I have an Acer C7 chromebook. I've installed chrubuntu using [this technique here.](http://www.youtube.com/watch?v=4qpjTzav3kw) No thumb drive, no SD card, just the hard drive. Initially, I could switch back to chrome OS using 

sudo cgpt add -i 6 -P 0 -S 1 /dev/aps

with a similar command in Chrome OS (dev mode) to get back (map 1:5 in the above command).

The first 2-3 times worked, then I spent like 3 days only using Chrubuntu & installing some python libs. Now it gives the following error when I try the shell command above from Chrubuntu:

ERROR: cgpt add: Can't open /dev/aps: No such file or directory

Any advice out there? I'm in over my head. I'd rather not restore full Chrome OS & go from there; it took a long time & I'm not sure I won't land in the same hole, again.

Background (if relevant): I gave Chrubuntu 200 gigs, and chrome OS the rest. Initially, I had no desire to go back to chrome OS. I can browse the web and, more importantly, write code with vim locally. Installing python/numpy/scipy/matplotlib all went well. However, when web browsing, frequently the system slows to a crawl, which is annoying; chrome OS was better. Now I want to go back & forth, hacking in Chrubuntu and browsing in Chrome OS. But I can't. Hence the question.