Hi quixote,
running grub-install /dev/sda still gets me the same errors about "no space left on device." (I checked: it's 200MB, and has 98% free space.)
Do you have a separate /boot partition, and if so, how much free space does that have?
Is /dev/sda really 200MB or 200GB? Because 2% of 200MB would be a really small Debian install :-)
Cheers! Daniel
