parted /dev/sda3
GNU Parted 2.3
Using /dev/sda3
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) mklabel gpt
Warning: The existing disk label on /dev/sda3 will be destroyed and all data on this disk will be lost.
Do you want to continue?
Yes/No? Y
Error: Partition(s) 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 on /dev/sda3 have been written, but we have
been unable to inform the kernel of the change, probably because it/they are in use.  As a result, the
old partition(s) will remain in use.  You should reboot now before making further changes.
Ignore/Cancel? I
(parted)