Only the FAT32 file system of Windows platform is what I have found working flawlessly. If not formatted on Mac, You can format it under FAT32 filesystem on windows. Also make sure the USB disk or external drive that you are going to mount in SUM on mac, is formatted on Mac. So if you have never used this command line environment or UNIX and Linux OS, make sure you type every command very carefully. Root user can make any changes and delete any files on your Mac. Warning: In SU Mode, your Mac boots in root user environment.

This post will show you simple steps to mount USB or external drive in Single User Mode on Mac. In Single User Mode(SUM) you need to first mount USB or external drive to copy data over to it. The only way your Mac can boot for sure is “Single User Mode”. But there is still a way to boot your Mac and recover data from there. You can’t boot your Mac and can’t copy the data over to an external hard drive or USB disk. In such situations, your important data is at stake. This article is specially written for those who are unable to boot their Mac in normal mode or Mac boot process stuck at grey screen with Apple logo and a loading bar.