What is SSH?

We are currently in the process of migrating our HOWTO articles to a new CCIS Knowledgebase. The content of this page has been moved to the following KB article:

KB0012109: What is SSH?

Click here to expand the deprecated HOWTO page

This page is intended for those who are not familiar with ssh.

What is this “ssh” thing?

At it’s most basic, ssh is a method to connect securely from a local computer to a command-line session on a remote computer. It is the method by which our CCIS Linux machines are available for remote use. Connecting to a CCIS machine via ssh is the first step in signing up for a CCIS account.

ssh is capable of more than we outline above (it’s a pretty hand tool), but that’s it in a nutshell.

So how do I use ssh?

In order to connect to a remote server via ssh, you’ll need what’s called an “ssh client.” Just as your web browser (eg: Chrome, Firefox, Internet Explorer, Safari, etc…) is your means of browsing the web, an ssh client is your means of connecting to a remote ssh server like the ones we run here at CCIS.

But first, a note on security: If you follow the directions below, and start receiving errors of the form “server unexpectedly closed network connection,” you might have fallen afoul of one of our security systems. If this happens: Don’t worry! Just visit our page about automatic blocking of repeated failed ssh login attempts, and follow the directions you find there!

That having been said, your options for an ssh client depend on your Operating System.

If you are using:

Microsoft Windows

We recommend the excellent PuTTY, by Simon Tatham. PuTTY is free to download and use without charge. (It’s also Free/Open Source software – if you don’t know what that means, don’t worry!)

To download and use PuTTY, please refer to the link above. (You just want to download PuTTY (ie: putty.exe) for now. Later, feel free to explore any of PuTTY’s add-on programs, such as PSCP, PSFTP, etc. Note that PuTTYtel (puttytel.exe) will not work to connect to CCIS Linux systems, as it only provides support for the older telnet protocol, a totally different thing from ssh.)

Once you’ve got PuTTY up and running, simply:

  1. enter login.ccs.neu.edu in the “Host Name (or IP address)” field
  2. click the “Open” button
  3. A “PuTTY Security Alert” dialog should appear stating “The server’s host key is not cached in the registry. You have no guarantee that the server is the computer you think it is…” (and so on). If you are the kind of person who really cares about security, you can learn how to verify a server’s identity remotely. For now, just click “Yes” to add login.ccs.neu.edu‘s “ssh host key” to the list of ssh servers PuTTY knows about.
  4. A window should appear containing the prompt “login as: ”. Here you should enter the login name you are using: “account” if you are doing the CCIS Account signup process, or your CCIS account if you are connecting to one of our ssh servers after your account has been set up.
  5. In the same window, you should then receive the prompt “[Account you provided]@login.ccs.neu.edu's password: ”. Here you should enter the appropriate password: “account” if you are doing the CCIS Account signup process, or your CCIS password if you are connecting to one of our ssh servers after your account has been set up.
    Note: PuTTY does not display any characters on the screen when you type in your password, not even “*”. This is an intentional security measure to keep someone who can see your screen from knowing how long your password is. A side effect, however, is that sometimes people think PuTTY isn’t accepting their input. It is! Just type in your password (ignore the lack of response on the screen), and hit Enter!
  6. That’s it! You should be in! When you’re done, end your session by typing “exit” or “logout.” (Note: That step doesn’t apply to using ssh for the CCIS Account signup process.)

Mac OS X, Linux, BSD, and other UNIX variants

Most UNIX variants (don’t worry if you don’t know what that means), including Apple’s Mac OS X, most Linux distributions, Free/Net/Open/Dragonfly/etc BSDs, commercial UNIXes like Solaris/AIX/etc, and so on already include a fully functional ssh client called, appropriately enough, “ssh”!

To use this built-in ssh client:

  1. Open a Terminal. On Mac OS X, the Terminal is located in your Applications -> Utilities folder (Applications is the folder on your hard dirve that contains Safari, Mail, etc). On newer versions of OS X, you can also go the route: Launchpad -> Utilities. The location of the terminal varies on other Linux and UNIX distributions.
  2. Once your Terminal is open, type the following at the prompt: ssh [Account You're Using]@[Server to which You're Connecting], then press Enter or Return on your keyboard. eg:
    • ssh account@login.ccs.neu.edu if you are doing the CCIS Account signup process, OR
    • ssh [Your CCIS Login]@login.ccs.neu.edu if you are connecting to one of our ssh servers after your account has been set up
  3. You should receive output along the lines of “The authenticity of host 'login.ccs.neu.edu (129.10.117.100)' can't be established... Are you sure you want to continue connecting (yes/no)? ” If you are the kind of person who really cares about security, you can learn how to verify the authenticity of a server’s identity remotely. For now, just type “yes” to add login.ccs.neu.edu‘s “ssh host key” to the list of ssh servers ssh knows about.
  4. You should then receive a prompt for account@login.ccs.neu.edu's password: (or similar). Here you should enter the appropriate password: “account” if you are doing the CCIS Account signup process, or your CCIS password if you are connecting to one of our ssh servers after your account has been set up.
    Note: ssh does not display any characters on the screen when you type in your password, not even “*”. This is an intentional security measure to keep someone who can see your screen from knowing how long your password is. A side effect, however, is that sometimes people think ssh isn’t accepting their input. It is! Just type in your password (ignore the lack of response on the screen), and hit Enter/Return!
  5. That’s it! You should be in! When you’re done, end your session by typing “exit” or “logout.” (Note: That step doesn’t apply to using ssh for the CCIS Account signup process.)

What else?

That’s it! As mentioned above, ssh can do a whole heck of lot more than we mention here, including neat things like port forwarding, acting as a SOCKS proxy, tun/tap VPNs, sftp & scp for file transfer, key-based authentication, and so on, but all of those things are beyond the scope of this basic intro.

Enjoy, and happy sshing!

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