Initial Setup

Help!
Set Up SSH
Changing Your Shell
Get the GPI Configuration
Get a Lern2Unix Account

Help!

If at any point you get stuck during this initial setup or throughout the semester, please don’t hesitate to email the course staff at 15-131-staff at cs dot cmu dot edu.

Set Up SSH

SSH is a program that lets you log in to a server and run commands on it. At CMU, you’ll use SSH extensively in most of your CS classes. SSH is also a very important tool for working in industry and knowing how to use it will be essential throughout your career. (Even in academia, SSH is a very important tool.)

Throughout the rest of the semester we’ll teach you about how to use it and why you want to, but for now we’ll just focus on getting it set up so that you can start using it right away.

The exact instructions on how to set up SSH vary based on what operating system you’re using, so choose the relevant section and proceed from there.

Congratulations! Your OS has a built-in terminal (Terminal.app), so you don’t need to download anything. You might consider looking at one of the other terminals for OS X like iTerm2 if you want cooler features like better color support, easier theming, vertical splits, advanced tmux integration, and more.

Sshing is simple; run the following command, replacing ANDREWID with your Andrew ID:

ssh ANDREWID@unix.andrew.cmu.edu

When you enter this, you will be prompted for a password–it’s the same password you use to log onto WebISO.

To facilitate quick sshing, you should edit the ssh config file. Use the following command to do that (you don’t need to understand this command yet–we’ll cover it later in the semester). Copy and paste the command into your terminal and hit enter.

mkdir -p ~/.ssh; touch ~/.ssh/config; nano ~/.ssh/config

Add the following (replacing ANDREWID with your Andrew ID) to this file, save the file, and exit nano. (Some notes: The ^ character is used to represent the “control” key, so ^O means “hold control and press the O key”, and nano uses “WriteOut” to mean “save”. Nano will ask you to confirm the filename you want to save. Just hit enter to confirm it.)

Host andrew
Hostname unix.andrew.cmu.edu
User ANDREWID
GSSAPIAuthentication yes
GSSAPIDelegateCredentials yes

Normally, without the above incantation, you would need to type ssh ANDREWID@unix.andrew.cmu.edu to ssh, but now you can just type ssh andrew and the rest will be auto-detected. If you prefer a different name than andrew, you can change that line (Host andrew) in the ssh config file.

First, you should choose a terminal. Your distro almost certainly has one already, but if you don’t the default one you can download another. Some popular terminals are

Terminator
Konsole
Gnome Terminal
xterm
xrvt-unicode

Once you’ve done that, follow the instructions in the Mac section.

We recommend that you use MobaXterm for SSH. For detailed installation and setup instructions, see this blog post.

If you’re already somewhat familiar with Linux, however, we strongly recommend that you follow the Linux initial setup instructions.

A Note About Terminals

I’m using the word “terminal” here for consistency with the way people use the word commonly. To be technically correct, I should call it a “terminal emulator,” but this phrasing could lead to confusion so I’m using the slightly less correct phrasing instead.

Changing Your Shell

A shell is a program that lets you enter in text commands to a computer and get output from those commands. Shells are essential for using SSH and very useful for programming. We’ll be doing all of our work in this class within a shell, so it’s important that we use the right one!

The default shell on Andrew Linux systems, csh, is lacking in many ways. For that reason, we’ll be switching you over to a shell called bash. (If you have strong preferences about your shell, you’re welcome to use another shell as long as it’s not csh.)

In order to switch your shell over, follow these instructions:

SSH into andrew using the setup you did above.
Run the command chsh at the prompt (type it and hit enter).
You’ll be asked to enter a new shell. (When doing this, be very careful; if you enter something that isn’t a shell, you will not be able to use your account until the problem is fixed, which is not easy to do!) Type in /bin/bash and hit enter.
If you log out (disconnect) and connect again, your new shell should be bash. (It says it will take a long time, but it’s generally nearly instantaneous. If it’s taking longer than 30 minutes, you might want to send us an email.)

When entering your new shell for step 3, mistyping the shell will cause you to be locked out until the problem is fixed, which takes at least a day to do.

You can disconnect by either typing “logout” and hitting enter or by using the keyboard shortcut ^D (control-D). ^D is a very common keyboard shortcut that very often will exit you out of programs like shells, command prompts, and REPLs.

Get the GPI Configuration

The default settings for bash (the shell you switched to) and other programs you’re likely to use during the semester are rather minimal, so we’ve written some configuration files that will give you nicer defaults. Of course, if you want to change these settings to better fit your preferences you can do so.

SSH in to andrew.

First, we’ll get a few basic files. Copy the following commands into your terminal, hitting enter after each one.

curl https://raw.githubusercontent.com/cmugpi/dotfiles/master/bash_login > ~/.bash_login
curl https://raw.githubusercontent.com/cmugpi/dotfiles/master/bashrc > ~/.bashrc
curl https://raw.githubusercontent.com/cmugpi/dotfiles/master/bashrc_gpi > ~/.bashrc_gpi

curl https://raw.githubusercontent.com/cmugpi/dotfiles/master/vimrc > ~/.vimrc
git clone https://github.com/gmarik/Vundle.vim ~/.vim/bundle/Vundle.vim
vim +PluginInstall +qall

Side note: these will overwrite any existing files you might have. If you have your own bashrc or vimrc, read the Advanced Usage instructions.

Then, disconnect from Andrew (remember, ^D) and log in again. When you’ve logged in, type echo $GPI_PATH and hit enter. If you see a file path, then everything went correctly! (If you see nothing, something went wrong. Try logging out and back in, and if that doesn’t fix it, make a post on Piazza or email us.)

Get a Lern2Unix Account

We’ll be using the lern2unix website as a backend to submit and download problems, so you’ll need a lern2unix account which you should sign up for before our first lecture.

IMPORTANT: You need to use your AndrewID for your username and your andrew.cmu.edu email address for your email.