rosparam dump permission denied [closed]

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I am up to the Understanding ROS Services and Parameters in the Tutorials Wiki (cannot provide link because "Karma" is insufficient). At the end of the particular lesson, we are shown how to write all of the parameters to the file params.yaml using the terminal command $ rosparam dump params.yaml

However, I am told after executing that permission is denied.

The following is exact output I receive in the terminal

username@location:/opt/ros/hydro$ rosparam dump params.yaml
Traceback (most recent call last):
  File "/opt/ros/hydro/bin/rosparam", line 35, in <module>
    rosparam.yamlmain()
  File "/opt/ros/hydro/lib/python2.7/dist-packages/rosparam/__init__.py", line 610, in yamlmain
    _rosparam_cmd_get_dump(command, argv)
  File "/opt/ros/hydro/lib/python2.7/dist-packages/rosparam/__init__.py", line 435, in _rosparam_cmd_get_dump
    dump_params(arg, script_resolve_name(NAME, ns), verbose=options.verbose)
  File "/opt/ros/hydro/lib/python2.7/dist-packages/rosparam/__init__.py", line 293, in dump_params
    f = open(filename, 'w')
IOError: [Errno 13] Permission denied: 'params.yaml'

Running Ubuntu 12.10, with ROS Hydro.