I incorrectly modified the /etc/environment file; now when I try to login the session terminates within 10 seconds. I've tried to edit the environment file through a failsafe session, but I don't have access to vi, vim, pico, etc. I keep getting the message "command not found." Anyone know how to gain access to the /etc/environment file through an editor so that I can undo my changes?

Solution:
Booting into single-user mode allowed me to edit the file.