[cs615asa] HW#3 grades

[Jan Schaumann]

Hello,

I have just sent out grades for HW#3.  If you did not receive a grade,
please let me know asap.

Here are a few things you should consider if you wish to improve your
program:

- Use EC2_RUN_INSTANCES_FLAGS in ec2-start-instance to allow the user to
  specify flags to ec2-run-instances.  (Yes, this was explicitly noted
  in the requirements, but many of you chose to ignore that part and
  hardcoded some things or required the user to do other things.)

- Don't hardcode ssh flags -- as per the instructions, you can assume
  that the user has his or her ssh configuration set up.

- use the ec2-start-instance tool you wrote in ec2-backup

- when backing up using dd(1), do not create a tar file first and then
  write that file to a file on the remote side; instead, use a simple
  pipeline

  tar cf - $DIR | ssh $instance "dd of=/dev/whatever"

- Be more resilient to failure!  Things go wrong all the time; make sure
  your program can handle the failure.  You cannot assume that a given
  mountpoint is not in use, even if in the cases you came up with it
  wasn't.  Recall that anything that can fail, will.  Make sure to check
  for errors and act accordingly.  Gracefully aborting is preferable to
  plowing ahead in the hopes that all will be well.

- Make sure you handle the case where the volume already exists and is
  or isn't attached to an instance.

- Do not rely on 'ec2-describe-tags' to identify resources; tags can
  exist and be assigned to resources that have been deleted.

- Do not hardcode anything relating to your particular setup.

- Always think about whether or not your program makes any assumptions
  or requires any knowledge about your environment.  The user must not
  need to modify the tool in order to make it work.

-Jan