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Fix SSH host key error for Tux

Introduction

Mac Terminal or Putty or another SSH client or command-line SSH or SCP should be able to connect as normal to Tux. You will need to accept a new host key when connecting. If you have trouble accepting it or the RSA key, or get an error about a key or RSA key, try the following.

Windows

  1. In cmd.exe or Powershell, type in:
    cd C:\Users\username\.ssh
    Where username is your username on the computer you are using.
    You can also click folders in File Explorer to get to above.
  2. Open known_hosts file.
  3. Inside the known_hosts file, you need to remove all lines that say tux.cs.drexel.edu, tux, or tux with a number after it. It might be all on *one* line, separated by commas. You can just delete the entire line.
  4. Once you remove those and save the file, you will be able to connect and accept the new host keys.

Mac

  1. Go to /Users/username/.ssh where username is your account name on your Mac. To go to the .ssh folder, once you are in /Users/username/ press Command + Shift + '>/.' key which will show the hidden folders on your Mac
  2. Open the file 'known_hosts' in /Users/username/.ssh using textedit.
  3. Remove any lines that say tux.cs.drexel.edu, tux, or tux with a number after them. Make sure that you remove the full line.
  4. Save the file and try connecting again.
  5. Accept a new host key when it prompts after entering password and username.

Linux

  1. Run the command ssh-keygen -f "/path/to/.ssh/known_hosts" -R "tux.cs.drexel.edu"

    The path is often ~/.ssh/known_hosts, but may change depending on your system.
    You may also need to remove "tux" and "tuxN", where N is a number from 1-5, depending on which machines you've connected to before.

  2. Connect to Tux again.
  3. Accept the new Host Key.
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