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Can't boot from Time Machine backup anymore?

zorinlynx

zorinlynx

macrumors G3
Original poster
May 31, 2007
8,391
18,853
Florida, USA
As a test I did a Time Machine backup of my Big Sur test laptop, then tried to boot from it and it didn't show up as a boot device.

In the past this has worked and it lets you very quickly restore a backup onto a new system. This restore was super convenient; it would restore whatever OS version was running on the old machine along with all the data.

Is this not something that's going to be supported anymore? That would be a shame, especially at work where we upgrade faculty Macbooks by doing a Time Machine backup and restoring it onto the new machine.
 
TM still uses HFS+, because it uses hard links which APFS does not support.

I assume Big Sur will only boot off an APFS disk.
 
zorinlynx said:
As a test I did a Time Machine backup of my Big Sur test laptop, then tried to boot from it and it didn't show up as a boot device.

In the past this has worked and it lets you very quickly restore a backup onto a new system. This restore was super convenient; it would restore whatever OS version was running on the old machine along with all the data.

Is this not something that's going to be supported anymore? That would be a shame, especially at work where we upgrade faculty Macbooks by doing a Time Machine backup and restoring it onto the new machine.
Click to expand...
I recommend you report this to Apple ASAP (as a bug). We have no idea if Apple intentionally remove this function. Or it's a real bug.
 
junkw said:
I never had one of my TM backups bootable? That's why I always used CCC for bootable drives
Click to expand...
I don't think CCC can make bootable clone of Big Sur yet.

Anyway, TM Backup is bootable. It depends on how you connect the TM drive.
OpenCanopy - Big Sur.png
 
I did some more investigation today, and no, I don't think Big Sur Time Machine backups disks are bootable.

In Catalina there is a checkbox in Time Machine settings, "Exclude system files and applications". That checkbox is gone in Big Sur.

In Catalina if you don't check this, a time machine backup will contain both the "Macintosh HD" system volume and the "Macintosh HD - Data" user data volume. In Big Sur, which doesn't have the checkbox anymore, a Time Machine backup only contains the "Macintosh HD - Data" volume. It's not bootable and you can't restore the entire system from it.

Maybe those of you who still see it as bootable are "continuing" a time machine backup from your previous Catalina install?
 
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