Create and use an SSH key pair for Rackham

This page describes how to create and use an SSH key for the Rackham cluster.

Procedure

Prefer a video?

• Create and use an SSH key pair for Rackham when outside of SUNET (fails!)
• Create and use an SSH key pair for Rackham on Ubuntu 24.04 Noble (fails!)

This figure shows the procedure:

flowchart TD
  subgraph ip_inside_sunet[IP inside SUNET]
    create[1. Create an SSH key pair]
    add[2. Add your keys to an SSH agent]
    copy[3. Copy the public key to Rackham]
  end
  create --> add
  add --> copy

This procedure will fail if:

• You are outside of the university networks, see how to get inside the university networks. This video shows it will fail when being outside of the university networks
• You use Ubuntu 24.04 Noble, as demonstrated by this video, where a password is still requested after doing this procedure

1. Create an SSH key pair

Create an SSH key pair with the following command:

ssh-keygen -a 100 -t ed25519 -f ~/.ssh/id_ed25519_uppmax_login -C "My comment"

• -a 100: 100 rounds of key derivations, making your key's password harder to brute-force, as is recommended here
• -t ed25519: type of encryption scheme
• -f ~/.ssh/id_ed25519_uppmax_login: specify filename, following the naming scheme as suggested here
• -C "My comment": a comment that will be stored in the key, so you can find out what it was for

2. Add your keys to an SSH agent

Add your newly generated ed25519 key to an SSH agent:

ssh-add ~/.ssh/id_ed25519_uppmax_login

3. Copy the public key to Rackham

Copy the public key to Rackham or other server.

ssh-copy-id -i .ssh/id_ed25519_uppmax_login.pub [username]@rackham.uppmax.uu.se

• -i .ssh/id_ed25519_uppmax_login.pub: the identity file, the public key's filename
• [username]@rackham.uppmax.uu.se: your UPPMAX username, for example sven@rackham.uppmax.uu.se

After this, you can login to Rackham without specifying a password.