ComputingDocumentation

How to get a Grid User Certificate

* Depending upon the university, research institution or location you have to choose the certification authority
* For USA and other parts of Noth/South America, Open Science Grid (OSG) is the certification authority
* For UK, the equivalent is GridPP
* Follow instructions given here in order to obtain your OSG user certificate. Follow steps 2-5 after going to one of the certification authority sites above.

How to register your Grid Certificate in the LZ VO

* If you already have a grid user certificate, then you would like to \
   register your certificate with LZ VO in order to use its resources
* Using a web browser go to the LZ VOMS server 
  ==> If your browser does not trust the voms.hep.wisc.edu https certificate, follow the instructions here under Installing Certifying Authority certificates into a web browser.
  ==> Use your grid certificate (signature) to authenticate
* Fill in the form with all the information and click submit
* You should receive an email that tells you to confirm the submission
* A VO representative will approve your ticket only after your confirmation

Accessing LZ Storage at Wisconsin

# ssh to the LZ login server at Wisconsin if you have an account there
# we can provide you an account if you need one, send mail to here
# or your machine with access to grid tools
 ssh <login name>@lzlogin.hep.wisc.edu

# create voms-proxy
 voms-proxy-init --voms=lz  ## it will prompt password for you to type

# This will tell you that you are grid user with LZ VO
 gsido whoami  (should return something like lz00x)

# Create your user directory in
 gsido mkdir -p /hdfs/lz/user/<login name>

# Copy files from local directory to the storage area
 gsido cp <some file> /hdfs/lz/user/<login name>

# Copy files using Grid computing copy clients and storage elements
 lcg-cp /tmp/tmpfile -bvvD srmv2 srm://cmssrm2.hep.wisc.edu:8443/srm/v2/server?SFN=/hdfs/lz/user/tapas/tt
 gfal-copy -v file:///tmp/tmpfile srm://cmssrm2.hep.wisc.edu:8443/srm/v2/server?SFN=/hdfs/lz/user/tapas/

Accessing LZ CVMFS repository

# If any of your machines have /cvmfs mounted, then give this a try  :
   ls /cvmfs/lz.opensciencegrid.org 

# Currently, this repository can be written from a machine (lzsoft.hep.wisc.edu) hosted at Wisconsin
  In order to have write privileges please contact us.

Firefox-39.0 Error while accessing VOMS server

* When trying to access voms server web page using Firefox-39.0 one may get the following error message :
            SSL received a weak ephemeral Diffie-Hellman key in Server Key Exchange handshake message. 
             (Error code: ssl_error_weak_server_ephemeral_dh_key)

* The workaround is to do the following:
 1) In FireFox, enter "about:config" in the URL field and press enter. 
 2) Accept the "This might void your warranty!" warning
 3) In the search field at the top, enter "security.ssl3.dhe_rsa_aes" 
 4) Double click each result (128 and 256) to toggle the Value to "false"

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