1.1. Pre-workshop checklist

Learning Objectives

You will be ready for the workshop!

Follow this guide before arriving; we will do a quick introduction to environment setup but we will not have much time to help you with problems on these issues during the workshop. This means you will end up watching instead of participating.
This will be an interactive workshop. In all cases (in-person or virtual tutorials) you will need to use your own computer (for in-person events there will be no machines for you to use in the room). You will use your own computer to connect to resources available for the tutorial (check the event announcement for the available options).
Follow all the steps using the computer you plan to bring, not your desktop or someone else’s computer.
In case of a in-person event
- Make sure that you can connect to the network in the room. For example, for events at CERN, if this is the first time you are bringing your laptop to CERN, you will have to register it before it can access the internet.
- Do not forget to bring your power supply, as well as the relevant plug adaptor, e.g., for CERN, to Swiss and European plugs.
The FCCSW is part of the Key4hep software ecosystem has been developed on Linux and the main platform supported is the default platform on CERN lxplus, i.e. CentOS7 . Experimental support for other Linux systems (e.g. Ubuntu 20.04 LTS) is provided as is. Solutions for running on MacOxS are also available and will be presented at the workshop. There is no support for Windows.

1.1.1. Checking the chosen resources

Please try the following steps with the computer you will use at the workshop (the example is given for lxplus, but should hold for the other resources as well):

From a terminal (xterm on Linux or Terminal on Mac OS X) connect to lxplus with ssh -X lxplus.cern.ch. If your local username is different from your lxplus one use ssh -X mylxplusname@lxplus.cern.ch. Please try exactly this command even if you usually use an alias or other shortcut.
If, just below the Password: line, you get a message Warning: untrusted X11 forwarding setup failed: xauth key data not generated:
- Logout (using logout or Ctrl-d)
- Login using -Y instead of -X
- This will switch to trusted X11 forwarding and you may see a message like Warning: No xauth data; using fake authentication data for X11 forwarding.
Check that X11 forwarding works by typing glxgears on lxplus. Some rotating gears should appear in a new window. Press Ctrl-C from the terminal to exit.

If you’re not connected to the CERN network at CERN, do not worry if the X11 forwarding is slow–this is normal.

If you can successfully execute all of the above steps, you are ready to go for the workshop!

1.1.2. Enabling the FCC software ecosystem from `cvmfs`

As mentioned above the FCC software ecosystem is now based and included on the Key4hep software stack which is available on cvmfs and can be set up using:

source /cvmfs/sw.hsf.org/key4hep/setup.sh

For compatibility reasons, the previous way of setting up the software

source /cvmfs/fcc.cern.ch/sw/latest/setup.sh

is still available.

1.1.3. Special notes or alternative cases / settings

1.1.3.1. Bash shell

The Bash shell will be used throughout the workshop. The default for new computing accounts is now Bash. If you have an older account, the default used to be a shell called tcsh (“tee-cee-shell”), which has subtly different ways of doing things in comparison with Bash.

It is recommended to change your default shell to Bash if this is the case, which is much more widely used than tcsh and also supported by FCC, by visiting your CERN account page, then clicking “Resources and services”, then “List services”, “LXPLUS and Linux”, “Settings”, then change “Unix shell” to /bin/bash, and click “Save Selection”.

If you don’t want to change your default shell, just execute the bash command when you login to lxplus.

1.1.3.2. Using a virtual machine through VirtualBox

The CernVM project provides a convenient tool to start VMs, cernvm-launch, and a public repository of contexts to be used with cernvm-launch to configure the VM at your needs. The tool cernvm-launch is available for Linux, Mac and Windows. A context dedicated to the FCC tutorials is available in the repository. The cernvm-launch works with VirtualBox, virtualization manager available for free for all platforms.

If you have a CERN account, this is a convenient way to enable access to the EOS storage system.

To create and use a CernVM virtual machine for the FCC tutorials please follow the following steps:

Make sure VirtualBox is installed (details installing instructions from the product web page).
Download the cernvm-launch binary for your platform either from the dedicated download page or from the following links:
- Linux
- Mac
- Win
Make sure is visible in your $PATH.
Get the fcc-tutorial.context (use wget or curl)

Once you have all this you can create the VM with this command:

$ cernvm-launch create --name fcc-tutorial --cpus 4 --memory 8000 --disk 40000 --sharedFolder /Users/ganis/fcc/tutorial fcc-tutorial.context

You an choose how many CPU cores to use, the memory and the disk space; advise is to use the half of what your host machine has in terms of CPU cores and RAM, while for the disk 40000 should be enough. Good rules of thumb are to use half the cores of your machine, at least 2 GB memory per core, and enough disk for your job. The above command should open a window with VirtualBox and produce on the screen an output like this

Using user data file: fcc-tutorial.context
Parameters used for the machine creation:
        name: fcc-tutorial
        cpus: 4
        memory: 8000
        disk: 20000
        cernvmVersion: 2021.05-1
        sharedFolder: /Users/ganis/fcc/tutorial

It is advised to choose to share the folder where you have our tutorial files, so that you can interchange the VM and the host machine very conveniently.

From now on you can either work in the VirtualBox window or ssh to the machine with

cernvm-launch ssh [username@]fcc-tutorial

The default user name and password are fccuser and xpass; these can be changed in the fcc-tutorial.context file before creating the VM. Graphics is automatically enable when connecting via ssh. Note, however, that GL-related graphics may not work on Mac hosts; for the time being the only workaround is to use directly the VirtualBox desktop.

The user has sudo privileges. Passless ssh connection can be setup as usual but needs to be enabled in /etc/ssh/sshd_config (editable as sudo).

The cernvm-launch also supports listing, stopping, starting virtual machines. Please run cernvm-launch -h for all the available options.

1.1.3.3. Windows

On Windows, some additional steps are required before you can connect via SSH. The following instructions may help in achieving this:

Set up steps (you only have to perform this once):

Download the Xming installer.
Run the installer.
Download PuTTY.

The following steps have to be executed each time you want to connect:

Start PuTTY.
In the list on the left, unfold Connection and SSH, then click the X11 item.
In the window that appears, make sure the check box labeled Enable X11 forwarding is checked.
Return to the previous window by selecting Session int he list on the left.
In the text box labeled Host Name (or IP address), type lxplus.cern.ch.
Make sure the Port text box contains the number 22.
Click the Open button on the bottom of the screen.
A window appears with the text login as:. Type your CERN username, followed by Enter.
The window should say Using keyboard-interactive authentication. Password:. Type your password, again followed by Enter.
You now have a remote SSH session at an lxplus server node!