The commands must be typed as root (FYI, # is the prompt for root), but be very careful, as under root, you can do everything, including render your tablet unusable. To get root, see the FAQ (the command "sudo gainroot" or "ssh -l root localhost" can be typed in the X Terminal).

Some more details...

If you have a N810, first reformat your internal memory card if it is incorrect. (Are all N810 affected by the bug?) There should probably be something about that in the FAQ.

The mkdir command creates the directory (with the -p option, every needed intermediate subdirectory is automatically created). You can choose another directory name, but the goal is to have it on the 2-GB card (so, it must start with /media/mmc2 or something else if you have added partitions). The mv command moves the current data (/var/cache/apt/archives directory and its contents) into the new location. BTW, these data are not important; so, you can just create the archives directory manually and the archives/partial directory. The ln command creates a symbolic link from the old location to the new location; alternatively, you can change the location in some config file in /etc/apt/apt.conf.d (but I haven't tried).

Another solution: the "apt-get clean" command (still typed as root) allows you to clean up everything in the apt archives directory; you can type it from time to time, when the memory gets full.

I don't know how to do that, but perhaps someone will write a GUI-based utility that would allow the user to choose the location of the apt archives directory and/or clean up this directory. This would be nice.