Recovering a password in Debian Linux: in the grub boot screen where it is asking for a kernel to boot, press 'e' to edit. Append 'init=/bin/bash' to the kernel or linux option line. 'b' or F10 to boot. A root prompt should then ultimately appear. At the prompt, 'mount -o remount,rw /'. This remounts in read/write mode. Run 'passwd' to set the root password, or edit /etc/shadow and delete the root password field (not the line, just the field). Reboot.