I have 16 GB SanDisk USB-C drive and want to convert it to GPT on MB Pro 2017. I haven't found any default tools to do this on High Sierra so I downloaded gdisk. So here is what I type in the terminal:

sudo gdisk /dev/disk2s1/Volumes/BOOTABLE

and the output is:

GPT fdisk (gdisk) version 1.0.3
Problem opening /dev/disk2s1/Volumes/BOOTABLE for reading! Error is 20.

How can I convert it to GPT?

EDIT: I converted drive to GPT using sudo gdisk /dev/disk2 but the following issue appeared:

Caution! After loading partitions, the CRC doesn't check out! Warning! Main partition table CRC mismatch! Loaded backup partition table instead of main partition table!

Warning! One or more CRCs don't match. You should repair the disk!

Partition table scan: MBR: protective BSD: not present APM: not present GPT: damaged

I verified it and got the message:

Problem: The CRC for the main partition table is invalid. This table may be corrupt. Consider loading the backup partition table ('c' on the recovery & transformation menu). This report may be a false alarm if you've already corrected other problems. Identified 1 problems!

So I tried to do as advised and got this:

Recovery/transformation command (? for help): c Warning! This will probably do weird things if you've converted an MBR to GPT form and haven't yet saved the GPT! Proceed? (Y/N):

Should I load backup partition table from disk (rebuilding main) or load MBR and build fresh GPT from it?


1 Answer 1


Ok, I entered Recovery/transformation commands and selected load MBR and build fresh GPT from it. After that I chose write table to disk and exit. Operation completed successfully.

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