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Emulab FAQ: Using the Testbed: Can I modify my experiment after creating it?

Emulab FAQ: Using the Testbed: Can I modify my experiment after creating it?

Yes. On the experiment view page, choose "Modify this Experiment". This will allow you to modify an experiment, either swapped-out or in, by editing its NS file. This is also know as swapmod in other sections of the Emulab documentation.

If the experiment is swapped-out, Experiment Modify will simply replace its topology with the newly specified one; this new topology will be mapped when the experiment is swapped in.

If the experiment is already swapped-in, Modify will change the topology and map in the portions which have been changed. This allows dynamic addition, subtraction, and replacement of an experiment's nodes and links. However, when modifying swapped-in experiments, there are a couple things to keep in mind:

  • Any node with the same name in the old and new topology will remain on the same physical machine, unaffected-- its disk will not be reloaded. If you want to, for example, change the hardware on a machine, you will have to call the machine something different in the new topology.
  • It is highly recommended that you leave the "Reboot nodes in experiment" box checked in the Experiment Modify form. This is especially important if changing your experiment topology (adding or removing nodes, links, and LANs). If adding/removing a delay to/from an existing link, or replacing a lost node without modifying the experiment topology, this won't be necessary.
  • The event system is not automatically restarted for your experiment, so you will not be able to modify the traffic shaping for new links. In addition, if you add program agents or traffic generators, these will not activate unless you restart the event system by hand. Unfortunately, all events will be replayed, so be careful: On, you may do the following: eventsys_control [-f] replay proj expt