I actually solved this this morning.
Found this site : http://www.marktomlinson.com/2011/08/sy ... -password/
and to write it here in case site goes offline or changes :
The next thing I wanted to do, obviously, was to change this default password. Normally on 'nix systems you would use the *passwd* command, but the BusyBox shell doesn't have one. A little poking around reveal the Synology way to set the password:
`synouser --setpw root `
Where `` is your preferred password: `FredQK2` for example. By the way when you log in as root for the first time the shell tries to change to your home directory and you may notice the following message:
*Could not chdir to home directory /var/services/homes/root: No such file or directory*
The problem is that root doesn't have one set by default. You will need to create one – if the message bothers you. Just type the following command at the prompt:
Otherwise it isn't important as you'll be logged in only into the / (root) directory."
Hope it helps