I recently installed the macOS Mojave developer beta on my MacBook Pro. Everything worked fine and I could start both macOS and Windows.
Today, when updating to the beta 2, however, the installation got stuck at 16 minutes remaining for over an hour at which point I force restarted the computer.
macOS still boots fine. Also Windows still appears as an option when I hold down the ⌥ (Option) key on boot. However, when I click on it macOS starts instead.
In Disk Utility a disk is not mounted and I cannot repair it. There is only one 512GB SSD that macOS and Windows share.
diskutil list outputs the following:
/dev/disk0 (internal):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme 500.3 GB disk0
1: EFI EFI 314.6 MB disk0s1
2: Apple_APFS Container disk1 120.0 GB disk0s2
3: Microsoft Basic Data 379.5 GB disk0s3
4: Windows Recovery 491.8 MB disk0s4
/dev/disk1 (synthesized):
#: TYPE NAME SIZE IDENTIFIER
0: APFS Container Scheme - +120.0 GB disk1
Physical Store disk0s2
1: APFS Volume Macintosh HD 75.9 GB disk1s1
2: APFS Volume Preboot 23.3 MB disk1s2
3: APFS Volume Recovery 510.5 MB disk1s3
4: APFS Volume VM 1.1 GB disk1s4
How to get Windows 10 to boot again?
Best Answer
A workaround I have discovered is to go to System Preferences -> Startup Disk, and select the OS that you cannot now access from the boot screen as your default startup OS (in my case Boot Camp Windows 10). Then at the boot screen you can access Mojave as normal when you want to. It is not really a fix but an easy workaround until the fix comes out. It worked for me at least.