# USE1 Cluster Operating System

HPC systems are usually accessed via a Linux-based Command Line Interface (CLI).
Via the CLI, users can run programs to manipulate files, load additional software, or execute programs.

While there are many similarities to single-user Linux systems, HPC systems differ widely in the management of provided Software packages, and users must pay attention to the locality of data.

## Learning Outcomes

* Describe the command line interface and the bash shell as well es perform basic commands.
* Use and write basic shell scripts, e.g., to automate the execution of several commands.
* Sketch the organization of the typical file system tree.
* Utilize essential tools to navigate and manage files.
* Understand how to access a Cluster via SSH.
* Understand terminal multiplexers and use them to run longer commands without keeping a connection alive.
* Utilize tools to transfer data between a desktop/laptop system and a remote HPC system.
* Utilize package management tools that provide access to a wide variety of software.
* Demonstrate the usage of an editor to open a file in write mode and save the file and define why CLI based editors are useful in an HPC environment.
* Utilize screen or tmux to preserve a session between logins and classify usecases for these three operations:
    * Creation of a session.
    * Detaching from the current session.
    * Resuming a previous session.
* Illustrate the use of CTRL-Z and CTRL-C in combination with the commands jobs and fg to send the signals SIGINT and SIGTSTP.
* Experiment with the kill command and send the signals SIGKILL, SIGINT, SIGTSTP, also via the numbers instead of the names to a specific process id

## Subskills

* [[skill-tree:use:1:1:b]]
* [[skill-tree:use:1:2:b]]
* [[skill-tree:use:1:3:b]]
* [[skill-tree:use:1:4:b]]
* [[skill-tree:use:1:5:b]]
* [[skill-tree:use:1:6:b]]
* [[skill-tree:use:1:7:b]]
* [[skill-tree:use:1:8:b]]