Boot ROM
Jun 25, 2019 Recover macOS caches folder, log files, Library folders automatically If your data has been permanently deleted and you don’t have a backup from which you can recover it, the most reliable option to restore them is to opt for the secure and reliable Mac Data Recovery software. Rather than exhaustively list the possible names and locations for Adobe font caches, it is simpler to use the Find feature of the Mac OS X Finder to locate these files for you, then delete them. The following steps set up the Finder so you can locate files in System folders that are not normally included in Find operations. The first, is that you cannot be sure of the files to delete and which to leave. Restore keychain from library mac. There is the risk that if you delete some caches the Mac may crash, or you may encounter frequent system freezes. The space the caches takes up is also extremely unclear and deleting some files may have no impact whatsoever on the Mac’s speed.
When the power to a Macintosh computer is turned on, the BootROM firmware is activated. BootROM (which is part of the computer’s hardware) has two primary responsibilities: it initializes system hardware and it selects an operating system to run. BootROM has two components to help it carry out these functions:
How to find library folder mac high sierra. In the Terminal window, enter 'open library'. The library opens in a Finder window.To permanently show all hidden files:. Enter 'Terminal'. Click the Spotlight Search icon in the upper right corner.
Is it safe to delete the file Caches, in the Library of the Mac OS X Hard Drive? It's a pretty big file, 3.56 GB, Caches reminds me of logs i don't need or browser cookies. Is it safe to delete. The caches in /System/Library/Caches are generally small and useful, the ones in /Library/Caches are less system caches and much more readily cleared. If you have a look in /Library/Caches you will find a bunch of applications have a cache in there, none of them particularly large though dropbox sometimes has a fair sized cache. Nov 09, 2019 1. Based on the information you shared before, your Mac OS is Catalina 10.15. Try upgrading to Mac OS Catalina Developer Beta 6 to see if the issue persists. At the same time, you can temporarily disable the proxy and firewall to test this issue.
- POST (Power-On Self Test) initializes some hardware interfaces and verifies that sufficient memory is available and in a good state.
- EFI does basic hardware initialization and selects which operating system to use.
If multiple installations of OS X are available, BootROM chooses the one that was last selected by the Startup Disk System Preference. The user can override this choice by holding down the Option key while the computer boots, which causes EFI to display a screen for choosing the boot volume.
The Boot Loader
Once BootROM is finished and an OS X partition has been selected, control passes to the boot.efi boot loader. The principal job of this boot loader is to load the kernel environment. As it does this, the boot loader draws the “booting” image on the screen.
If full-disk encryption is enabled, the boot loader is responsible for drawing the login UI and prompting for the user’s password, which needed to access the encrypted disk to boot from it. (This UI is drawn by
loginwindow
otherwise.)In the simplest case, the boot loader can be found in the
/System/Library/CoreServices
directory on the root partition, in a file named boot.efi
.Note: Booting from a UFS volume is deprecated as of OS X v10.5.
In order to speed up boot time, the boot loader uses several caches. The contents and location of these caches varies between versions of OS X, but knowing some details about the caching may be helpful when debugging kernel extensions.
After you install or modify a kernel extension, touch the
/System/Library/Extensions
directory; the system rebuilds the caches automatically.Important: You should not depend on the implementation details of the kernel caches in your software.
In OS X v10.7, the boot loader looks for the unified prelinked kernel. This cache contains all kernel extensions that may be needed to boot a Mac with any hardware configuration, with the extensions already linked against the kernel. It is located at
/System/Library/Caches/com.apple.kext.caches/Startup/kernelcache
.In OS X v10.6 and earlier, the boot loader first looks for the prelinked kernel (also called the kernel cache). This cache contains exactly the set of kernel extensions that were needed during the previous system startup, already linked against the kernel. If the prelinked kernel is missing or unusable (for example, because a hardware configuration has changed), the booter looks for the mkext cache, which contains all kernel extensions that may be needed to boot the system. Using the mkext cache is much slower because the linker must be run. On OS X v10.5 and v10.6, these caches are located in
/System/Library/Caches/com.apple.kext.caches/Startup/
; on previous versions of OS X, it was located at /System/Library/Caches/com.apple.kernelcaches/
.Finally, if the caches cannot be used, the boot loader searches
/System/Library/Extensions
for drivers and other kernel extensions whose OSBundleRequired
property is set to a value appropriate to the type of boot (for example, local or network boot). This process is very slow, because the Info.plist
file of every kernel extension must be parsed, and then the linker must be run.For more information on how drivers are loaded, see IOKit Fundamentals, the manual page for
kextcache
, and Kernel Extension Programming Topics.Rooting
Once the kernel and all drivers necessary for booting are loaded, the boot loader starts the kernel’s initialization procedure. At this point, enough drivers are loaded for the kernel to find the root device.
The kernel initializes the Mach and BSD data structures and then initializes the I/O Kit. The I/O Kit links the loaded drivers into the kernel, using the device tree to determine which drivers to link. Once the kernel finds the root device, it roots(*) BSD off of it.
Note: As a terminology aside, the term “boot” was historically reserved for loading a bootstrap loader and kernel off of a disk or partition. In more recent years, the usage has evolved to allow a second meaning: the entire process from initial bootstrap until the OS is generally usable by an end user. In this case, the term is used according to the former meaning.
As used here, the term “root” refers to mounting a partition as the root, or top-level, filesystem. Thus, while the OS boots off of the root partition, the kernel roots the OS off of the partition before executing startup scripts from it.
Boot≠Root is a technology that allows the system to boot from a partition other than the root partition. This is used to boot systems where the root partition is encrypted using full-disk encryption, or where the root partition is located on a device which requires additional drivers (such as a RAID array). Boot≠Root uses a helper partition to store the files needed to boot, such as the kernel cache. For more information on how to set up the property in a filter-scheme driver, see Developing a Filter Scheme in Mass Storage Device Driver Programming Guide.
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