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Can’t get Passwordless SSH to work – Windows 10 Client / RHEL Cluster

    • JakeBloomfield

      Hi All,

      I'm hoping someone can help me!

      We're currently facing an issue where we cannot initiate a Fluent run using passwordless SSH using the native Windows 10 SSH implementation.

      Info of the setup:

      • Windows 10 20H2 client desktop with lastest ANSYS installation (2021 R2)
      • Linux Cluster with 5 nodes
        • RHEL 7.9 (full up to date)
        • ANSYS 2021 R2 installed in default path /ansys_inc

      I have setup passwordless SSH on the client to all of the nodes (all have the same shared /home directory via NFS) - this works absolutely fine via SSH from the Windows command prompt/PowerShell. For testing purposes, I am just using the first node via "Distributed Memory on a Cluster" option.

      However, when I try to use the Fluent launcher, I get the following error message:

      Permission denied (publickey,gssapi-keyex,gssapi-with-mic,password).
      Error: It seems using ssh requires password for sdlpmcfd01. Please enable passwordless login and try again!

      Here is the remote command we're using to spawn the run (username removed for privacy):

      ssh -l  username

      I have made sure the .ssh/authorized_keys on the nodes have the correct permissions (if this wasn't correct, the passwordless SSH connection via the Windows command prompt would fail).

      Any ideas or thoughts?

      I am happy to try a different connection method for SSH e.g. PuTTY or CygWin.. just need to get this working. We used to have a CentOS client for this which worked without issue.. not sure if the Windows implementation of SSH isn't compatiable.



    • DrAmine
      Ansys Employee
      Can you reach that machine using Putty or plink? plink -k username machine "which fluent"
      This looks like that your IT department should be involved.
      With Putty we usually create the private key. For Open SSH you need to convert to the right format. You need to move the public portion of the key into the Linux "Cluster" (editing ~/.ssh/authorized_keys) (Copy all test from public kay portion to that file). One the windows machines include putty in path, create a new env KEYPATH (path to the key). Then make the tests with plink
      plink -i ÔÇ£%KEYPATH%ÔÇØ linuxlogin@linux_machinename pwd.
      If all works, Fluent Use Remote Linux Nodes, Remote Working is a Linux HOME Directory Remote Spwan Command (other: plink -i "Full Path Directory where the key is stored) -l username Head Node is the Linux Head Npde
      I hope it helps.
    • JakeBloomfield
      Hi DrAmine Thanks for your reply.
      I am the IT Manager and I'm looking at this issue on behalf of an engineer (I am not a power user of Fluent, just trying to diagnose this specific connection issue).
      I have yet to use PuTTY or plink as we've been trying to use the native OpenSSH implementation on Windows 10. I will get PuTTY installed and try your instructions to see if I can get anywhere further.
      Cheers Jake
    • JakeBloomfield
      Hi DrAmine I've followed the steps, and I think I've got a bit further. The plink test works and comes back fine (I had to accept the host key manually, as PuTTY doesn't have a way of turning this feature off).
      I've used the command in the Remote Spawn Option as you've specified - it launches fluent, but in the Console it hangs at the following:
      Host spawning Node 0 on machine "" (lnamd64)
      Check your network connections and remote shell configuration.
      If you are on a slow network or running through a scheduler like lsf or sge, you may choose to wait.
      I'll follow up with Commercial Support as I haven't made much headway.
      Cheers Jake
    • DrAmine
      Ansys Employee
      Thanks for the feedback.
      Double check first if you can reach the head node outside of Fluent and report that to the commercial support.
    • gjcdenoga
      I am getting the same errors. It works when I open Fluent on the linux head node of our cluster. However, when I open Fluent on a separate Win10 client and try to solve remotely on the linux head node and the cluster. How was this problem resolved?
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