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

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".

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.