Getting started with the CMSSW software at IIHE

A few words on our User Interfaces

• The policies for usage of the User Interfaces can be found here. Please read them carefully.

Login to a machine and define the CMS environment variables

• Login to a user interface :

 e.g: 

  ssh -X <tt>whoami</tt>@m1.iihe.ac.be

• Source the CMS environment :

  source $VO_CMS_SW_DIR/cmsset_default.sh

• or for tcsh :

  source $VO_CMS_SW_DIR/cmsset_default.csh

• Adapt your SCRAM_ARCH environment variable :

Keep in mind that this initial source will affect the value of the environment variable SCRAM_ARCH. Depending on which UI you are, SCRAM_ARCH can take two different values : slc4_ia32_gcc345 for UIs in SL4, and slc5_ia32_gcc434 for UIs in SL5. As a practical consequence, if you want to work with CMSSW releases older than CMSSW_3_4_0 on an SL5 UI, than you must change SCRAM_ARCH :

  export SCRAM_ARCH=slc4_ia32_gcc345

If you want to use CMSSW4 releases, then you must set SCRAM_ARCH like this :

  export SCRAM_ARCH=slc5_amd64_gcc434

• Define the code cvs repository :

export CVSROOT=:ext:<your user name>@cmscvs.cern.ch:/local/reps/CMSSW

• or for tcsh :

 setenv CVSROOT :ext:<your user name>@cmscvs.cern.ch:/local/reps/CMSSW

• where you replace <your user name> by your user name at cern, and make a kerberos token :

 kinit

log in with your cern password. 

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Prepare the CMSSW working area

• First, list the CMSSW versions installed locally

  scramv1 list
  scramv1 list | grep CMSSW

These commands also show the paths to the installation directories. 

• Select the version you want to work with (here: CMSSW_2_2_6)
• Install a CMSSW working area, go to the src subdirectory and prepare to compile and run

  scramv1 p CMSSW CMSSW_4_4_5
  cd CMSSW_4_4_5/src
  eval <tt>scramv1 runtime -sh</tt>

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Get the necessary code

• checkout the source code of the libraries that you want to use or modify. Here we will produce a few fastsim ttbar events with production of a PAT-tree in the end:

  cvs co -r CMSSW_4_4_5 PhysicsTools/PatAlgos/test; cd PhysicsTools/PatAlgos/test

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Run CMSSW interactively and produce a few events

The parameters for CMSSW are specified in a text file called the config file. Run it with the command:

  cmsRun patLayer1_fromScratch_fast.cfg.py

You should see one root file appear: PATLayer1_Output.fromScratch_fast.root

At this stage you should learn more about CMSSW and PAT by studying the CMSSW Workbook.

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Troubleshooting

If you meet troubles, please have a look in our FAQ : FAQ CMSSW on the Grid on proxy and more!

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