If you’ve upgraded your iMac to macOS Sequoia on an external SSD with OpenCore Legacy Patcher (OCLP) and previously experimented with a Linux Mint dual-boot, you may have multiple EFI partitions cluttering your system. Here’s a guide to help set your external SSD as the main boot device and clean up unnecessary EFI partitions safely. Step 1: Identify EFI Partitions and Mount the Correct One Identify All EFI Partitions : Open Terminal and list all partitions: bash Copy code diskutil list Locate your external SSD and note its disk identifier (e.g., disk2s1 for the EFI partition on the external SSD). Mount the Correct EFI Partition : Mount the EFI on your external SSD (the one with macOS Sequoia installed): bash Copy code sudo diskutil mount diskXsY Replace X and Y with the disk and partition numbers of the external SSD’s EFI. Step 2: Set the External SSD as the Default Boot Device Open Startup Disk Preferences : Go to System Preferences > Startup Disk . Select the external SSD ...
Setting Your External SSD as the Primary Boot Drive on iMac (Late 2015) and Cleaning Up Extra EFI Partitions