After webui crashed due to full hard drive, I can't get it to work again

following this discussion:

root@debian:/usr/games/minecraft# node ‘password tester.js’
testing etc_shadow
expected value: mc
returned value: false

testing posix
expected value: mc
returned value: true

testing pam
expected value: mc
returned value: true

So whatever etc_shadow is that is failing is (a) problem. But the other 2 auth methods are passing which should allow me to login to webui