external hd recognition mount unmount
1. have a 40 GB space challenged PC added 160 GB external
2. Sometimes I can boot and at these instances both drives are visible on BIOS at advanced.
3. When not able to boot with error grub loading error 21 I go to BIOS and External not visible. Unplug physically, re-plug BIOS advance sees both click f9 for load default, boot and back in.
Solutions please and thank you