Thank you very much for your detail reply.
But I would like to launch 'default' which required 4GB RAM not express.
Because express version requires 8GB and my virtual box has max 7GB.
How to launch default VM?
[cloudera@quickstart ~]$ sudo /home/cloudera/cloudera-manager --express
WARNING: It is highly recommended that you run Cloudera Express in a VM withat least 8 GB of RAM.
You can override these checks by passing in the --force option,e.g:
sudo /home/cloudera/cloudera-manager --force[cloudera@quickstart ~]$