title: MongoDB password under Ubuntu
body: <p>After installing MongoDB at Ubuntu14.04, a mongodb deamon starts by user "mongodb" at group "mongodb". When modifying the /etc/mongodb.cfg, I need to restart mongod deamon.</p>
  
  <p>But how may i find the password for this user? I tried to modify the password by using "sudo passwd mongodb" and "su mongodb", but the current user is always ubuntu and there is no "authentication failure" exception.</p>