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Establishing Connections to REPACSS

This document provides detailed instructions on establishing secure remote connections to the REPACSS high-performance computing system at Texas Tech University.

System Access Requirements

Before attempting to connect to the REPACSS environment, users must confirm the following prerequisites:

  • A valid and active TTU eRaider account
  • A properly configured password and Multi-Factor Authentication (MFA)
  • A secure connection to the Texas Tech University (TTU) network, either via wired Ethernet or the GlobalProtect VPN

TTUnet & VPN Requirement

Access to REPACSS is restricted to users connected to the TTUnet network. Off-campus users, and users in buildings with known network limitations (e.g., the Computer Science Department), must use the GlobalProtect VPN.

For assistance configuring VPN access, refer to the following guide:

VPN Required

On Campus:
- You must be connected to TTUnet, either via wired Ethernet or the TTUnet Wi-Fi network.
- Other networks on campus (such as TTUguest or EduRoam) are not supported for direct access.
Off Campus:
- If you are connecting from any other network, including TTUguest, EduRoam, or external internet connections, you must use the TTU GlobalProtect Virtual Private Network (VPN).
- Instructions are available on the VPN Setup Guide.
Authentication: All system access requires secure login via SSH or authorized web-based interfaces.

Note: Users located within the Computer Science Department building may experience restricted access when using TTUnet Wi-Fi. If you encounter connectivity issues, connect via wired Ethernet or enable the VPN to ensure uninterrupted access.

Connecting via Secure Shell (SSH)

Instructions for Windows Users

For users operating Microsoft Windows, it is recommended to install and configure MobaXterm:

  1. Download the installer from https://mobaxterm.mobatek.net
  2. Launch MobaXterm and create a new SSH session with the following details:
  3. Remote Host: repacss.ttu.edu
  4. Username: Your TTU eRaider username
  5. Save and initiate the connection

Instructions for macOS and Linux Users

Users operating macOS or Linux systems can connect via the built-in terminal application:

ssh <your_eRaider_username>@repacss.ttu.edu

Upon successful authentication, the system will display a standard login banner.

Troubleshooting SSH Connections

Authentication Errors

Users may encounter "Permission denied" or "Too many authentication failures" messages due to the following:

  • Incorrect credentials (eRaider username or password)
  • VPN not active or improperly configured
  • SSH client sending too many private keys

Host Key Verification Failed

If you receive a warning that the remote host identification has changed:

  1. Open the file ~/.ssh/known_hosts
  2. Delete the line containing repacss.ttu.edu
  3. Reconnect to the system and manually verify the new host fingerprint when prompted

Additional Assistance

If all configuration steps have been completed and you are still unable to establish a connection, contact the system administrators. Be prepared to provide diagnostic output for further review:

  • Email: repacss.support@ttu.edu
  • Diagnostic Output: Include the result of running the SSH command with the verbose flag: bash ssh -vvv <your_eRaider_username>@repacss.ttu.edu