How to restore unreadable USB flash drive under Mac OS X
| 1. Open Terminal and go to /dev | |
| $ cd /dev | |
| 2. Now it’s time to find your flash drive in /dev. Typically it’s /dev/diskN where N could be 0, 1, 2, 3, etc | |
| $ diskutil list | |
| /dev/disk0 | |
| #: TYPE NAME SIZE IDENTIFIER | |
| 0: GUID_partition_scheme *121.3 GB disk0 | |
| 1: EFI 209.7 MB disk0s1 | |
| 2: Apple_HFS Macintosh HD 120.5 GB disk0s2 | |
| 3: Apple_Boot Recovery HD 650.0 MB disk0s3 | |
| /dev/disk3 | |
| #: TYPE NAME SIZE IDENTIFIER | |
| 0: GUID_partition_scheme *8.1 GB disk3 | |
| 1: EFI 209.7 MB disk3s1 | |
| 2: Microsoft Basic Data KB 7.9 GB disk3s2 | |
| OK! It’s disk number 3, i.e. /dev/disk3 Remember the name of partition (it’s KB in my case). Your flash drive is mounted as /Volumes/NAME | |
| 3. Let’s erase and reformat the disk. In 90% you will get a message that the system can’t unmount your drive. | |
| $ diskutil eraseDisk MS-DOS KB /dev/disk3 | |
| Started erase on disk3 | |
| Unmounting disk | |
| Error: -69888: Couldn't unmount disk | |
| Use the partition name from step 2. | |
| $ diskutil unmountDisk force /Volumes/KB | |
| Forced unmount of all volumes on disk3 was successful | |
| $ diskutil eraseDisk MS-DOS KB /dev/disk3 | |
| Started erase on disk3 | |
| Unmounting disk | |
| Creating the partition map | |
| Waiting for the disks to reappear | |
| Formatting disk3s2 as MS-DOS (FAT) with name KB | |
| 512 bytes per physical sector | |
| /dev/rdisk3s2: 15377032 sectors in 1922129 FAT32 clusters (4096 bytes/cluster) | |
| bps=512 spc=8 res=32 nft=2 mid=0xf8 spt=32 hds=255 hid=411648 drv=0x80 bsec=15407104 bspf=15017 rdcl=2 infs=1 bkbs=6 | |
| Mounting disk | |
| Finished erase on disk3 | |
| That’s all. Now you have a USB flash drive again. |
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