashboard enabled as a space: You can use the standard two-finger swipe left or right to move between spaces.
  • Dashboard set as an overlay: You can use a three-finger swipe up to open Mission control, and then select the Dashboard from the Spaces bar.

Quit Dashboard
To quit the Dashboard and return to the desktop:

  • Press the Escape key.
  • Press the arrow icon in the bottom right corner of the Dashboard.
  • When Dashboard is used as an overlay, click or tap in any empty space of the Dashboard.

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by Tom Nelson

Once a popular option in the early days of the Mac, RAM disks, which were used to speed up the performance of a Mac, have fallen by the wayside.

Conceptually, RAM disks are a simple idea: a chunk of RAM set aside that looks, to the Mac system, like just another storage drive. The system, as well as any installed apps, can write files to or read files from the RAM disk, just as if it really were another storage drive mounted on your Mac.

But unlike any storage drive, a RAM disk can operate at the speed of RAM, which is usually many times faster than most drive storage systems.

RAM Disk History
RAM disks existed before the Macintosh ever hit the market, but we’re going to predominantly explore how RAM disks were used with the Mac.

The Mac Plus, released in 1986, had quite a few new features, including the use of SIM (Single Inline Memory) modules that users could easily upgrade. The Mac Plus shipped with 1 MB of RAM, but users could increase the memory size to 4 MB. That was an amazing amount of RAM in 1986, and begged the question: What can I do with all this memory space?

At the same time, many users were asking how they could speed up their Macs. And while many users were happy to just max out the RAM, and enjoy the performance gain of having more memory, which let them run more applications concurrently, some users discovered the joys of using a RAM disk to speed up the system and apps. Other users discovered that a RAM disk could be used to create an amazingly fast storage system. Remember, back then, most Mac Plus users were getting by with a single 800 KB floppy drive, while those who felt like splurging could add an additional external floppy drive. If you really had cash to burn, you could hook up a 20MB SCSI (Small Computer System Interface) hard drive, which would likely set you back well over $1,200.

The first prominent use of a RAM disk was to copy the Mac’s slow ROM (Read Only Memory), which contained many of the system’s core components, along with the operating system, which was stored on a floppy drive, and move them both to a RAM disk where they could operate at the speed of RAM; many, many times faster than either the floppy disk or the ROM.

The performance increase was amazing, and was achieved for just the cost of a RAM disk utility app.

The second common use of a RAM disk back in the Mac Plus days was to create a tiered storage system. Floppy drives weren’t fast enough for professionals or avid amateurs to work with new rich media editing systems, such as audio editors, image editors, or page layout apps. SCSI drives could meet the needs of image editing and page layout, but audio editing was at best iffy, with most SCSI drives being too slow to provide the needed bandwidth for audio or other real-time editing.

RAM disks, on the other hand, were very fast, and could easily meet the needs of real-time editing with their ability to write or read files as quickly as the RAM could be accessed, without the mechanical latency inherent in SCSI or floppy disks.

RAM disks can be very fast. In my case, over 10x faster than my Mac’s startup drive. Screen shot © Coyote Moon, Inc.

The only disadvantage to RAM disks was that the data stored in them was lost every time you turned your Mac off, or the power went out. You had to remember to copy the content of the RAM disk to your main storage system or your work would be lost.

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by Tom Nelson

Originally introduced with OS X El Capitan, System Integrity Protection, usually referred to as SIP, is a security feature built into the Mac operating system that’s designed to protect most system locations, system processes, and Kernel extensions from being written to, modified, or replaced.

SIP and related security protections in the Mac operating system have undergone changes with each release of the OS, but the basics of how the SIP system works have remained the same, including how SIP can be enabled, disabled, and have its current status checked on.

Rootless, More or Less
OS X El Capitan was the first version of the Mac operating system to incorporate SIP, as well as the idea that the Mac operating system was now rootless; that is, there was no longer a root account, the all-powerful primary account that had access to almost the entire system. But it turns out the concept of the Mac being rootless was more of a security marketing gimmick than actual fact. There was still a root account; the difference is that when enabled, SIP poses additional restrictions on the root account, walling off certain portions of the system from access by an account with root level privileges.

The additional isolation of system components from accounts with root privileges helps to prevent malware from being able to gain access to the system, where it could embed itself and take advantage of all of the system services running on a Mac.

System Integrity Protection (SIP)
While “rootless” was mostly marketing, SIP actually hardened the Mac by preventing modifications to the following locations:

  • /System
  • /usr
  • /bin
  • /sbin
  • All apps preinstalled by Apple

The exceptions to the rule are apps or processes that have been signed by Apple and have special entitlement to write to system files. This includes Apple installers and Apple software update services.

SIP is effective at stopping system locations from being written to by third-party apps and services. Only Apple-signed system processes can write to system locations.

System processes can’t be attached to. This prevents code injection or runtime attachment to system processes, techniques often used by malware to force privileged processes to run the malware code.

Kernel extensions must be signed with an Apple Developer ID that specifically allows for signed Kext (kernel extensions) certificates. This can prevent kernel extensions from being replaced or modified by malware, as well as prevent new unsigned kernel extensions from being installed.

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by Tom Nelson

Disk Utility, the macOS Swiss Army knife for working with disks and storage volumes, may have a few blades missing, especially when it comes to working with unformatted drives and unused space on a disk or storage volume.

In versions of Disk Utility that came with OS X Yosemite and earlier, you could enable hidden debug modes in the Disk Utility app that allowed you to see and interact with all the space on a disk, including hidden elements, such as the Recovery volume or the secret EFI partitions.

In this Rocket Yard article, we’re going to look at how to enable Disk Utility to view and work with the types of disk spaces you’re likely to encounter, including:

We’ll also demonstrate how to use Terminal to access the remaining hidden disk structures that Disk Utility can’t view directly, including:

  • Recovery volumes
  • EFI volumes
  • Preboot and Boot volumes

Selecting the Initialize button will open Disk Utility, but the disk may not show up if the apps view settings are in the default settings. Screen shot © Coyote Moon, Inc.

Using Disk Utility to Access All Devices
Disk Utility is configured by default to only show formatted volumes. This makes using Disk Utility with existing volumes an easy task since there are only a few, and sometimes only one, volumes displayed, cutting down on what could be an overwhelming list of disks, containers, volumes, RAID slices, etc.

The disadvantage, however, is that it can make it difficult to work with new unformatted disks you may be using for the first time. This includes working with unformatted drives as well as unformatted USB flash drives.

Tip: When we speak of unformatted drives, we’re including any disk that uses a format that your Mac can’t natively work with.

Disk Utility lets you pick which display mode to work in: Volumes only, All Devices, or only a selected drive. You can switch between them at any time, and Disk Utility will update the display immediately; no need to close and reopen the Disk Utility app or restart your Mac.

Show All Devices
This setting will display all storage devices connected directly to your Mac. In addition to each device being displayed, a hierarchical listing will show how each device is organized, i.e., how many containers, partitions, or volumes each device contains. Absent from the hierarchical view will be any of the items Apple has decided to hide from the end user, such as EFI volumes and Recovery volumes.

When Disk Utility’s view option is set to Show All Devices even unformatted devices will be present in the sidebar, such as the highlighted USB flash drive that needs to be formatted. Screen shot © Coyote Moon, Inc.

From the Disk Utility toolbar, click the View button, and then select the Show All Devices item from the dropdown menu. You can also select Show All Devices from Disk Utility’s View menu.

The Sidebar will change to display all locally connected devices, presented in a hierarchical view starting with the physical device, than any containers and volumes the device may have been partitioned into.

Hide the Sidebar
For the ultimate in simplicity, you can choose to hide the sidebar and remove any listings of devices or volumes from view.

From the Disk Utility toolbar, click the View button and select the Hide Sidebar item in the dropdown menu. You can also select Hide Sidebar from Disk Utility’s View menu.

The sidebar will close, and the last selected item in the sidebar will become the only item listed in the Disk Utility window.

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by Tom Nelson

You may not have heard of rsync; it’s a file transfer and synchronization program that’s often used to create elaborate and complex backup systems.

Written for Unix operating systems, rsync is included with the Mac and can be accessed directly from Terminal, or used within a number of scripting languages.

The rsync program has a number of features that make it a good candidate for building local, as well as remote, backup, archiving, and synchronization systems. It can also be used for basic file copying, and for maintaining file synchronization between one or more folders, either locally or with a remote system (think cloud-based storage, as an example).

In this Rocket Yard Guide, we’re going to concentrate on using rsync locally. If you wish to use rsync with a remote system, you’ll need to ensure that both the local system and the remote system have rsync installed.

If you’re looking for a copy of rsync to install on a system other than a Mac, or you’re just interested in discovering more about this versatile app, you can check out the rsync website.

Before we get into details about using rsync on the Mac, a note about versions. The version of rsync that’s distributed with the Mac tends to lag behind the current version available on the rsync website. The Mac version has been at 2.6.9 for a number of years, while the current version is at 3.1.3 (as of January, 2018). You should have no problems using the older Mac version with remote platforms that have one of the newer versions installed, but going the other direction could have unexpected results. Always check version compatibility when using rsync with remote systems.

Using Rsync
The Terminal app is used to invoke rsync and its various commands. If you’re new to using the Terminal app, check out the Rocket Yard series Tech 101: Introduction to the Mac’s Terminal App.

Rsync uses a simple structure for issuing commands:

rsync -options theSourceDirectory theDestinationDirectory
While the number of options can get long, the format is always the same; the rsync command followed by any optional switches, then the source directory followed by the destination directory.

The rsync -r command copied all the files on my Desktop to my USB flash drive named DocsBackup. Notice that the time stamp on all the copied files is set to the current date. Screen shot © Coyote Moon, Inc.

Let’s look at a basic rsync command that will copy a directory and all sub-directories it may contain. To tell rsync we want all the files and folders, including everything in subdirectories, we include the -r option. In the Terminal app, enter:

rsync -r /Users/tnelson/Desktop /Volumes/DocsBackup

(Replace tnelson with your user name, and DocsBackup with your desired target for the copy.)

In this example, my messy Desktop folderand its contents will be copied to a USB flash drivenamed DocsBackup. After the command is executed by hitting the return or enter key, the DocsBackup flash drive will have a new folder named Desktop, with all of my Desktop content.

If you want to copy only the contents of the Desktop, and not the parent folder named Desktop, you would add a forward slash after the directory named Desktop, like this:

rsync -r /Users/tnelson/Desktop/ /Volumes/DocsBackup

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by Tom Nelson

Disk First Aid, currently part of Disk Utility, has long been the go-to utility for verifying and repairing a Mac’s storage system. Included as a standalone app with the original Mac OS, it was later folded into Disk Utility when OS X was released.

Disk Utility, and its First Aid system remains the first line of defense for drives that are experiencing a number of issues, including:

  • System crashes
  • Files disappearing
  • File sizes changing on their own
  • Inability to copy files
  • Inability to open or save files
  • Startup issues
  • Drives unmounting or ejecting on their own
  • And a host of other errors and issues

In this guide, we’re going to take a look at using Disk Utility’s First Aid tool in macOS High Sierra to repair APFS and HFS+ file systems. First Aid can actually be used on any file system that macOS supports, but APFS and HFS+ are the most popular, and the ones you’re most likely to encounter.

We’ll start by going through the actual process of using First Aid, and then take a more in-depth look at the process; we’ll also provide a few troubleshooting tips.

Before you use First Aid, make sure you have a current backup of the drive or volume you’re having issues with. If you’re using First Aid as part of a routine maintenance program, you should still have a working backup of any volume that you’ll be checking.

The Disk Utility app underwent a few updates with the release of macOS High Sierra to support the APFS file system. If you’re working with OS X El Capitan through macOS Sierra, you may find the instructions in How to Use macOS Sierra Disk Utility to Verify or Repair Disks a better fit.

Disk Utility’s Sidebar in macOS High Sierra and Later
Launch Disk Utility, located at /Applications/Utilities.

Disk Utility’s default settings use a sidebar that only displays storage volumes. Since you may need to use the First Aid tool on volumes as well as partitions, catalogs, and physical devices, it’s a good idea to change the sidebar settings to display all devices.

The View button in Disk Utility’s toolbar will expand the sidebar to show all devices. Screen shot © Coyote Moon, Inc.

Click the View button in the Disk Utility toolbar and select Show All Devices from the popup menu, or select Show All Devices from the View menu.

The sidebar will now display all devices, including the physical drive and any APFS containers it may have, as well as any APFS or HFS volumes associated with the physical drive.

The organization of the devices is hierarchical, with the physical drive listed first, using the manufacturer’s name, or the model name or number, or both. At the next level under the physical drive is the Container (APFS file system), followed by the volumes. If this is an HFS-formatted drive, there won’t be any containers under the drive level, just volumes.

Each item can be selected and repaired using the First Aid tool.

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by Tom Nelson

Your Mac is full of secrets; special files and folders hidden away so you don’t accidentally make changes to critical system components. But Apple isn’t the only one that hides items on your Mac; some developers use similar tricks to keep important secret app files, such as licensing credentials, from being used willy-nilly.

You can get in on the secrets of hiding files and folders so that others can’t easily find them, or make use of their content, with just a few simple Terminal tricks.

Using Terminal to Hide a File or Folder
Terminal has always been a favorite app of mine, so much so that I keep it in the Dock for easy access. Terminal can be used to invoke a couple of commands that can be used to hide or unhide a file or folder.

You may have already made use of the Terminal chflags command to unhide the user’s library folder, which Apple hides by default. If you’re wondering about the user’s library, often written out as ~/Library, you can learn a bit more about it in the article: Access Your Hidden Library Folder With These Five Easy Tricks.

Use the Secrets folder to hide any files or folders you wish. Screen shot © Coyote Moon, Inc.

Let’s take a look at hiding a folder using Terminal by first creating a folder that we can hide.

Open a Finder window, and navigate to your home folder. You can do this by selecting your home folder from the Finder sidebar.

Within the home folder window, either right-click in an empty area and select New Folder from the popup menu, or select New Folder from the Finder’s File menu.

A new folder will be created, and the name (untitled folder) highlighted. Enter a new name for the folder, such as Secrets.

With the Secrets folder created, it’s time to make it disappear.

Launch Terminal, located in /Applications/Utilities, and arrange the Finder and Terminal windows so that you can see both of them.

In the Terminal window, enter the following at the prompt:

chflags hidden ~/Secrets

Hit the Enter or Return key.

The Secrets folder should disappear from the Finder window.

The Secrets folder wasn’t deleted; it simply had a flag changed that told the Finder not to display it in a Finder window. The folder is still right where you created it.

We can bring it back by typing a magic word or two in Terminal:

chflags nohidden ~/Secrets

Press Enter or Return.

The Secrets folder is back.

The first chflags command hides the folder named Secrets, while the second chflags command reveals the hidden Secrets folder. Screen shot © Coyote Moon, Inc.

That’s not the only Terminal method for making a file or folder disappear. You can also make a file or folder disappear by prepending a period to its name. If we change the Secrets folder name to .Secrets the folder will become invisible to the Finder.

Alternatively, you can use the Terminal mv command, which is designed to move a file or folder to a new location, but can also be used to change a file or folder name.

In the Terminal window, enter the following:

mv ~/Secrets ~/.Secrets

Press Enter or Return.

Just as before, the Secrets folder becomes invisible in the Finder.

You can make it visible again by using the mv command to remove the period from its name.

In the Terminal window, enter:

mv ~/.Secrets ~/Secrets

Hit Enter or Return.

The Secrets folder is now visible within the Finder.

The first mv command is used to hide the Secrets folder by adding a period at the front of its name. The second mv command removes the period and makes the Secret folder visible. Screen shot © Coyote Moon, Inc.

With both the chflags and the mv Terminal commands, you’re able to make a folder and all of its contents become invisible in the Finder. You can also use the same commands on a single file, if you wish. But since the Terminal commands we mentioned require knowing the pathname to the item, it’s a good idea to just use a single folder to hide one or more items within. That helps simplify the process of remembering the required pathname when it’s time to make the items visible.

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by Tom Nelson

The Mac App Store was supposed to be the place to find and purchase apps for a Mac without having to worry whether the seller, developer, or some other third-party had somehow tampered with the app for nefarious purposes. You also weren’t supposed to need to worry about the download sites being full of ads that could contain malware, ransomware, or other worrisome possibilities.

For the most part, the Mac App Store, along with the other Apple app stores, has lived up to this expectation of being a place where malware and deceptive practices don’t exist. For the most part…

Unfortunately, it’s still advisable to make use of the various stores with caution; not so much about the worry of malware being embedded within an app, though it may happen once in a while, but of scammers trying to acquire personal information by using the Apple stores as bait.

Email Scams Using the App Store as Bait
I just got an email phishing scam this week that pretended to be from Apple, warning me about a purchase I made on the Mac App Store that wasn’t made by a device that Apple recognized. I should, according to this email, use the included link and log in to a special section of the Mac App Store, where I would be asked to verify or cancel the purchase.

The Mac App Store has a reputation as a safe place to purchase Mac apps from, but that doesn’t stop scammers from using the Mac App Store as bait in phishing schemes. Screen shot © Coyote Moon, Inc.

What a load of hooey. This email had scam written all over it. Besides its use of long run-on sentences and other grammar faux pas, there were a number of other indicators that can be spotted in most of these email phishing expeditions. Apple even has a guide to help you identify legitimate emails from the App Store.

Another phishing scam making the rounds involves receiving a confirmation note about a subscription you purchased in one of the Apple stores. The text of these subscription scams all start by confirming a free trial subscription to a service, and notifying you that once the free trial is over, the monthly cost is an absurdly high amount. One current example is a subscription to YouTube Red, at a monthly cost of $144.99. The purpose of this type of scam is to get you to click on the Cancel Subscription link included in the email. Doing so will take you to a site where you’ll be asked to provide your Apple ID or credit card info, or both. Of course, there never was a subscription to the service, but playing on the fear of being billed will lead some people to click that cancel link.

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by Tom Nelson

AirDrop is a peer-to-peer file sharing system for local Mac and iOS users. It’s easy to set up with just a click or two; no special information or settings are needed. Just drag-and-drop a file to share with others.

In this Rocket Yard Guide, we’re going to take a look at AirDrop’s history, the basics of its use, and a tip or two for improving its use, including adding AirDrop to the Mac’s Dock for easy access.

AirDrop History
Originally developed for the Mac and released with OS X Lion, AirDrop made use of a new Wi-Fi standard called PAN (Personal Area Network) that allowed for the creation of an ad-hoc wireless network. To make setting up the network automatic, Apple made use of its Bonjour service, which allowed Macs to broadcast that they were part of the Wi-Fi network and could receive files from others.

When iOS 7 was introduced, it included its own version of AirDrop, but replaced the use of Bonjour with Bluetooth LE, and kept peer-to-peer Wi-Fi for sending and receiving, though it dropped the use of the PAN protocol.

When OS X Yosemite was released, it included support for both sets of AirDrop protocols, allowing supported Macs to use AirDrop with other supported Macs, as well as iOS devices.

Not all Macs or iOS devices are compatible with AirDrop. You can check this AirDrop support document to see if your Mac or device supports AirDrop.

Using AirDrop
AirDrop requires the use of either Wi-Fi or Wi-Fi and Bluetooth, depending on the version of AirDrop being used.

You can open an AirDrop Finder window by selecting AirDrop from the Finder sidebar, or from the Finder’s Go menu.

The AirDrop window displays nearby devices that have AirDrop enabled. Screen shot © Coyote Moon, Inc.

AirDrop appears as a special Finder window folder that displays any nearby Mac or iOS devices that have AirDrop enabled.

You can drag any file or folder onto a device listed in the AirDrop window. You can also use the share button within an app to send a file via AirDrop. Depending on the version of AirDrop being used, you may be asked to confirm that you wish to send a file to the selected user.

The destination device will display an alert, asking the user if they wish to accept the files being sent.

On the Mac, files being sent will appear in the Downloads folder, once accepted. On iOS devices, the files will be associated with specific apps, such as images being placed in the Photos app.

Can’t find one of your older Macs? Later versions of AirDrop changed the method used to detect AirPort-enabled devices. You may need to use the Search for an Older Mac option. Screen shot © Coyote Moon, Inc.

OS X Yosemite and later support both sets of protocols, but are set to Bluetooth LE/Wi-Fi as the default. To access older Macs, you must select the option to search for older Macs. This will reset the protocol to the older version, allowing you to connect with older Macs, but not with iOS or newer Macs using Bluetooth LE/Wi-Fi. In OS X Yosemite and later, you’ll find this option labeled “Don’t see who you’re looking for?” at the bottom of the AirDrop folder window. Clicking in this text will bring up the option to Search for an older Mac.

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by Tom Nelson

The Mac’s Disk Utility app supports a number of capabilities that make managing the Mac’s storage system easier. But one set of features seems to get overlooked a bit: the creation and management of encrypted disk images.

Disk images have many benefits; they can be used to distribute apps and data to users, for creating master image files for various media types, such as CDs and DVDs, and for creating archives and backups, as well as quite a few additional creative uses.

Encrypted disk images allow you to protect the content of the images from prying eyes. Encrypted disk images can’t be mounted, viewed, or accessed unless you know the password associated with the image file.

In this Rocket Yard Guide, we’re going to look at how to create encrypted disk images. We’ll start with an overview of the basics of disk images and encryption, and then show you how to actually create various types of disk images.

Encryption Type
Disk images support two types of encryption: 128-bit AES (Advanced Encryption Standard) and 256-bit AES. The two levels of encryption refer to the size of the keys used in the encryption/decryption process. The 256-bit encryption is considered more secure than the 128-bit encryption, but the 256-bit encryption also takes longer to encrypt and decrypt. The 128-bit encryption will likely meet the needs of most people, while the 256-bit encryption is a better choice for data that needs a higher level of protection.

Mounting an Encrypted Disk Image
Before you can make use of a disk image, it needs to be mounted, so your Mac can work with the data within it. Mounting an encrypted disk image isn’t much different than mounting a normal disk image; simply double-click the disk image file, or right-click (control-click) the disk image file, and select Open from the popup menu.

Before the image is mounted, your Mac will display a window that asks you to provide the password to grant access to the information stored within. Enter the password, and click the OK button.

You can also automate the task of providing the password by selecting the option to “Remember password in my keychain.” When this option is selected, either during the encrypted image file creation (OS X Yosemite and earlier), or when you’re asked for the password when mounting the image (all versions of the Mac OS), the password will be stored within your keychain and used automatically the next time you mount the image file.

Unmounting an Encrypted Disk Image
Unmounting an encrypted disk image returns the image file to an encrypted state, preventing access to the data stored within. You can unmount the image by dragging the mounted image (not the image file) to the trash, or right-clicking on the mounted image and selecting Eject from the popup menu.

Image Formats
Disk Utility supports creating a number of disk image formats that can be used for various projects. Not all of the following formats are available in every version of Disk Utility, or with every method of creating a disk image.

Disk Utility supports a number of image formats. The formats that are available can change with the version of the OS, and the method used to create a disk image. Screen shot © Coyote Moon, Inc.

Read only: Allows the content of the mounted image to be viewed, and any files it contains to be opened and read. Additions to the image or changes to any of the files are not allowed. The read only option is only available when creating an image from a folder or drive, or when converting from one image format to another.

Compressed: Similar to the read only option, but any free space within the image is first removed to reduce the size of the image file. The compressed option is only available when creating an image from a folder or drive, or when converting from one image format to another.

Sparse image: This type of image format allows the image size to grow and shrink, to accommodate the amount of data stored in the image. The maximum size the image can grow to is set during the image creation process. Sparse image files have the file extension: .sparseimage

Sparse Bundle disk image: This type of disk image is made up of multiple small files, usually 1 MB, 2 MB, 4 MB, or 8 MB in size. When data stored on this type of image is changed, only the file(s) that contains the changed data needs to be changed, created, or deleted. Just like the sparse image format, a sparse bundle disk image has a flexible size that grows or shrinks to accommodate the data within. The sparse bundle disk image is used extensively with Time Machine. Sparse bundle image files have the file extension: .sparsebundle

Read/Write disk image: This image format allows you to add files to the image after it is created. The size of the image file is predefined, and can’t be expanded or reduced once created. Read/Write image files have the file extension: .dmg

DVD/CD master: This image type is used for mastering CDs or DVDs. If you’re using OS X El Capitan or later, when this format is selected, the image size field will change to a dropdown menu with 177 MB (CD 8 cm) selected. You can use the dropdown size menu to select any of the standard DVD/CD sizes. If you’re using OS X Yosemite or earlier, you must manually change the size field to one of the standard DVD/CD sizes. DVD/CD images have the file extension: .cdr

Hybrid image (HFS+/ISO/UDF): This image format is used for creating a single image whose files can be used on multiple platforms.

Note: The two sparse image formats have a maximum size that you set during creation. This is the size the image file will appear to have when mounted on your desktop. The actual image file (the .sparsebundle or .sparseimage file) will only use the amount of space needed to hold the data within.

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