Connect Remotely with ssh

Secure SHell (SSH) is designed to be a secure way to connect to remote resources from your local machine over an unsecured network. The following example uses an account with username "jolo" using SSH to log into a machine named "foo.edu":

$ ssh jolo@foo.edu

This will open a connection to the remote machine "foo.edu" and log in as the user if authentication is successful. If you log into Stampede3 via SSH, a password and/or private key will be required for authentication. The above example is the most straightforward version of the command, but there are many additional options. For example, to use a key pair (where my_key is the name of the private key file) to login, then the command will look like:

$ ssh -i my_key jolo@foo.edu

Another common option is X11 forwarding, which can be achieved using the -X or -Y flags. X11 forwarding is useful when you are going to use applications that open up outside of the shell. For more information on this and other options, see the man page for ssh.

SSH setup

In order to access a Linux system via ssh, you will need an ssh client and a terminal program on your system. Sometimes these are included in a single application for simplicity. There are many different terminals available, but here are a few examples:

• On Linux, simply open your terminal emulator and enter ssh commands
• On Mac OS, the Terminal app is included with the system, and ssh can be invoked from the command line in the Terminal app
• On Windows:
  • The Linux Bash Shell is available as the Windows Subsystem for Linux and supports many Linux commands, including ssh
  • One commonly-used terminal and ssh client combo is PuTTY
  • Another terminal and ssh client combo is MobaXterm

Securely Copy with scp

Secure Copy Protocol (SCP) is based on the SSH protocol, and is used for securely copying files across the network.

Copy to a remote resource

Say you have a file "code.c" located in your current directory on your local machine that you want to copy to a remote resource in the "Project" directory under your home directory on the remote machine (we'll stick with the user "jolo" and "foo.edu"). This can be done using scp as follows:

$ scp code.c jolo@foo.edu:~/Project

Copy from a remote resource

Alternatively, if you want to copy the file "output.txt" from a remote resource located in the "Project" directory to the directory "Results" on your local machine and rename the file to "Run12_data.txt" during the move:

$ scp jolo@foo.edu:~/Project/output.txt ./Results/Run12_data.txt

Similar syntax can be used to copy from a remote host to another remote host as well. The -r option can be used to copy full directories recursively. For more options, see the scp man page.

SCP setup

To use scp with a remote system, similar to ssh, you will need a program to support it. Here are a few examples:

• On Linux, open your terminal emulator and enter scp commands
• On Mac OS, open the Terminal app and enter scp commands
• On Windows:
  • The Windows Subsystem for Linux supports many Linux commands, including scp
  • From the developers of PuTTY, you can use PSCP
  • MobaXterm comes with a built-in SCP client

If you are expecting to copy large files to or from remote locations, note that File and Directory Compression will be covered later in this tutorial, under Optional Topics.