[[PageOutline]]
= Terminals and Shells = 

[[Image(univac_1965_2.jpg, center, 10%)]]


 ''Taken from UNIVAC promotional materials circa 1960''

The terminal has been the primary means of interfacing with a cluster computing machine since the 1960s. Today, users who are working on a laptop or desktop with an operating system that is based on Unix will have a useful terminal built into their operating system. This includes anyone using Mac os X or any flavor of Linux. 

== Mac Terminal ==

To access the terminal program on a Mac go to 

''Applications -> Utilities -> Terminal''

[[Image(utilities_terminal.png​, center, 20%)]]


This will launch a terminal containing a UNIX shell. The UNIX shell is a command line interpreter which both allows you to pass commands to the operating system and displays output. Currently, the default shell for most unix-based systems is the Bourne Again SHell or bash shell. Your shell can be modified to provide a custom environment and we will go into detail on how to make these modifications in later sessions.

[[Image(terminal.png​, center, 20%)]]

== Ubuntu Terminal == 

In Unity versions of Ubuntu (11.04 and later) the easiest way to access the terminal is through the search function of the dash

''Dash -> Search for Terminal''

[[Image(ubuntu_terminal.png, center,20%)]]

[[Image(terminal2.png, center,20%)]]

== Windows "Terminal" (Command Prompt) ==
=== Evaluate your ssh installation ===

For the following, open a terminal window by locating the Windows search box in the taskbar at the bottom of the screen and entering the command '''cmd'''.

|| [[Image(WindowsSearchBox.png, center, 50%)]]||[[Image(WindowsCommandPrompt.png, center, 50%)]] ||

Check that '''ssh''' is installed by entering the command '''where ssh''' at the command prompt (user@localhost>) in your terminal window.

{{{
user@localhost> where ssh
}}}

If '''ssh''' is installed, then your result will look like the following.

{{{
C:\Users\user\ssh
C:\Windows\System32\OpenSSH\ssh.exe
}}}

If per the above you have '''ssh''' installed, then you should still test that your version of '''ssh''' will work with Cypress, in which case you may still encounter an error. To test your installed '''ssh''' with Cypress, see the section [#SecureSHellSSH Secure SHell (SSH)] below.

Otherwise, if you encounter an unsuccessful result (for example if your result for '''where ssh''' above is "...Could not find..."), then proceed to the appropriate section below for your version of Windows.

=== Windows 11 ===

==== Install OpenSSH ====

To install OpenSSH, see [[https://docs.microsoft.com/en-us/windows-server/administration/openssh/openssh_install_firstuse | Install OpenSSH for Windows]]. Then verify '''ssh''' via [#Evaluateyoursshinstallation Evaluate...] above for use with Cypress.

=== Windows 10 ===

==== Update Options ====

If your Windows 10 does not have the '''ssh''' command or, for example, does not have the proper key exchange method mentioned above, then you can do one of the following.

1. Download and run Windows 10 Update Assistant and then verify '''ssh''' via the above. See [[https://www.microsoft.com/en-us/software-download/windows10|Download and run Windows 10 Update Assistant]].
2. See [#InstallOpenSSH Install OpenSSH] above (applies to Windows 10 as well) to install and verify '''ssh''' for use with Cypress.
3. Proceed to the next section '''Check your OS build number''' to check your OS build number and, if applicable, install Windows Subsystem for Linux (WSL).
4. Proceed to the section [#PuTTY PuTTY] below to install PuTTY.

==== Check your OS build number ====
To find your PC's architecture and Windows build number, go to the Windows search box and open
Settings > System > About

[[Image(https://docs.microsoft.com/en-us/windows/wsl/media/system.png, center, 800px)]]

If your windows 10 is newer than build 16215, you can install WSL with the instructions below.
If your windows 10 is older than build 16215, you can still use [#PuTTY PuTTY].

==== Installing Windows Subsystem for Linux (WSL) ====
1.Open !PowerShell as Administrator by right-clicking on the start button and selecting the menu item '''Windows !PowerShell (Admin)'''

[[Image(startContextMenu.png, center)]]

[[Image(powerShell.png, center, 30%)]]

2.In the resulting window run the command:

{{{
Enable-WindowsOptionalFeature -Online -FeatureName Microsoft-Windows-Subsystem-Linux
}}}

3.Restart your computer when prompted.

4.Let's install Ubuntu, click the link below.

* [[https://www.microsoft.com/store/p/ubuntu/9nblggh4msv6|Ubuntu]]

From the distro's page, select "Get"

[[Image(https://docs.microsoft.com/en-us/windows/wsl/media/ubuntustore.png, center, 500px)]]

5.Open a command-line window, (search '''cmd''') then type 'bash'

[[Image(setWSL.png, center)]]

See [[https://docs.microsoft.com/en-us/windows/wsl/install-win10|Install WSL]]

==== X WIndow for Graphics ====
To run software with graphics with either Windows Terminal or WSL, you have to have X-window client software installed on your Windows. See [[https://wiki.hpc.tulane.edu/trac/wiki/cypress/SshUsage#Windows|here]].

And you may need to do following on WSL terminal.
Under bash command-line window
{{{
sudo apt install x11-apps
}}}
Add a line below into ~/.bashrc
{{{
export DISPLAY=localhost:0.0
}}}

=== Windows 8 ===

As Windows 8 is NOT a Unix based OS, it lacks a native terminal emulator that is capable of providing a Unix shell. This will require a work around. For our requirements, the most common solution is the installation of an open source terminal emulator called PuTTY that supports the communication protocols discussed below. If you are using a Windows machine and you have not already downloaded PuTTY you should do so now. See [#PuTTY PuTTY] below.

=== Windows 7 (Do not use) ===

As of January 14, 2020, if you're still using Windows 7, this represents a critical security threat to the university network and user data, and your network access will be restricted to internet traffic only. '''Thus you'll be prevented from logging in to Cypress.''' For alternatives, see [https://hr.tulane.edu/content/reminder-windows-7-end-life Reminder: Windows 7 End of Life].

=== PuTTY ===

[[http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html|Download PuTTY]]

[[http://the.earth.li/~sgtatham/putty/0.62/htmldoc/|PuTTY Manual]]

After you've downloaded the PuTTY.exe file, move it to the location you prefer and double click to launch.

[[Image(PuTTY_launch.png, center, 30%)]]

To log onto cypress, enter cypress1.tulane.edu (or cypress2.tulane.edu) into the Host Name field and make sure the port is set to 22. Click on Open and you will be given a login window to cypress.

[[Image(PuTTY.png, center, 30%)]]

= Remote Access =

== A short History ==
Scientists have been performing computations remotely since 1940 when George Stibitz used a Teletype machine to perform remote computations on a Complex Number Machine in New York City from the an AMS conference held at Dartmouth (http://history-computer.com/Internet/Dreamers/Stibitz.html). By 1973, standards were defined for a set of remote access protocols called Telnet which are still in use today. Subsequently (1983), the Berkley Software Distribution (BSD) Unix operating system instituted an alternative protocol called Remote SHell, or rsh. While still available on most systems, rsh is not recommended for common use as it lacks encryption. In 1995, this lack of security lead a researcher named Tatu Ylonen to invent a secure set of protocols after his University was the victim of a sniffing attack. He named his protocols Secure SHell, or SSH, and this has become the default means of remote access for unix based machines world wide.



== Secure SHell (SSH) ==
=== Linux, Mac, Windows 10, and WSL ===
Originally, only users on Mac and Linux workstations had '''ssh''' available on the command line. Afterwards, support for '''ssh''' was added to Windows 10 - initially via WSL (see [#InstallingWindowsSubsystemforLinuxWSL WSL] above) and then directly from the Windows terminal.
To connect to a remote server run the following:

{{{
user@localhost> ssh remoteusername@remotehost.example.com
}}}

The first time you log into a new machine, you will be asked if you trust the server. For instance, the first time you log into Cypress using PuTTY you will receive the following prompt:

[[Image(host_key.png, center, 30%)]]

[[Image(host_key_mac.png, center, 30%)]]

Click on yes (or if using !Mac/Linux/Windows/WSL terminal simply type "yes" at the corresponding prompt). You should now be prompted for the password associated with your remote username. 

For those who have accounts on Cypress, you can connect to cypress by running the command 

{{{ 
user@localhost> ssh tulaneID@cypress.tulane.edu
}}}

and, at the prompt for password, entering the password associated with your tulaneID across Tulane resources. 

{{{ 
user@localhost> ssh tulaneID@cypress.tulane.edu
tulaneId@cypress.tulane.edu's password: 
Last login: Mon Mar 29 11:14:39 2021 from XXX.XX.XXX.XXX
[tulaneId@cypress1 ~]$ 
}}}

After successful login, your current working directory on Cypress will be your home directory denoted by the tilde, ~. (See [[https://wiki.hpc.tulane.edu/trac/wiki/cypress/about#Storage:homedirectory|Storage: home directory]].)


[[Image(https://docs.google.com/drawings/d/e/2PACX-1vSlffILDUxxzh_QpD4M7P5-bY_tCkYNjA9xIYWuUUqz_HBBczQ18o5AWA9OZ5_w5Q0bwQJbdgmUCuMJ/pub?w=594&h=209, center)]]

==== In Case Of Error: Unable to negotiate...no matching host key type found ====

If you encounter the error below:
{{{
user@localhost> $ssh userid@cypress.tulane.edu
Error msg: Unable to negotiate with xx.xx.xx.xx port 22: no matching host key type found. Their offer: ssh-rsa,ssh-dss
}}}
Add the following lines to the file ~/.ssh/config on your local computer.
{{{
Host cypress.tulane.edu
        HostName cypress.tulane.edu
        HostKeyAlgorithms=+ssh-rsa,ssh-dss
        PubkeyAcceptedKeyTypes=+ssh-rsa
}}}

If the file ~/.ssh/config doesn't exist yet on your local computer, you may need to first create the directory ~/.ssh and then create and edit the file ~/.ssh/config.

Also, be sure to enter ''exactly the same'' value for '''!HostName''' in the file ~/.ssh/config as the hostname that you use in your '''ssh''' command.

On Linux, Mac, and WSL, if you prefer, you can do so using the command line in your terminal window via the following.
{{{
user@localhost> cd  # change the current directory to your home directory as needed
user@localhost> mkdir -p .ssh # create the subdirectory .ssh as needed
user@localhost> cd .ssh # change to that subdirectory
user@localhost> nano config # create, as needed, and edit and save the file named config.
}}}
For file editing with nano, etc., see [[https://wiki.hpc.tulane.edu/trac/wiki/cypress/FileEditingSoftware/Example|File Editing Example]].

In the case of nano, you can simply copy and paste the contents into the window and save the result.

For Windows terminal, you can open a window for notepad from the command line via the following.
{{{
C:\Users\user> cd &rem change directory to your home directory
C:\Users\user> notepad .ssh\config
}}}

Again, be sure to enter ''exactly the same'' value for '''!HostName''' in the file ~/.ssh/config as the hostname that you use in your '''ssh''' command.

[[cypress/ssh_public-key_authentication | ssh Public-key Authentication]]

== Tunneling X Windows Session ==

=== Using SSH ===

The '''ssh''' command has a '''-Y''' option to support X window tunneling.

To connect to a remote server with X window tunneling run the following:

{{{
user@localhost> ssh -Y remoteusername@remotehost.example.com
}}}

==== Mac ====

For Mac users, you may have to install [https://www.xquartz.org/  XQuartz].

=== Windows ===

All Windows users - whether using '''ssh''' or PuTTY - will need to download and install X window server/client software.

[[https://sourceforge.net/projects/xming/files/Xming/|Xming]]

[[https://sourceforge.net/projects/vcxsrv/|VcXsrv]]

[[http://www.cygwin.com/|Cygwin]]

[[https://x410.dev/ | X410]]

==== Using PuTTY ====

[[Image(puttyX11.png, center, 30%)]]
With PuTTY - in addition to X window server/client software mentioned above, enable X11 forwarding as shown.

==== Using windows commadline prompt ====
{{{
C:\Users\uid>set DISPLAY=127.0.0.1:0.0
C:\Users\uid>ssh -Y uid@cypress.tulane.edu
}}}

= CHECKPOINT =
== For Workshop ==
Everyone should now have a terminal open and be logged into Cypress. If you are not logged on to Cypress, please raise your hand and someone will assist you.
== In General ==
Once you have a terminal, if you are not logged on to Cypress, please request help via hpcadmin@tulane.edu and someone will assist you.

We will return to SSH shortly, but first we need to discuss [[cypress/BasicLinuxComands|Basic Linux Commands]].

[[cypress/BasicLinuxComands|Next Section: Linux Commands]]