How to mount USB Drive in Single User Mode in Mac OS X

Question

I have faced a problem where my Mac is not booting up and throwing messages like this continuously.

process[182] crashed: opendirectoryd. Too many corpses being created.

I tried repairing the Hard Disk and re-installing OS, but that didn't fixed the issue. So before i erase the disk and re-install again, i have to backup my files. So i boot-ed up in Single user mode, but i wasn't able to mount the pen drive, as High Sierra prevents loading unsigned kernel extensions, in this instance msdos kext for mounting my FAT formatted pen drive.

So i eventually fixed it with the help of online forums and i m putting it together so that it can be useful to others as well.

Answer 1

1. In order to run un-signed Kernel extensions in Mac, you need to disable Apple Signature check for loading Kernel extensions.

   Reboot Mac in Recovery mode(Command + R), then select the menu item "Utilities / Terminal", then run the command

   csrutil disable
   

   Reboot in Single User mode (Command + S)

2. Enter the following commands,

   fsck –fy
   
   mount –uw /
   

3. Create a directory to mount USB Drive

   mkdir /Volumes/usbmnt
   

4. Before plugging in the USB Drive, get the list of "disk" devices available by running the command

   ls -l /dev/disk*
   

5. Plug in the USB disk

6. Identify the new device entry for the USB disk by again running the command

   ls -l /dev/disk*
   

   Usually the disk will be mounted like '/dev/disk2s1'

7. Identify the file system of the USB disk

   fstyp /dev/disk2s1
   

8. Based on the file system format, mount the USB Drive; my USB format was "FAT", so I used msdos:

   mount_msdos /dev/disk2s1 /Volumes/usbmnt
   

That's it; now the USB drive is mounted. Use the contents of the drive at the path filesystem "/Volumes/usbmnt".

Answer 2

Another way to accomplish this is to boot to recovery instead of single user mode. Once in recovery, the system mounts USB drives to /Volumes just like in the full OS except you don't even need your full OS to be bootable.

1. Hold Command R when starting
2. Select Terminal from the Utilities Menu
3. Plug in the USB drive and you are done