# Find the label of the drive you are trying to add. Tutorial uses sdb as the new drive.
sudo fdisk -l
# Partition the hard drive as Linux LVM:
sudo fdisk /dev/sdb
# Initialize partition for use by LVM (after you partition it places a number 1 in front of the drive label):
sudo pvcreate /dev/sdb1
# Display attributes of volume groups to find your group name (mine is ubuntu-server):
sudo vgdisplay
# Add the new physical volume to existing volume group:
sudo vgextend ubuntu-server /dev/sdb1
# Now extend the logical volume root to include the new physical volume(the 128G represents 128GB, this number represents the entire sive of the logical volume:
sudo lvextend -L128G /dev/ubuntu-server/root
# Lastly, resize the file system to include the new free space(this may prompt for you to check the file system first, this process will be the longest:
sudo resize2fs /dev/ubuntu-server/root