If you use an Apple computer or a computer with a Linux OS, connecting to Ragnar is very easy. All you need is a Terminal program, which Mac OS X and Linux have by default. On Mac OS X, you can find one in the “Utilities” portion of the “Applications” or just type in terminal in the Spotlight search bar. From the Terminal, you can use ssh and scp to connect and transfer files. The same commands also work in Linux. If netid is your user name on Ragnar, type

ssh netid@ragnar.econ.illinois.edu

to connect via SSH. If your user name on your computer and on Ragnar coincide, you can leave out netid@ in the preceding display.

If you want to see X windows, you should use the -Y and `C’ flags:

ssh -Y -C netid@ragnar.econ.illinois.edu

If you wish you can also set an alias for the login command and make things easier.

Getting your files into the servers

You have two options to transfer your files to the servers:

Using scp

The first one is using the scp program. For example, to copy the file filename from your home computer to Ragnar, you would use:

scp filename netid@ragnar.econ.illinois.edu:/home/netid

To copy a file (at home) from Ragnar to your home computer, the process is very similar: you use

scp netid@ragnar.econ.illinois.edu:~/exampledirectory/filename .

The period on the end is important because it tells the computer to put filename in the working directory that you are currently in at home. It can also be a path on your computer.

Using FileZilla

FileZilla is a free software that allows you to transfer files between your computer and Ragnar. It has a graphical interface and allows to transfer files using simple drag-and-drop procedures.

RSA Keys

If you work frequently with Ragnar, entering your password at each login can be avoided with the help of an RSA key. The idea is to generate two key files, a private key for your computer and a public key for Ragnar; these files are then compared automatically when you use SSH. Moreover, SSH keys provide a more secure way of logging into a virtual private server with SSH than using a password alone.

In the Mac OS X Terminal, type:

ssh-keygen

You will be asked to provide a location to generate your RSA keys. The default is

/Users/username/.ssh/id_rsa

where username is the user name on your computer. Next, you will be prompted to enter a pass phrase; this is neither your password for your computer, nor your password for Ragnar, but a third password generated by you. It should have 10 to 30 characters. Mac OS X will then generate your RSA key. In particular, your public key will be in the file

/Users/username/.ssh/id_rsa.pub

Now SSH into Ragnar and make a directory called .ssh in your home directory with

mkdir .ssh

Copy your public key file into this folder and rename it to authorized_keys on Ragnar. To copy and rename in one step, simply log out of Ragnar and enter

scp /Users/username/.ssh/id_rsa.pub <netid>@ragnar.econ.illinois.edu:.ssh/authorized_keys

in the Terminal of your Mac, where the displayed command is meant as a single line separated by a space. Log into Ragnar again and change the file permission of the public key to “read/write by owner only” with the command

chmod 600 /home/netid/.ssh/authorized_keys

The first time you SSH into Ragnar after these changes, you will be asked for the pass phrase for your RSA key. All subsequent logins will be automatic. The same steps also work with Linux, but the directory paths on your computer will most likely differ.