@Sebastian-Nilsson Maybe, but be careful with the PL2303 USB TTL-adapter boards or cables - the one I have (came with a Raspberry Pi- Adafruit) measures 5 volts on the Vcc line and 4.7V on the data lines and there is no jumper option for 3v3. The Omegas are rated at 3.3 ~ 3.6V. I powered an Omega2 for perhaps an hour with that PL2303 and the Omega's RF shield got really hot, then I measured the voltage on the PL2303's lines and decided not to do that again! If you care about the longevity of your Omega powering it with 5V is not a good choice.
A CP210X adapter like WereCatf recommended is the USB TTL adapter to get, they always work and have 3V3 lines.
I too have been trying the pivot-overlay approach to expand my root fiilesystem so that I may add new development tools.
I am able to 'see', mount, and touch my ext4 formatted USB drive, but I am not able to edit my /etc/config/fstab file, since the partition is reported as 'read-only'. What am I missing? How can I get around this?
@Rudy-Trujillo @Kit-Bishop is right. I didn't see this before, but the first picture you showed might be wrong:
It says it has mounted /dev/sda as /overlay, whereas it should be one of the partitions under that drive, i.e. /dev/sda1.
You should try to use a partitioning software such as fdisk or gparted to first create a new partition on your USB drive, and then issuing mkfs.ext4 on the newly created partition. That should be able to solve your problem.
Please let me know if you have any other questions.