chromebook: in crosh, /bin and /usr/bin appear empty (cmd not found)

Using a chromebook laptop my niece got for me. I have much experience using the unix shell and prefer that to the windows interface. However, when I start up crosh, even basic commands like cd or ls provoke a "command not found" message. How can I get the shell interface to work? Would enabling developer mode do it? Thank you very much for any help you can offer.