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Apple Computing Products:
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How to monitor disk writes
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<blockquote data-quote="MacInWin" data-source="post: 1903719" data-attributes="member: 396914"><p>I'm not sure what you mean by "manually" but the way M1 Macs install/reinstall is entirely different from the old Intel systems. The system is stored in a Sealed System Volume (SSV) within the System-on-a-chip (SoC) that users cannot get to with any tools. It's completely hidden from all users and every tool out there. Only an Apple-signed process can get to the SSV. Apple installs the system in SSV, then does a series of encryptions/hashtagging to get hashtags for every file, folder and the entire system. Once that is calculated, the Mac contacts the Apple servers to compare the results with the master version, and if they agree, the volume is Sealed. That then becomes the master copy for that machine. When an update or upgrade comes along, the installer has the security embedded to unlock the seal and decrypt the system files, then apply the changes and recalculate all of the hashes. Once it again compares what is installed to what is the master record at Apple, the volume is again sealed. Once it is verified and sealed, the system then makes a snapshot of that SSV, verifies the snapshot against the local SSV and the Apple master and the snapshot is then blessed to enable to boot. If you want to know what happens at boot, read this: <a href="https://eclecticlight.co/2020/12/09/what-happens-when-an-m1-mac-starts-up/" target="_blank">What happens when an M1 Mac starts up?</a> All changes to that machine are applied ONLY to the boot snapshot, never to the SSV, unless it comes with the Apple security key. </p><p></p><p>So, when a user needs to "reinstall" the OS, what happens is that the reinstall process checks the current snapshot hash with the master hash of the SSV, and if it doesn't match, replaces all of the system files with copies from the SSV, reverifies the hashes, blesses the snapshot to allow boot and then boots. If the user has installed on a newly formatted drive, it goes through the Welcome process. If the install was over the existing installation, it boots to the login screen. The only time an M1 has to download the system installer from Apple is if there is a update/upgrade that needs to change what is in the SSV. And even if the user triggers that action, the Mac won't execute it before it checks with Apple to see if what is in the SSV is, in fact, the latest version. And if it is, no download. If what is in the SSV gets "broken" the Mac won't boot until the SSV is fixed. Depending on what "broke" the SSV, that could mean a download and reinstall, a visit to the Apple store, or even a trip to the repair depot to be fixed.</p></blockquote><p></p>
[QUOTE="MacInWin, post: 1903719, member: 396914"] I'm not sure what you mean by "manually" but the way M1 Macs install/reinstall is entirely different from the old Intel systems. The system is stored in a Sealed System Volume (SSV) within the System-on-a-chip (SoC) that users cannot get to with any tools. It's completely hidden from all users and every tool out there. Only an Apple-signed process can get to the SSV. Apple installs the system in SSV, then does a series of encryptions/hashtagging to get hashtags for every file, folder and the entire system. Once that is calculated, the Mac contacts the Apple servers to compare the results with the master version, and if they agree, the volume is Sealed. That then becomes the master copy for that machine. When an update or upgrade comes along, the installer has the security embedded to unlock the seal and decrypt the system files, then apply the changes and recalculate all of the hashes. Once it again compares what is installed to what is the master record at Apple, the volume is again sealed. Once it is verified and sealed, the system then makes a snapshot of that SSV, verifies the snapshot against the local SSV and the Apple master and the snapshot is then blessed to enable to boot. If you want to know what happens at boot, read this: [URL="https://eclecticlight.co/2020/12/09/what-happens-when-an-m1-mac-starts-up/"]What happens when an M1 Mac starts up?[/URL] All changes to that machine are applied ONLY to the boot snapshot, never to the SSV, unless it comes with the Apple security key. So, when a user needs to "reinstall" the OS, what happens is that the reinstall process checks the current snapshot hash with the master hash of the SSV, and if it doesn't match, replaces all of the system files with copies from the SSV, reverifies the hashes, blesses the snapshot to allow boot and then boots. If the user has installed on a newly formatted drive, it goes through the Welcome process. If the install was over the existing installation, it boots to the login screen. The only time an M1 has to download the system installer from Apple is if there is a update/upgrade that needs to change what is in the SSV. And even if the user triggers that action, the Mac won't execute it before it checks with Apple to see if what is in the SSV is, in fact, the latest version. And if it is, no download. If what is in the SSV gets "broken" the Mac won't boot until the SSV is fixed. Depending on what "broke" the SSV, that could mean a download and reinstall, a visit to the Apple store, or even a trip to the repair depot to be fixed. [/QUOTE]
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