User level: Level 1 (20 points)Hello,
I discovered that in my preboot disk, in addition to the UUID of my current data disk (current OS: Sequoia 15.8), there is also a reference to an old installation (UUID no longer existing) of Sonoma.
I was asking if it is possible and safe to cancel it, it would seem to be a few GB
Thank you
Posted on Sep 22, 2026 7:57 AM
User level: Level 7 (27,833 points)Sep 22, 2026 10:00 AM in response to andrews111
There is no preboot "disk." There is a hidden preboot volume on the boot disk.
It is *possible* there may be a left-over preboot volume from a previous install or a failed install/upgrade. Preboot volumes are complex and connected to the Secure System Volume (SSV). I suggest not touching it. There is no way to know whether or not there are any links or relationships between them or if both are connected to the SSV.
User level: Level 10 (218,444 points)Sep 22, 2026 11:17 AM in response to andrews111
If you're still bothered by the preboot volume you might try the following:
1 - make sure you have a current and full Time Machine backup.
2 - boot into the Recovery volume (boot with the Command + R keys held down - Intel Macs) or (How to Boot a Silicon Mac into Recovery Mode).
3 - erase the the boot drive with Disk Utility and formate it to A{FS with GUID partition may.
4 - install the current version of the system.
5 - when booting up with the new system and the Migration Assistant opens select the user data, applications, system and network, privacy and security settings, system and network and other files and folders to be migrated to from the Time Machine backup to the new system.
That should get rid of that preboot volume glich.
Originally posted at discussions.apple.com/thread/256362723