SSH tutorial

In order to secure the University of Toronto Mathematics network we are encouraging users to start using encrypted protocols such as "ssh" and "scp" to log into our machines and transfer files between them. Older programs such as "telnet" and "ftp" transmit all information as plain, human-readable text, which represents a security risk since it is very easy for a would-be intruder to capture passwords and other sensitive information. Please read this document in its entirety before using "ssh". If you have any questions or comments regarding this web page or these programs please feel free to send an email to the Math system administrators at: requests@math.toronto.edu.

For the Windows platform we suggest downloading PuTTY, which is a free ssh client. Installing requires downloading the following files (v. 0.57):

• putty.exe
• puttytel.exe
• pscp.exe
• psftp.exe
• plink.exe
• pageant.exe
• puttygen.exe

and saving them into a directory of your choice. Below is a step-by-step guide for the installation and use of the PuTTY files mentioned above (click on the images to enlarge):

	The two executables you'll use actively are "putty" and "pscp".
	To ssh into the department, double click on the "putty" icon. This will open a window called "PuTTY Configuration" like the one shown on the left. Click the SSH radio button and write coxeter.math.toronto.edu in the Host Name (or IP address) field.
	Make sure 2 is selected from the Preferred SSH protocol version field located under Connection - SSH.
	If you would like to save your settings for future sessions go back to Session and type a name under Saved Sessions. After clicking Save the name will appear in the large box to the left of the button. You can then Load the settings again next time you start PuTTY. You can now click on Open to connect.
	If you have an X Windows server installed (such as eXceed) and would like to open windows through an encrypted tunnel select Enable X11 forwarding. This is an advanced feature, however, so please ask your systems administrator for assistance if needed.
	The first time you connect you will see the dialogue box shown here. Click Yes to continue. This message should only appear the first time you connect! Otherwise contact your systems administrator.
	You can now log into the system.
	To copy files securely you will need to use pscp. The first step is to open a "Command Prompt" window as shown to the left. In some versions of Windows this icon is called "MS-DOS" and may be located in some other location under the "start" menu.
	Here is a sample transfer. Note that you must write the full "pscp" path (alternatively you can add the location of pscp.exe to your PATH variable under Windows if you know how). The syntax is similar to that of scp as discussed below. Note that another, simpler alternative is to use WinSCP (see below).

Some people find it easier to work with a graphical interface instead of the command-line pscp command. Another possibility in this case is to use a program called WinSCP. First you need to download the following file (v. 3.7.4):

• WinSCP

Below we explain how to use it:

WinSCP
	When you download WinSCP you'll find an icon like the one shown to the left. Double-click and follow the instructions on how to install (an install wizard will appear after double-clicking). It is recommended you do this as Administrator.
	The entries here are pretty self-explanatory. Choose the appropriate host if not connecting to coxeter, otherwise just follow the example shown. Session parameters can be stored for future use using the Save button.
	Make sure 2 is selected from the Preferred SSH protocol version field located under Environment - SSH.
	The first time you connect this box will appear. Click OK. This message should only appear the first time you connect! Otherwise contact your systems administrator.
	You can now copy files back and forth between computers.

If you use a reasonably modern version of Linux or *BSD (i.e. any distribution available since 1999) it should come with openssh installed. If not the files are available at www.openssh.org. The generic use of these commands is as follows:

   ssh computername

   scp myfile.ext computername:/path/to/file/

   scp computername:/path/to/file/myfile.ext /local/path/

The table below summarizes the use of ssh and scp via various examples:

 Jane is on "coxeter" and wants to log into "janepc":

    ssh janepc

 Conversely, if Jane is on "janepc" and wants to log
 into "coxeter":

    ssh coxeter

 Suppose that Jane's account name on "janepc" is "jjane"
 but her account name on "coxeter" is simply "jane".  From
 her computer she should type:

    ssh jane@coxeter

 to log into "coxeter". Use the "-X" option to be able
 to open windows over your ssh session (so that you can
 open an xdvi session from coxeter, for example):

    ssh -X coxeter

 We assume you are logged on to YOUR personal computer
 ("~" is equivalent to your home directory "/home/yourname"):
 
    scp file1.tex coxeter:~/mylatex/       (copies file1.tex TO coxeter
                                            "mylatex" directory)
    
    scp coxeter:~/mylatex/file1.tex ~/Q1/  (copies file1.tex FROM coxeter
                                            TO local "Q1" directory)
    
    scp ~/pix/*.jpg coxeter:~/mypix/       (copies all .jpg files TO
                                            "mypix" directory on coxeter)
    
    scp coxeter:~/mylatex/'*'.tex .        (copies all .tex files FROM
                                            coxeter "mylatex" directory
                                            TO the local directory in
                                            which you currently are in
                                            [the one you get by typing
                                            "pwd"].  NOTE: the asterisk is
                                            in single quote marks here since
                                            you want it interpreted on the
                                            remote machine, coxeter)
    
 If you are ON COXETER the syntax is the same but instead of "coxeter:"
 above you would type "computername:" e.g.
 
      scp file1.tex computername:~/mylatex/

For more information you can type sshinfo and scpinfo at the coxeter prompt, or run man ssh and man scp.

For access to a linux graphical front-end which is similar to winscp you can type gftp at the command-line (or click on the icon if available).

Even though it is well-known for its elegant user interface, Mac OS X is a robust Unix-based operating system containing all the power and functionality that Unix and Linux users are accustomed to. Accessing coxeter with ssh is extremely simple in Mac OS X since openssh is built in. This section assumes that you have some familiarity with the Mac OS X user interface. If not, choose Mac Help from the Finder Help Menu to learn about Mac OS X.

The easiest way to log into coxeter is to open Terminal which is located in your Applications >> Utilities folder.

Using the Finder window to open Terminal

If you plan on using Terminal extensively to access coxeter, we recommend that you place Terminal in your Dock [screenshot]. Once you have connection to the Internet and you have a Terminal window open, you can use the normal Unix commands as described in the Unix and Linux section above to log into coxeter.

Logging into coxeter for the first time using Terminal.

If you wish to use X Windows applications on coxeter such as xdvi, emacs, or xmaple, you can run X11 instead.

X11 requires Mac OS X 10.3 Panther, 10.4 Tiger, or 10.5 Leopard. X11 is not installed by default on Panther or Tiger, but it is included in the Mac OS X Panther Install Disk 3 CD or the Mac OS X Tiger Install DVD. Once installed, X11 is also located in the Applications >> Utilities folder.

Once X11 is open, a Terminal window opens and you may use ssh -X to log into coxeter. Witness an X11 session in action with X11 applications open: Half-size screenshot | Full-size screenshot.

Running remote applications with X11 takes up a lot of network bandwidth, so a broadband (or direct ethernet) connection is required.

Files can be transferred between your Macintosh and your coxeter account in Terminal using the scp or sftp commands as explained in the Unix and Linux section. However, those who prefer a graphical interface program can try Fugu, an award-winning open source sftp and scp utility by the University of Michigan.

Fugu requires Mac OS X 10.2.3 or higher. The Universal binary (which supports both PowerPC- and Intel-based Macs) is available as a free download. After you download the disk image file and agree to the License, Fugu will be installed in the default save folder that is set by your web browser. You should take the opportunity to move the program file to your Applications folder.

Logged into coxeter using Fugu

After you enter your login information [screenshot], you will be prompted for your password [screenshot]. Once you are logged into coxeter, simply drag and drop the files you wish to transfer between the two computers [screenshot].

If your Macintosh still runs Mac OS 9 or earlier, don't worry; there are still programs available which allow you to access coxeter by ssh.

Running ssh and scp is available by obtaining NiftyTelnet SSH. If you do not require scp or sftp, an alternative program is MacSSH. Both programs are available as free downloads. There are also other programs available for a small fee.

The following is a list of external sites which provide extra information regarding the SSH protocol and the various clients mentioned on this web page. Note that the examples they contain use their hosts, i.e. make sure you use e.g. coxeter.math.toronto.edu instead.

• Getting started with SSH.
• Excellent PuTTY Tutorial.
• MacSSH Tutorial.
• NiftyTelnet Tutorial (and others).
• SSH tutorial from Penn State.
• The Secure Shell Frequently Asked Questions.

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