After you increase drive's size through Virtual Media Manager, boot into Ubuntu (or connect via SSH) and run:
Verify that disk's size is not updated (also find your device path):
df -h
device path should be like /dev/sdaX
, then run:
sudo growpart /dev/sda X
sudo resize2fs /dev/sdaX
after growpart
it may ask you to fix disk's size entries, type "Fix".
You're ready! Verify that everything is now okay with df -h
(reboot may needed)
Source: https://unix.stackexchange.com/questions/564980/ubuntu-18-04-extend-disk