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  $Id: index.rst 87 2007-10-11 22:46:18Z selfpace $

====================
CS 9E - Assignment 2
====================
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Remote Process Execution and Version Control
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  :Last Updated: $Date: 2007-10-11 15:46:18 -0700 (Thu, 11 Oct 2007) $

Background
==========

Overview
--------

This assignment will give you an introduction to networking, SSH,
remote process execution, and version control.

Reading
-------
Das: Ch. 13.12, 14.1-14.9

Version Control with Subversion: http://svnbook.red-bean.com/ - Ch. 1 and 2

`/share/b/pub/ssh.help`_

.. _`/share/b/pub/ssh.help`: http://inst.eecs.berkeley.edu/cgi-bin/pub.cgi?file=ssh.help

Assignment
==========

For the purpose of this assignment contact the SPC about getting a
second cs9e account.

Part 1 - Create SSH Key
-----------------------

Create a single passphrase protected ssh key for both accounts, and
setup your accounts to allow logins based on this key. 

Part 2 - SSH Agent
------------------

You can use ssh-agent to store your keys after they have been
decrypted with your passphrase.  This way, you can enter your
passphrase once (when you execute ssh-add) rather than every time you
make a connection with ssh.  Set up ssh-agent, add your key to the
agent, and connect to your other account using without needing to
enter a passphrase or password.

We want you to understand how the commands "ssh-agent", "ssh-add" and
"ssh" work together. Be ready to interpret to the tutor what the
printed output of ssh-agent means what the "eval" command does with
it. Demonstrate, using commands you learnt previously, that ssh-agent
is a "daemon", i.e. a command which automatically continues running in
the background once executed. Note that you need to manually kill this
daemon if you want to revert your system to pre-Part-2
state. Demonstrate that the evaluation of the printed output of
"ssh-agent" is crucial for allowing "ssh-add" and "ssh" to communicate
with the running "ssh-agent". For example, consider setting certain
environment variables to the empty string.  The "environment variable"
section of the ssh-add and ssh man pages could be helpful.

Save this session to a transcript which you will show your tutor for a
checkoff. (Note/Clarification: You will need to enter your passphrase
when you add your key to the agent, but you don't enter the passphrase
when connecting to the other account.)

Part 3 - Remote Process Execution
---------------------------------

Using a bash for loop, ssh and other common unix commands, create an
alias (Das: 9.4) that lists all users logged on to any of the
following servers: nova, quasar, and pulsar. Make sure the for loop is
written as a single line, otherwise you can't define an alias. You
should not need to enter a password (i.e. finish part 2 first), and
*your list should be sorted with no repeated entries*.  For checkoff,
bring in a transcript which shows the alias definition and usage.

Part 4 - Version Control
----------------------------------

To do this assignment, first you must create a repository.  To create a
repository, type::

    svnadmin create /path/to/repository

You should not directly edit any of the files in the repository folder.

Next, you will need to "check out" a copy of the repository in a new folder::

    svn checkout file:///full/path/to/repository newfolder

Use 'script' to record the following commands and their output so that you can show them to a tutor.

1)  Create a new empty file, test.txt, and add it to the repository.

2)  Add some text to the file, and commit the change to the repository.

3)  Check out a second copy of the repository in a second new folder.  Using these two copies of the repository, create a conflict in test.txt, and then resolve the conflict.

4)  Create another file, commit it to the repository, and then delete it from the repository.  Do not use "rm".

Assignment Checklist
====================

Part 1
------ 

* Student can demonstrate logging in to both accounts using their ssh key (not password).

Part 2
------

* Student's transcript shows correct usage and an understanding of
  ssh-agent and ssh-add and how they work together with ssh to allow
  passwordless logins.

Part 3
------

* Student's transcript shows correct alias definition and usage.
* There should not be any repeated entries.  E.g., if Alice is on both nova and quasar, her name should only appear once.

Part 4
------

* Student's transcript shows correct usage of Subversion.