Access to CERN CVS

Access to CVS at CERN

To access the CMSSW code, you will need to use the CVS services at CERN. CVS stands for Concurrent Versions System. It's a free software that enables several developers to work on the same project.

The important thing you have to know before accessing CVS at CERN is that there exists globally two kinds of access to it : authenticated or anonymous. If you only need to get the CMSSW code (using a "cvs co" or "checkout"), then anonymous access is sufficient. But if you need to modify the CMSSW code (doing so called "commit" operations), then you need to go through authentication.

To learn more about how to use CVS services, I strongly advise you to read the following pages :

https://twiki.cern.ch/twiki/bin/view/CMS/WorkBookComputingConcepts#CvsCheckoutModules

http://lcgcvs.web.cern.ch/lcgcvs/howto.php#accessing

Authenticated access from IIHE

SSH access method

You need to set your environment in the following way :

export CVS_RSH=/usr/bin/ssh

export CVSROOT=:ext:<YOUR_USERNAME>@cmscvs.cern.ch:/cvs_server/repositories/CMSSW

You'll be asked for your CERN's account password each time you access the CVS repository with the cvs command.

Kerberos V access method

You need to set your environment in the following way :

export CVSROOT=:ext:<YOUR_USERNAME>@cmscvs.cern.ch:/cvs_server/repositories/CMSSW

Then, you just create your Kerberos access ticket by doing :

kinit

and giving your password.

One practicle thing to notice : with the Kerberos method, your password will only be asked once.

Troubleshooting

If you meet troubles doing the kinit, you can check that the file /etc/krb5.conf contains the following lines :

CERN.CH
CERN.CH afsdb1.cern.ch
CERN.CH afsdb3.cern.ch
CERN.CH afsdb2.cern.ch

and also check that /etc/krb.realms contains the following :

.cern.ch CERN.CH
.wgs.cern.ch CERN.CH
.plus.cern.ch CERN.CH

If it's not the case, contact the IIHE's grid administration team.