Theoretically it should just work OOTB. I.e. start VM; run through inithooks (enter passwords etc), then you should be able to log in to the various services using the relevant username ('root' for most things; 'admin' for Redmine itself) and password (Linux root user password for Webmin, Webshell and SSH; MySQL root password for Adminer/MySQL; 'admin' for Redmine). The fact that you can't log in to anything suggests to me that there is something you are not doing quite right...

However, the fact that you state you are trying "su - root" makes me think that you have actually completed the inithooks but just don't realise it...

My deepest apologies. Is the error that you are having the same as what is described in this thread?

If so there is a workaround there. Also it was rebuilt a couple of days ago so you may have downloaded the broken one, just before we uploaded the fixed version...