01_logging_in.md

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Connecting to CSC Supercomputers {.title}

This topic is about how to login to the CSC supercomputers.


All materials (c) 2020-2025 by CSC – IT Center for Science Ltd. This work is licensed under a **Creative Commons Attribution-ShareAlike** 4.0 Unported License, [http://creativecommons.org/licenses/by-sa/4.0/](http://creativecommons.org/licenses/by-sa/4.0/)

Login via the web interfaces

• A simple way to login to the Puhti supercomputer is via https://www.puhti.csc.fi

• Use your CSC username and password

• The web interface can be used, e.g., to launch GUI applications, browse files or open a command-line shell

  • The latter is useful if your computer does not have an SSH client, but you need command-line access to the supercomputer

• Similar web interfaces are also available for Mahti and LUMI

  • More in-depth documentation in Docs CSC and Docs LUMI

Login with SSH

• SSH is a terminal program that gives you command-line access on the CSC supercomputer

• It is a versatile main interface to a supercomputer

  • Laptop ↔ Toyota, Supercomputer ↔ F1. F1 needs a specialist interface.

• Please read this page for an introduction on how to log in with SSH

  • Example: ssh [email protected]

  • Mac and Linux have SSH. On Windows, PowerShell can be used, but we recommend the web interfaces, or clients like MobaXterm or PuTTY

• Plain SSH will not allow displaying remote graphics

  • The web interfaces are often best for this, but can be enabled also by X11-tunneling (additional installations required on Windows, see link above)

Moving files between a local computer and Puhti

• scp and rsync are powerful command-line tools to copy files

  • scp works even in Windows PowerShell (but rsync is missing)

  • e.g. scp filename [email protected]:/scratch/project_xxxx

  • e.g. rsync -r foldername [email protected]:/scratch/project_xxxx

  • rsync exists in MobaXterm but it removes write permissions of copied files

• Sometimes a GUI tool for transferring files is more convenient

  • Nice tools are e.g. FileZilla and WinSCP (may require admin privileges)

  • MobaXterm also has a file transfer GUI (Tip: first, set persistent home directory)

  • The web interfaces can also be used to easily upload/download files

Setting up SSH keys

• Using SSH keys is easier and safer than using a password with every login

  • A key pair is created and the public key is uploaded to the supercomputer

• SSH keys can be easily used in Windows, Mac, Linux

• Consult our tutorials on how to set up SSH keys for your account

  • Logging in to LUMI requires setting up an SSH key pair and registering the public key in MyCSC

  • Adding SSH keys in MyCSC for Puhti and Mahti is also possible, but not yet a requirement for connecting