I'm developing my own OS, but I'm having some problems with Qemu, because I need to change the floppy image from
os.img while the emulation is running, but how can I do this?
You can open qemu's console by pressing Ctrl-Alt-2 then type:
(qemu) change floppy0 os.img
Ctrl-Alt-1 to switch back to the VM's display.
If you start qemu from a terminal, an easier way of doing this is to run qemu with the
-monitor stdio option, which will give the same qemu console in the terminal window.