VM (virtual machines).

About VirtualBox.

http://www.virtualbox.org/wiki/Guest_OSes

Guest OSes support status for VirtualBox.

Copy and resize VirtualBox disk.

I have clear copies of several OSes for VirtualBox. When I need new one I copy and resize them to get desired size.

To copy I make a copy:

$ vboxmanage clonehd /path/to/Hurd.vdi /path/to/Hurd-new.vdi

determine size:

$ vboxmanage showhdinfo /path/to/Hurd-new.vdi

UUID:                 63b87983-3130-4db3-cd8c-6d693dcfd92b
Accessible:           yes
Logical size:         2996 MBytes
Current size on disk: 1660 MBytes
Type:                 normal (base)
Storage format:       VDI
Format variant:       dynamic default
In use by VMs:        Hurd (UUID: f7591848-2c60-4c7c-3886-b66bdb35e425)
Location:             /path/to/Hurd-new.vdi

and then apply new size (in MiB):

$ vboxmanage modifyhd --resize 35000 /path/to/Hurd-new.vdi

Next I mount parted-magic and boot to it and use gparted to extend existing fs to free space.