Thank you very much for this.

When I run the sudo fdisk command on my partition I get an error:

The device presents a logical sector size that is smaller than
the physical sector size. Aligning to a physical sector (or optimal
I/O) size boundary is recommended, or performance may be impacted.

When I run:

ubuntu@ubuntu:/$ sudo fdisk -l

WARNING: GPT (GUID Partition Table) detected on ‘/dev/sda’! The util fdisk doesn’t support GPT. Use GNU Parted.

Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x58deec22

Device Boot Start End Blocks Id System
/dev/sda1 1 976773167 488386583+ ee GPT
Partition 1 does not start on physical sector boundary.

My Ubuntu OS was working fine after install but I shut down my computer and now can’t boot back into it!