How do I expand the root's volume size?

Solution 1:

As you can see, there's about 9.58 GiB free in your volume group, so that's how much space you can add to the logical volume.

First, you can use lvextend to extend the size of the logical volume, to fill up the remaining space:

sudo lvextend --extents +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv

Now, you can resize the filesystem in that logical volume.

sudo resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv

Finally, you can see the end result:

sudo df -h /