Okay, you can't use sudo in this way on the N900.

By default, your x-terminal session is run by the "user" user account. If you want to sudo any commands, the user account would have to have an entry in the /etc/sudoers file.

And if you did, then you would still be prompted for a password when trying to execute the sudo command, but this would be expecting the user account's login password.

The user account has no password on it by default, so you have nothing to input, and even if you did it would still report that the user account is not in the sudoers file.

To get around this, as has been stated before, you would need to install the rootsh application and then issue the sudo gainroot command in x-terminal prior to running priviledged commands.