$  update-alternatives --config x-www-browser
There are 2 choices for the alternative x-www-browser (providing /usr/bin/x-www-browser).

  Selection    Path                    Priority   Status
------------------------------------------------------------
* 0            /usr/bin/google-chrome   200       auto mode
  1            /usr/bin/google-chrome   200       manual mode
  2            /usr/bin/iceweasel       70        manual mode

Press enter to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/bin/iceweasel to provide /usr/bin/x-www-browser (x-www-browser) in manual mode.
update-alternatives: error: unable to make /etc/alternatives/x-www-browser.dpkg-tmp a symlink to /usr/bin/iceweasel: Permission denied