[tutorial] 🔐 SSH login troubleshooting (key mismatch)

[Yann.Sagon]

SSH login troubleshooting (key mismatch)

If you cannot connect to the Baobab cluster via SSH, it is often due to a mismatch between:

• the private key on your machine
• the public key stored in LDAP

You can easily verify this by comparing their fingerprints.

---

Step 1 — Check your local key

On your computer, run:

ssh-keygen -lf ~/.ssh/id_rsa

(Replace id_rsa with id_ed25519 or your key file if different.)

This will display a fingerprint like:

2048 SHA256:XXXX... yourname@yourhost

---

Step 2 — Check the key stored in LDAP

If you cannot SSH, connect via Open OnDemand:

https://openondemand.baobab.hpc.unige.ch

Open a shell and run:

/usr/bin/sss_ssh_authorizedkeys <your_username> | ssh-keygen -lf -

---

Step 3 — Compare fingerprints

Compare the SHA256:... values from both commands:

• If they are identical → your key is correct
• If they are different → you are not using the right private key. Check in my-account.unige.ch that the key listed there is correct. If this is the case, contact us.

---

Optional debugging

You can also run:

ssh -vvv login.baobab.hpc.unige.ch

---

Common issues

• Wrong key file used
• Key not loaded in ssh-agent
• Multiple keys in ~/.ssh/
• Incorrect SSH config (~/.ssh/config)

---

If you’re still stuck, feel free to post on this forum with:

• your command output
• the error message

It will help others (and us) diagnose the issue quickly.