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Table of Contents

XRootD access

Setup ALRB and XRootD

The following commands set up ATLAS Local Root Base (ALRB) and XRootD:

$ export ATLAS_LOCAL_ROOT_BASE=/cvmfs/atlas.cern.ch/repo/ATLASLocalRootBase
$ source $ATLAS_LOCAL_ROOT_BASE/user/atlasLocalSetup.sh
$  lsetup xrootd

This gives you access to the xrdcp command.

Obtain a VOMS proxy

To access FAXbox  (read or write) a user must have a valid grid proxy. You may obtain it using these commands (the last command will ask you for the password) :

$ lsetup emi
$ voms-proxy-init -voms atlas

Writing files into FAXbox

Use FAXbox as you normally would access an XRootD system, replacing netid with your own username: 

$ xrdcp -fv output.8g root://faxbox.usatlas.org://user/netid/my-ntuple.ROOT
[xrootd] Total 8192.00 MB  |====================| 100.00 % [116.6 MB/s]

Reading files from FAXbox

As above, FAXbox behaves as a normal XRootD system. Again, replace netid with your own ID:

$ xrdcp root://faxbox.usatlas.org://user/netid/my-ntuple.ROOT my-ntuple.ROOT
[xrootd] Total 8192.00 MB  |====================| 100.00 % [110.2 MB/s]

Accessing FAXbox data from batch submitted jobs

For a batch submitted job to have access to FAXbox data, a valid grid proxy has to be sent with the job. Here an example how to submit a condor job with FAXbox access:

  1. Locate your proxy file:

    $ echo $X509_USER_PROXY
    /tmp/x509up_u20074
    
  2. To your submission script add the line:

    transfer_input_files = /tmp/x509up_u21183
    
  3. To the script that gets executed at the worker node add the line:

    export X509_USER_PROXY=x509up_u21183
    

POSIX access

While logged into login.usatlas.org via ssh, you can access files in your FAXbox folder through the /faxbox path, replacing netid with your own username:

$ ssh netid@login.usatlas.org
Last login: Fri Feb  7 18:35:50 2014 from bikeshed.us
Welcome to ATLAS Connect.
For registration or login problems:  support@connect.usatlas.org
ATLAS Connect user forum:  atlas-connect-l@lists.bnl.gov
For additional documentation and examples: http://connect.usatlas.org/
$ ls -l /faxbox/user/netid 
total 3840
 168 -rw-r--r-- 1 xrootd xrootd  171807 Feb 13 06:26 77353738.zip
  44 -rw-r--r-- 1 xrootd xrootd   41867 Feb 13 05:42 atlas-little-globe.png
   4 -rw-rw-rw- 1 xrootd xrootd     181 Jan 24 19:21 chmod-test
   4 -rw-r--r-- 1 xrootd xrootd    3030 Dec 10 15:35 frontpage.html
3592 -rw-rw-rw- 1 xrootd xrootd 3675430 Feb 13 05:45 mercurial-2.5.3-2.src.rpm
   0 drwxr-xr-x 2 xrootd xrootd      23 Jan 17 10:58 user.ivukotic.rootd.PSNC/
  16 -rw-rw-rw- 1 xrootd xrootd   15204 Feb 14 17:36 whee
   4 -rw-r--r-- 1 xrootd xrootd    1356 Jan 24 19:10 xrootd777.c
   4 -rw-r--r-- 1 xrootd xrootd    2688 Jan 24 19:10 xrootd777.o
   4 -rwxr-xr-x 1 xrootd xrootd    3666 Jan 24 19:10 xrootd777.so*
$ ls -ld ~/faxbox
0 lrwxrwxrwx 1 root users 16 Feb 21 14:39 /home/netid/faxbox -> /faxbox/user/netid/
$ cd faxbox
$ ls -l
total 3840
 168 -rw-r--r-- 1 xrootd xrootd  171807 Feb 13 06:26 77353738.zip
  44 -rw-r--r-- 1 xrootd xrootd   41867 Feb 13 05:42 atlas-little-globe.png
   4 -rw-rw-rw- 1 xrootd xrootd     181 Jan 24 19:21 chmod-test
   4 -rw-r--r-- 1 xrootd xrootd    3030 Dec 10 15:35 frontpage.html
3592 -rw-rw-rw- 1 xrootd xrootd 3675430 Feb 13 05:45 mercurial-2.5.3-2.src.rpm
   0 drwxr-xr-x 2 xrootd xrootd      23 Jan 17 10:58 user.ivukotic.rootd.PSNC/
  16 -rw-rw-rw- 1 xrootd xrootd   15204 Feb 14 17:36 whee
   4 -rw-r--r-- 1 xrootd xrootd    1356 Jan 24 19:10 xrootd777.c
   4 -rw-r--r-- 1 xrootd xrootd    2688 Jan 24 19:10 xrootd777.o
   4 -rwxr-xr-x 1 xrootd xrootd    3666 Jan 24 19:10 xrootd777.so*

 

Note that all files are owned by the xrootd user and group, and are world-readable and -writable. This may seem unusual, but it is normal for the way that FAXbox is set up at this time.  Future updates will allow individual file ownership, but for now all files are anonymized to the xrootd user.

Globus Transfer Access

A public Globus endpoint has been created for FAXbox.  It is named connect#faxbox, and anyone with an ATLAS Connect account may use this endpoint to transfer data in and out of FAXbox.  The top level folder visible through the Globus Transfer user interface is the /faxbox directory from the POSIX view.  It corresponds to the // path in a root:// URI.

 

Demonstration

For this demonstration we will:

  1. Log into the ATLAS Connect portal;
  2. Install Globus Connect Personal;
  3. Create a file on the Macintosh Desktop and initiate a Globus Transfer to copy it to FAXbox;
  4. Set up ALRB and FAX, then use xrdcp to copy that file from FAXbox to login.usatlas.org;
  5. Modify the file and transfer it back via xrdcp;
  6. Copy the modified file back to the Macintosh through another Globus Transfer.

The demonstration is an 8-minute screencast video.

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