# USE1.4 Remote Access

An HPC system is accessed remotely and has its particular file systems that contain data and programs to execute.
Learning the ways of general interaction with the remote system and the tools involved is essential for newcomers.

Users must connect to an HPC system typically using the Secure Shell (SSH), which then starts a shell and allows the interactive access.
When the user disconnects, such a session is terminated.
Data transfer between a local user system (e.g., desktop or laptop) and a remote system requires special tools. 
Interactive access is also allowed.

The tools discussed here are generally valid for systems using Linux, Mac, Windows, and also mobile devices.

## Requirements

* [[skill-tree:use:1:1:b]]

## Learning Outcomes

* Describe how SSH-authentication works:
    * Password authentication.
    * Public-key authentication.
    * The role of an authentication agent and the security implications.
* Generate an SSH public/private key under Linux.
* Register a key for public-key authentication using ssh-copy-id or other local methods.
* Perform a remote login from Linux using SSH.
* Use SSH-agent or equivalents.
* Use Agent forwarding to connect to a third HPC system from an HPC system that you logged into with ssh from your computer.
* Know when to use and how to create a config file.
* Utilize tools to transfer data between the local and remote system:
    * scp
    * sftp
    * rsync (-avz)