Pre-workshop checklist

Learning Objectives

  • You will be ready for the workshop!

Please read and try the following steps before arriving. For some of the steps the solution requires waiting for a day or so. So please try them before arriving and try to fix what ever does not work.

  • Follow this guide before arriving; we will not have 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, so you will need to bring a computer. There will be no machines for you to use in the room.

  • Follow all the steps using the computer you plan to bring, not your desktop or someone else’s computer.

  • 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.

  • Please bring your power supply, as well as a plug adaptor to Swiss and European plugs.


In the following we assume you use Mac OS X or Linux. If you are running Windows, step 2 is replaced by a list of instructions given at the bottom of this page.

Try the following steps with the computer you will use at the workshop:

  1. In your browser try and access the web-based book keeping. If you need help with your grid certificate there is the Grid certificate FAQ and you can ask questions on

  2. From a terminal (xterm on Linux or Terminal on Mac OS X) connect to lxplus with ssh -X If your local username is different from your lxplus one use ssh -X 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.

  3. Once connected, check your grid certificate works by typing lhcb-proxy-init. If you need help with your grid certificate there is the Grid certificate FAQ and you can ask questions on lhcb-proxy-init will ask you for the password of your grid certificate and then print something like:

Generating proxy...
Enter Certificate password:
Added VOMS attribute /lhcb/Role=user
Uploading proxy for lhcb_user...
Uploading proxy for private_pilot...
Proxy generated:
subject      : /DC=ch/DC=cern/OU=Organic Units/OU=Users/CN=thead/CN=667505/CN=Timothy Daniel Head/CN=proxy/CN=proxy
issuer       : /DC=ch/DC=cern/OU=Organic Units/OU=Users/CN=thead/CN=667505/CN=Timothy Daniel Head/CN=proxy
identity     : /DC=ch/DC=cern/OU=Organic Units/OU=Users/CN=thead/CN=667505/CN=Timothy Daniel Head
timeleft     : 23:53:59
DIRAC group  : lhcb_user
path         : /tmp/x509up_u25636
username     : thead
properties   : NormalUser
VOMS         : True
VOMS fqan    : ['/lhcb/Role=user']

Proxies uploaded:
 DN                                                                                 | Group         | Until (GMT)
 /DC=ch/DC=cern/OU=Organic Units/OU=Users/CN=thead/CN=667505/CN=Timothy Daniel Head | lhcb_user     | 2015/08/25 08:05
 /DC=ch/DC=cern/OU=Organic Units/OU=Users/CN=thead/CN=667505/CN=Timothy Daniel Head | private_pilot | 2015/08/25 08:05
  1. Check that X11 forwarding works by typing display on lxplus. A wizard should appear in a new window.

    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!

Using Bash

The Bash shell will be used throughout the workshop. The default for new LHCb 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 LHCb, by visiting the 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.

Windows-specific Instructions

On Windows, some additional steps are required before you can connect via SSH.

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

  1. Download the Xming installer.

  2. Run the installer.

  3. Download PuTTY.

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

  1. Start PuTTY.

  2. In the list on the left, unfold Connection and SSH, then click the X11 item.

  3. In the window that appears, make sure the check box labeled Enable X11 forwarding is checked.

  4. Return to the previous window by selecting Session int he list on the left.

  5. In the text box labeled Host Name (or IP address), type

  6. Make sure the Port text box contains the number 22.

  7. Click the Open button on the bottom of the screen.

  8. A window appears with the text login as:. Type your CERN username, followed by Enter.

  9. The window should say Using keyboard-interactive authentication. Password:. Type your password, again followed by Enter.

  10. You now have a remote SSH session at an lxplus server node!