At the login screen, when presented with only the 'guest account' do the following:
Ignore the password box and click on the 'guest user head icon' this should bring up -
'This computer will restart to a secure, Safari-only system for the Guest user'
click 'Cancel' then hold down 'control' + 'option' + 'command' and tap 'enter'
your usual login entry boxes (username and password) should show.
This technique will get you into your system without the need for Terminal tweeks.
If you wish, from here you can disable this security feature in System Preferences / Internet & Wireless / iCloud, unclick 'Find My Mac' - the 'guest account' will now not show at login, only you usual login identities.