How to repair or back up external hard drive when disk utility can't repair it? I have an external hard-disk with a single Mac OS Extended partition. This disk stopped working a couple of days ago. I tried to repair the external hard drive with disk utility but no luck. The error message is the following:

Error: Disk Utility can’t repair this disk. Back up as many of your files as
possible, reformat the disk, and restore your backed-up files.


The hard drive doesn't appear on the side bar of Finder or on the desktop.
On disk utility the hard drive name appears to be on "gray" text than "black" text.

How do I repair it on the terminal?
Or how can I back up the external hard drive if I can't even access it normally?

diskutil list: 0: FDisk_partition_scheme *500.1 GB disk2 1: DOS_FAT_32 500.1 GB disk2s1 (That's one disk btw, and I don't know why it's on fat32, I last formatted it on MAC OS Extended Journaled)

Thank you
You could try to "mount" it via Terminal.

First, make a mount point:

sudo mkdir /Volumes/EXT_HD


Now mount (your device numbers may be different, e.g. /dev/disk2s1 — you can determine what it is as it will the the highest number when you issue the command ‘ls /dev/disk*’):

sudo mount -t msdos /dev/disk3s1 /Volumes/EXT_HD/


It might eventually show up in Devices in Finder.