Connecting to Roihu

This topic is about how to login to the Roihu supercomputer.

All materials (c) 2020-2026 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/

Login via the web interfaces

  • The easiest way to login to Roihu supercomputer is via roihu.csc.fi
  • Login requires 1) multi-factor authentication (MFA) and 2) a medium or high level of identity assurance (LoA)
  • 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
  • LUMI also has a similar web interface.

Login with SSH (1/3)

  • 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.
  • Logging in with SSH requires SSH keys and a valid SSH certificate
    • A key pair is created and the public key is uploaded to MyCSC
    • The public key must then be signed every 24 hours to obtain a time-based certificate allowing SSH logins to Roihu
    • Read the documentation and do the tutorial
    • Consult the FAQ or contact to troubleshoot issues

Login with SSH (2/3)

  • After adding your public key to MyCSC, you need to sign it to generate an SSH certificate
    • The CSC certificate helper tool is recommended
      • python3 csc_cert.py -u cscusername /path/to/local/public/key
      • Signs the key, downloads the certificate, and adds it to your SSH agent to make logging in easy
      • Python is required on all operating systems
      • Using authentication agent also requires:
        • ssh-agent utility (Linux/macOS/PowerShell/MobaXterm terminal users) or
        • Pageant & WinSCP (PuTTY/MobaXterm GUI users)
    • Alternatively, users can sign and download their SSH certificate manually in MyCSC

Login with SSH (3/3)

  • Roihu has separate login nodes for the CPU and GPU partitions. Once SSH keys and certificate are set up, connect with ssh command:
    • Roihu-CPU: ssh cscusername@roihu-cpu.csc.fi
    • Roihu-GPU: ssh cscusername@roihu-gpu.csc.fi
    • Why? Roihu CPUs and GPUs have different architectures (x86 vs. ARM)
  • Detailed instructions for SSH login on macOS and Linux and on Windows
    • On Windows, we recommend MobaXterm or PuTTY clients, or simply using the web interfaces instead of SSH
  • Note! Plain SSH will not allow displaying remote graphics
    • The web interfaces are often best for this, but a graphical connection can also be enabled over SSH using X11 forwarding

Moving files between a local computer and Roihu

  • scp and rsync are powerful command-line tools to copy files
    • scp works even in Windows PowerShell (but rsync is missing)
    • scp filename cscusername@roihu-cpu.csc.fi:/scratch/project_xxxx
    • rsync -r foldername cscusername@roihu-cpu.csc.fi:/scratch/project_xxxx
  • Sometimes a GUI tool for transferring files is more convenient
    • Nice tools are e.g. FileZilla and WinSCP
    • MobaXterm also has a file transfer GUI (Tip: set persistent home directory)
    • Roihu web interface can also be used to easily upload/download files
  • Note! These file transfer tools (except Roihu web interface) are SSH-based, so using them at CSC requires SSH keys and a valid certificate!

Moving files between Puhti and Roihu (1/2)

  • SSH keys and certificate should only be stored on your local computer
  • To access Roihu from Puhti, you must ensure your local SSH keys and certificate are forwarded to Puhti
    • This is called SSH agent forwarding
    • Allows using e.g. rsync or scp to move files directly from Puhti to Roihu
    • If you want to do the reverse, i.e. access Puhti from Roihu, it is enough to forward your SSH keys since Puhti does not require SSH certificates for authentication
  • It is strongly recommended to use the CSC certificate helper tool to make adding SSH keys and certificate to SSH agent easy

Moving files between Puhti and Roihu (2/2)

  • On Linux/macOS, simply add option -A to your SSH command:
    • ssh -A cscusername@puhti.csc.fi
  • Using MobaXterm:
    • Similar to Linux/macOS if using local terminal, otherwise toggle Allow agent forwarding under “Session” -> “SSH” -> “Advanced SSH settings” -> “Expert SSH settings”
  • Using PuTTY:
    • Select “SSH” -> “Connection” -> “Auth” and toggle option Allow agent forwarding under “Other authentication-related options”