How to increase VirtualBox virtual drive actual size?

I have selected "dynamically allocated" mode upon creating virtual drive. I was thinking it will grow automatically up to maximum size. But it constantly has "actual size" of 4Gb and does not growing to 8Gb which is virtual size. Guest OS says it has no more space on drive on /dev/sda1.

Is it possible to kick it somehow?

Thanks

If you want to add space to the guest, there's 2 places it needs done: First in the virtualization host itself (Virtualbox, in your case), then again inside the guest.

If you originally created the virtual drive as 4 GB, then later resized it to 8 GB, you'll need to do some work in the guest OS to have it makes use of the extra space. Right now it's as if you took a 4 GB partition and put it onto an 8 GB drive -- the partitions haven't changed, so the rest of the space is unallocated as far as the guest is concerned. You can either add a 2nd partition in the guest or use some utility to resize the partitions in the guest.