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CSD3 access

CSD3 is the University's high-performance computing service, operated by Research Computing Services. Its documentation is the reference for every question of accounts, logins and second factors; the lecture 1 notes give the course's own procedure (sections Remote machines and Course environment), and this page maps the failures seen in the first weeks to the relevant pages of that documentation.

Reference pages

Before the first login

  • An account exists only after the HPC account application form has been processed. The route for the MPhil is announced by the course organisers. A CRSid alone gives no access, and login attempts before the account exists fail.
  • The username is the CRSid and the password is the University password, the one used for Raven. The password can be changed with passwd on a login node, which makes it differ from the University password; the course does not recommend this.
  • The second factor is a six-digit code from an authenticator application, set up once on multi.hpc.cam.ac.uk as in the lecture 1 notes and in the SSH walkthrough. The entry in the application is named CSD3: SSH Login. Login-Web has a separate second factor, named CSD3: <crsid>.

Symptoms

Symptom Explanation Reference
The first ssh shows a fingerprint and asks yes/no. The client does not know the server yet. The fingerprint is compared with the published ones and the answer is yes, not y. All CSD3 login nodes share one set of host keys, so known_hosts may already list it under other names. Host keys
multi.hpc.cam.ac.uk prints a message and closes the connection after the password, with no QR code. The second factor is already configured for the account: multi only serves the one-time set-up. Logins go to login-icelake.hpc.cam.ac.uk. If the password itself was refused, the account may not exist yet (see above). MFA, step 2
The QR code is garbled or broken by blank lines. The QR code and a secret key are printed together: the key can be typed into the application instead (Google Authenticator "Enter a setup key", Microsoft Authenticator account type "Other"). On macOS, export LANG=en_GB.UTF-8 before the ssh avoids the problem. If neither the code nor the key could be used, the secret has to be reset by the service desk before a new attempt. MFA, step 3, MFA FAQ
Connection refused from multi or a login node. Three failed authentications in a row block the client address for twenty minutes. Nothing is gained by retrying before then; the credentials are the same as for login.hpc.cam.ac.uk. MFA FAQ
The six-digit code is always rejected. The code comes from the wrong entry: CSD3: <crsid> is the Login-Web factor, CSD3: SSH Login the SSH one. In Microsoft Authenticator the account must be of type "Other", not "Personal" or "Work". MFA FAQ
The phone was lost or replaced; the emergency codes are gone. The service desk resets the secret after an identity check by video call, from a request sent from the e-mail address registered with the account. MFA, reset
ssh csd3 answers Could not resolve hostname csd3. csd3 is not a host name but an alias defined in ~/.ssh/config on the laptop, as in the lecture 1 notes. The file is per machine and per user; without it, the full address <crsid>@login-icelake.hpc.cam.ac.uk works. Lecture 1 notes, section Remote machines
VS Code Remote-SSH asks for the code twice, or again and again. VS Code opens two connections per window; through the balanced address they can reach different login nodes, and each asks for a code. Connection sharing with ControlMaster in ~/.ssh/config makes later connections reuse the first; the notes add remote.SSH.showLoginTerminal and remote.SSH.useLocalServer. MFA, connection sharing, lecture 1 notes, Troubleshooting
scp or rsync to CSD3 asks for a password and a code at every transfer. Transfers over SSH authenticate like a login; connection sharing applies to them as well. The service also offers Login-Web's file browser and the RDS gateway rds.uis.cam.ac.uk. Connecting, file transfers

Writing to the service desk

Account state, a second factor that was never completed, a reset and a blocked address are matters for the service desk, not for the course or its assistant. Each request is a new e-mail to support@hpc.cam.ac.uk (a reply to a closed ticket may be missed), sent from the address registered with the account, with the CRSid, the exact command typed, the complete message printed and the time of the attempt. The desk operates 09:00–17:00, Monday to Friday.