I have a MacBook Pro8,1. For experimental purposes I've installed Windows 7 to USB (it's NOT an installer, a real OS on USB) via WinNTSetup on other PC. When I'm trying to boot from the USB with the command (I've unmounted the disk before):
sudo bless --device /dev/disk3s1 --setBoot --legacy
It doesn't work – it just boots to Windows 10 installed on the internal HDD with legacy method + Hybrid MBR too.
Here's my partition table:
/dev/disk0 (internal, physical): #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *500.1 GB disk0 1: EFI EFI 209.7 MB disk0s1 2: Apple_HFS HDD 379.8 GB disk0s2 3: Microsoft Basic Data BOOTCAMP 119.9 GB disk0s3 /dev/disk1 (internal, physical): #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *128.0 GB disk1 1: EFI EFI 209.7 MB disk1s1 2: Apple_APFS Container disk2 127.8 GB disk1s2 /dev/disk2 (synthesized): #: TYPE NAME SIZE IDENTIFIER 0: APFS Container Scheme - +127.8 GB disk2 Physical Store disk1s2 1: APFS Volume w32u SSD - Data 11.0 GB disk2s1 2: APFS Volume Preboot 24.5 MB disk2s2 3: APFS Volume Recovery 708.8 MB disk2s3 4: APFS Volume VM 8.6 GB disk2s4 5: APFS Volume w32u SSD 11.1 GB disk2s5 /dev/disk3 (internal, physical): #: TYPE NAME SIZE IDENTIFIER 0: FDisk_partition_scheme *125.1 GB disk3 1: Windows_NTFS 367.0 MB disk3s1 2: Windows_NTFS 124.7 GB disk3s2
Can I actually boot from USB with the MBR bootloader on Mac or not? I've tried any way, including rEFInd, but it results again in booting to Win10 installed on disk0 HDD.
UPD: I've noticed that my USB drive is detected as internal, that's not true. macOS Catalina Patcher's fault, I guess.