Remotely executing StarCCM+

Linux

(UNIX Systems such as Linux, MacOS, BSD)

StarCCM+ uses two different programs to run simulations, a client and a server. On the server all the simulation task, computations and heavy post processing is executed. The client allows graphical interaction with the server which does not have a GUI. Fortunately, these two programs don't need to run on the same computer. It is possible to start a StarCCM server on a more powerful computer while running a client on a thin computer. The powerful (remote) computer can be anywhere as long as you have a network connection to that computer. We'll assume the remote computer runs Linux. Although possible, the case of a remote windows machine is not covered here (Feel free to add it).

Using a remote computer involves the program ssh. It is used to connect and control the remote computer. Obviously, you need access, too. Usually an account with known password on the remote linux computer is enough.

The first step for setting up StarCCM for remote connections is to configure a passwordless ssh connection. The next step is opening up a StarCCM server on the remote computer. Finally, the client connects to the server.

Setting up SSH

This process is extensively explained on this page Remote Connection Guide.

Focus on these sections:

  • Create a key pair on the remote computer and add it to the remote computer. This will allow passwordless access to compute nodes.
    This step is only necessary if this step wasn't already done according to Step one.
    1. Log into the remote computer.
    2. Create a second keypair. Press enter three times after running this command:
      ssh-keygen
    3. Add the new key to authorized_keys:
      cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

Starting a StarCCM server

Working on a remote computer, typically means, that there is no graphical interface available, such as an explorer, or a start menu. For this reason, StarCCM - and any other program - has to be run via command line. How to do this is explained here: StarCCM+ jobs on the Opti-Cluster

Cleaning the remote computer

StarCCM has a habit of leaving lost processes on a computer. Moreover, an unexperienced user might start servers without being able to interact with them. Therefore, some methods will be described on how to check and how to remove unwanted and lost processes.

FIXME will be added any time soon.

Windows Systems

Source: Steve Portal

StarCCM+ has been designed with a client-server architecture, meaning that the process which does the heavy computation (server) can be on a different machine then the process with which the user interacts (client). Additionally, these two processes do not need to be running on the same operating system, which means that a user can have the client running on a Windows machine while the server is running on a Linux cluster, among other possibilities. One of the requirements to make this work is a passwordless ssh connection between the two machines being used.

Setting up the SSH connection in a homogenous Linux environment is relatively straightforward. If one wants to run the client on a Windows machine, there is a need to install an SSH client since Windows does not have contain one natively. While there are a few options (openSSH and Cygwin), this article will describe the procedure when using the PuTTY tool.

PuTTY

Setting up PuTTY

In order to add the ability to StarCCM to connect to a remote computer set up your PuTTY program as it is explained here: putty

  1. Make sure that you have Pageant running with the loaded key whenever using StarCCM to remote connect. That's the only way to tell StarCCM which key to use when running PuTTY. It
  2. Some settings have to be done in StarCCM, too. Start a StarCCM+ client. Open the Menu Tools>Options. In SSH tunnel, change the SSH tunnel command to PuTTY.
  3. Now launch a StarCCM+ server process on the remote computer, see here.
  4. In the (local) StarCCM client, open the menu File and press “Connect to Server” .
    For the PC-Cluster and Neumann activate the SSH Tunnel.
    Enter the credentials for the remote cluster and chose the node and port where your simulation is running
    You'll find the node and port within the first lines of the StarCCM+ output (e.g. Server::start -host ws05.clus:47827).
    See the example in the screenshot for the PC Cluster.
  5. Optionally, upload files to the remote computer. See the Remote Connection Guide to get some information on how to do this.
  6. Create a key pair on the remote computer and add it to the remote computer. This will allow passwordless access to compute nodes.
    This step is only necessary if this step wasn't already done according to Step one.
    1. Log into the remote computer.
    2. Create a second keypair. Press enter three times after running this command:
      ssh-keygen
    3. Add the new key to authorized_keys:
      cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

Note that ssh was set up only in a single direction, from the Windows machine to the Linux machine. In order to set up the reverse direction, an ssh server must be running on the Windows machine which is not trivial to set up. Consider connecting from Linux to Windows over SSH as not possible.

The PuTTY Manual can be found at, http://the.earth.li/~sgtatham/putty/0.62/htmldoc/

Common errors manual


This problem can raise from many problems: 3 were detected and solutions are suggested

1. As said in this message, the host name you entered (ws,sever,node) or the port (47827) is wrong, please double check that you have the right host name and port number.

2. Configuration: Simulation launched from a workstation or server manually.
Impossible to view a simulation running on the pc-cluster from another computer with SSH connection set up
If your SSH connection is well set up, the problem may come from the below fact:
You had forgotten to set the server connection mode on Collaboration (instead of by default) when you loaded your simulation.

Solution: In the bottom of the displayer in the command part, it is possible to see that by changing the server connection mode from Default to Collaboration involves the addition of the below term in the command:

$ -collab

This addition term is necessary in the command line otherwise you won´t be able to open the simulation from another computer.

3. Configuration: Simulation launched with batch mode.
The problem may raise from the saved sessions in the puTTY configuration.
Check when loaded the session IP adresses, that they are well saved with the automatic browsed private key.
Go to the end page of the below link in the category PuTTY, sub-category Forward the SSH key to the remote computer. Remote Connection Guide

Error message

 The server's ssh-ed25519 key fingerprint is:
ssh-ed25519 256 0e:6f:e5:41:4f:d1:36:42:8a:03:0f:41:0d:23:64:99
Connection abandoned.

Configuration: Simulation launched with batch mode.
Impossible to view a simulation running on either the pc-cluster or Neumann from another computer with SSH connection set up

In this case, the problem comes from the connection between the local computer and the remote server.
Indeed, it means that the remote server doesn´t recognize the local computer. So the connection abandoned.
Why ? Because no connection between each of them was once set up !

Solution: You need to go at the end page of the below link in the category PuTTY, sub-category Forward the SSH key to the remote computer.
Remote Connection Guide

guide/starccm/remote_starccm.txt · Last modified: 2018/11/20 12:33 by seengel
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