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SSH: Difference between revisions
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Secure Shell (SSH) is a widely used standard to connect to remote machines | Secure Shell (SSH) is a widely used standard to connect to remote machines securely. The SSH connection is encrypted, including the username and password. SSH is the standard way for you to connect in order to execute commands, submit jobs, check the progress of jobs, and in some cases, transfer files. | ||
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Various implementations of the SSH standard exist for most major operating systems. | Various implementations of the SSH standard exist for most major operating systems. | ||
*On macOS and Linux, the most widely used client is OpenSSH, a command line application installed by default | *On macOS and Linux, the most widely used client is OpenSSH, a command line application installed by default. | ||
*For recent versions of Windows, SSH is available in the PowerShell terminal, in the <code>cmd</code> prompt, or through Windows Subsystem for Linux (WSL). | *For recent versions of Windows, SSH is available in the PowerShell terminal, in the <code>cmd</code> prompt, or through Windows Subsystem for Linux (WSL). There are also 3rd-party SSH clients that are popular, such as [[Connecting with PuTTY|PuTTY]], [[Connecting with MobaXTerm|MobaXTerm]], [https://winscp.net/eng/download.php WinSCP], and [https://www.bitvise.com/ssh-client-download Bitvise]. | ||
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To use any of these implementations of SSH successfully, you need to know | To use any of these implementations of SSH successfully, you need to know the name of the machine to which you want to connect, your username and your password. | ||
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Your <code>username</code> is your <b>default account</b>, typically something like <code>jsmith</code>, and the password is the same one you use to log in to | Your <code>username</code> is your <b>default account</b>, typically something like <code>jsmith</code>, and the password is the same one you use to log in to [https://ccdb.alliancecan.ca/ CCDB]. The <code>username</code> is <b>not</b> your CCI, like <code>abc-123</code>, nor a CCRI like <code>abc-123-01</code>, nor your email address. | ||
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On Linux or macOS, you will need to open a terminal, for example /Applications/Utilities/Terminal.app for macOS, and then use the command: | |||
{{Command|ssh -Y username@machine_name}} | {{Command|ssh -Y username@machine_name}} | ||
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The first time that you connect to a remote machine you'll be asked to store a copy locally of its <i>host key</i>, a unique identifier that allows the SSH client to verify, when connecting next time, that this is the same machine. | The first time that you connect to a remote machine you'll be asked to store a copy locally of its <i>host key</i>, a unique identifier that allows the SSH client to verify, when connecting next time, that this is the same machine. | ||
The option <code>-Y</code> shown above forwards X11 traffic which allows you to use graphical applications on the remote machine such as certain text editors. Note that to use graphical applications you also need to have an X11 server installed on your workstation. Under Linux, an X11 server will normally already be installed, but users of macOS will typically need to install an external package such as | The option <code>-Y</code> shown above forwards X11 traffic which allows you to use graphical applications on the remote machine such as certain text editors. Note that to use graphical applications you also need to have an X11 server installed on your workstation. Under Linux, an X11 server will normally already be installed, but users of macOS will typically need to install an external package such as [https://www.xquartz.org XQuartz]. Under Windows, MobaXterm comes with an X11 server, while for PuTTY users, there is [https://sourceforge.net/projects/vcxsrv/ VcXsrv]. | ||
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Note that when connecting via SSH to one of our clusters you will be randomly assigned to one of several distinct login nodes used for the cluster to balance the connection load, so | Note that when connecting via SSH to one of our clusters you will be randomly assigned to one of several distinct login nodes used for the cluster to balance the connection load, so you may land on a different login node from one connection to another, e.g., <code>cedar1</code>, <code>cedar5</code>, <code>gra-login4</code> or <code>gra-login2</code>. If you use a program like [https://www.gnu.org/software/screen/ screen] to manage your login sessions, you will need to make sure that you are on the same login node to open an older session by making an SSH connection to the appropriate login node from whichever one you initially landed on. For example, if you were assigned <code>gra-login4</code> when you typed <code>ssh username@graham.alliancecan.ca</code> but you want to be on <code>gra-login2</code>, type <code>ssh gra-login2</code> from <code>gra-login4</code> to get there. | ||
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= Connection errors = <!--T:9--> | = Connection errors = <!--T:9--> | ||
While connecting to one of our clusters, you might get an error message | While connecting to one of our clusters, you might get an error message such as: | ||
* no matching cipher found | * no matching cipher found | ||
* no matching MAC found | * no matching MAC found | ||