Fdisk

Resizing existing disk space on root fs without using gparted.

- First, increase vmdisk space in your vm host gui/cli interface.

- Second, in your OS with root access
sudo fdisk /dev/sda
Command (m for help): p
Command (m for help): d
Command (m for help): d
Command (m for help): n
 - e (extended (if dos)
Command (m for help): n
Command (m for help): t (8e)
Command (m for help): w
(if not unmounted before you might need to reboot or lazy unmount umount -l /opt

lsblk

sudo pvresize /dev/sda5 (lvm disk you increased in fdisk)
sudo lvextend -L100G /dev/vg00/opt  (extend whatever patition size you want