Grid For Dummies:

A step by step introduction for stupid users like me

Before anything else

Before doing anything else you will have to get a grid certificate: http://grid.desy.de/certs/#_intro_ and become member of an virtual organisation (VO): http://grid.desy.de/certs/#_vo_ .

Once you succeeded with these very first administrative steps, put your certificate into your afs directory. And now you can start to use the grid!

First steps

You can create an shell script to set the grid environment like start_grid.sh

Copy the attached script into your afs directory and execute it:

$ . start_grid.sh

Afterwards you need to initialize a grid proxy

$ voms-proxy-init --voms calice --valid 168:00
$ Enter GRID pass phrase:

And you should get a message like:

Your identity: /O=GermanGrid/OU=DESY/CN=Nanda Wattimena
Creating temporary proxy ........................................ Done
Contacting  grid-voms.desy.de:15102 [/C=DE/O=GermanGrid/OU=DESY/CN=host/grid-voms.desy.de] "calice" Done
Creating proxy .................................................... Done
Your proxy is valid until Wed Mar 19 14:47:18 2008

This proxy will be valid for the VO calice (voms = virtual organisation membership service) for the next 168:00 hours, so practically for ever.

In case you want to check your proxy just type:

$ voms-proxy-info -all

Once you are done don't forget to destroy your proxy! Otherwise other people might abuse it.

$ voms-proxy-destroy

Getting informations

To have a look what is available try

$ lfc-ls /grid/calice/tb-cern/sim/test_prod

to list a file cataloge, or

$ lcg-infosites --vo calice ce
$ lcg-info --vo calice  --list-ce --attrs TotalCPUs,MaxCPUTime,MaxWCTime

for informations about info about computing elements (CE), sites, ...

Copying from / to the Grid

To get a file from the grid:

$ lcg-cp -v --vo calice lfn:/grid/calice/tb-cern/rec/rec_v0405/log/therec.steer.321071.tar.gz file:$PWD/therec.steer.321071.tar.gz

This will copy the file therec.steer.321071.tar.gz from the grid path therec.steer.321071.tar.gz to your current directory.

To put a file into the grid:

$ lcg-cr -v --vo calice -d srm://srm-dcache.desy.de/pnfs/desy.de/calice/tb-cern/sim/test_prod/desy/Mu_100GeV_100000evt_TBCern07.tgz -l lfn:/grid/calice/tb-cern/sim/test_prod/desy/Mu_100GeV_100000evt_TBCern07.tgz file:/pool/nwattime/Mu_100GeV_100000evt_TBCern07.tgz

This will put the file: Mu_100GeV_100000evt_TBCern07.tgz from the directory: /pool/nwattime/ to the DESY dCache: /pnfs/desy.de/calice/tb-cern/sim/test_prod/desy/ and make it available from the Grid path: /grid/calice/tb-cern/sim/test_prod/desy/

Instead of specifying a certain file and directory on the dCache, you can also specify the storage element only. This means you can use the option '-d srm-dcache.desy.de' instead of '-d srm://srm-dcache.desy.de/pnfs/desy.de/...'. In this case the file is stored in a generic directory (srm://srm-dcache.desy.de/pnfs/desy.de/calice/generated/<date of copying: yyyy-mm-dd>). Its file name is changed to some automatically generated combination of letters and numbers.

Running jobs on the grid

In case you really managed to run a job on the grid, here are some more useful commands:

$ glite-wms-job-status -i JobID.jid

shows the job status.

$ glite-wms-job-output --noint --dir $(pwd) -i JobID.jid

gives you an output sandbox, and

$ glite-wms-job-cancel --noint -i Mokka.jid

will cancel the job on the CE.