Warning: /dev/sda contains GPT signatures, indicating that it has a GPT table.
However, it does not have a valid fake msdos partition table, as it should.
Perhaps it was corrupted -- possibly by a program that doesn't understand GPT
partition tables.  Or perhaps you deleted the GPT table, and are now using an
msdos partition table.  Is this a GPT partition table?
Yes/No? ^C                                                                
Model: ATA TOSHIBA THNSNH25 (scsi)
Disk /dev/sda: 256GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt