Missing disk half space on Ubuntu 18.04.5 LTS VPS
Solution 1:
I guess the server originally had 120 GB disk space, and the original parittioning was made according to that. After expanding the VPS disk size to 240 GB, the partitioning was not updated, so the added disk space is not in use.
To fix this, one needs to expand /dev/sda2 partition, then expand the physical volume, volume group and logical volumes. Finally the filesystem needs to be resized.