$ sudo net-snmp-config --create-snmpv3-user -ro -X DES -A MD5 -a "<PASSWORD>" -x "<PASSWORD>" <USERNAME>
adding the following line to /var/lib/snmp/snmpd.conf:
   createUser <USERNAME> MD5 "<PASSWORD>" DES <PASSWORD>
adding the following line to /usr/share/snmp/snmpd.conf:
   rouser <USERNAME>