![]() The most common application scenes of disk images are system backup and computer deployment. With the development of floppy disks and external hard drives, more and more users tend to create disk images as a way of troubleshooting and problem prevention. ISO images can be created with almost any disk-burning software and can be opened on Windows, macOS, and Linux. ISO 9660 images are used to store data on optical discs such as CD-ROMs and DVD-ROMs. The most common disk image format today is ISO 9660, also known as CDROM or CDFS. An Apple disk image file's name usually has ".dmg" as its extension, and it is still used today on macOS, and this Apple-created disk images can be opened on Windows with third-party software. In 1996, Apple introduced the Apple Disk Image format with the release of Mac OS 8.0. CIF was used by Microsoft's DoubleSpace disk compression utility, which was bundled with MS-DOS 6.0. One of the earliest disk image formats was the Compressed Disk Image Format (CIF), which Microsoft developed in the early 1990s. History of Disk Imageĭisk images have been around for many years. This can be useful for testing or running software that is incompatible with your host operating system. A disk image can be loaded into a virtual hard disk (VHD), such as VMware or VirtualBox, and will behave just like a real disk. This can be useful if you need to restore your system to a previous state, as all data will be exactly as it was at the time the image was taken.ĭisk images can also be used to create virtual machines. It means that all disk data and even the structure information at the time the image was created will be included in the image. When you create a disk image, you take a snapshot of the entire disk or partition. Once this is patched, we can use whatever OS.A disk image is an exact copy of a disk or partition. Disk images are often used for backup purposes. However, if we ignore this limitation, we can actually use the Apple Silicon shared cache, and even boot it on Intel with some tinkering.ĭiscovered originally by ASentientBot, we can skip the OS.dmg verification by forcing _authenticate_root_hash inside of APFS.kext to return 0. The AMD graphics stack for example uses explicit x86_64h binaries, completely breaking pre-Haswell machines from using AMD GPUs natively. Now that we know the legacy cache still exists, does this mean we can boot Ventura on pre-Haswell hardware? The answer is kinda…Īt the time of writing, most of Apple’s kernel space does not explicitly use Haswell-only code paths. So even though Apple removed pre-Haswell support on Intel, they’re forced to keep it unless they plan to give Rosetta some work. ![]() However, if we look at the Apple Silicon disk image, it still has the non-Haswell cache? Well, this is due to a limitation in Rosetta 2’s current implementation, where it cannot emulate/translate AVX2.0 code. This is due to Apple removing the pre-Haswell support with Ventura. Apple Silicon Installįrom these 2 disk images, we can see that the Intel install is quite trimmed down. ![]() When you boot the OS, Apple will now mount the OS.dmg at /System/Volumes/Preboot/Cryptexes/OS/, and will be seen as a pseudo-overlay to the root volume. As mentioned with “Rapid Security Response”, the dyld now resides in the Preboot as a disk image labeled OS.dmg. Now with macOS Ventura, let’s take a peek at how they organize themselves. These dyld caches can be found under /System/Library/dyld/.Whereas with Intel, you can easily fit into one of the 2 camps. Here we see that Apple Silicon/Rosetta currently requires the x86_64 cache when it wants to translate Intel binaries. Used by pre-Haswell Intel CPUs, as well as Rosetta 2.When we look at Monterey’s dyld shared cache, we’ll see 3 different architectures supported: So a question you might be wondering is why were there 3 different dyld shared caches in Monterey and below on a single system? Their marketing term for this is Rapid Security Response, though we’re unlikely to see this active until after the fall release. This move additionally allows Apple to more easily handle security updates, as the Signed System Volume is no longer modified to perform general userspace updates.This allows for Apple to no longer ship 3 different dyld shared caches, saving the user precious disk space. One of these changes was moving the dyld shared cache off the root volume and inside the Preboot volume. Some of these techniques included removing on-disk kernel extensions, as well as adding more architectural-specific differences between Apple Silicon and Intel Macs. With the unveiling of macOS Ventura a few weeks ago, Apple did a full clean house on their root volume to try and remove as much bloat in their OS as possible.
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