On 02/20/17, Flavio Bessa said the following...
 
 FB> 
 FB>         "Adding group 'bbs', user 'mbse' Linux useradd: group 'admin'
 FB> does not exist"

I have no 'admin' group either and the SETUP.sh script worked perfectly for
me every time I rebuild or reinstall it.. 

You _MUST_ run the SETUP.sh script as root (do not use sudo)

sudo su -

sh SETUP.sh

If that doesn't work for you then you are one of the unfortunate. I have
never seen that issue and I have successfully built MBSE on 5 different
distros

--- Mystic BBS v1.12 A31 (Raspberry Pi)
 * Origin: internal dimension ÷ idbbs.dlinkddns.com ÷ port 59 (1:229/275)