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Support use of xrootd by HEP experiments


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Peter Elmer <[log in to unmask]>
18 Aug 2004 14:39:41 +0200Wed, 18 Aug 2004 14:39:41 +0200
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On Wed, Aug 18, 2004 at 02:25:49PM +0200, Fons Rademakers wrote:
> Yes, I get an error message from TXUrl. Gerri can you maybe check this
> and fix it so that localhost works again in the rootd url?
> Other question, how do I start xrootd so that is assumes relative paths
> to start in the users home directory? Now default is /tmp.

  Which user? The one which started xrootd or the one accessing files?

  xrootd behaves differently that rootd in this respect. It doesn't assume
that paths start in /tmp by default, it only allows access to /tmp by default.
I've recently started to add some example configurations to describe some


but the short answer is that you can export other area (e.g. like /data) with
either a line in the config file:

xrootd.export /data

or by starting xrootd as:

xrootd /data

I don't think it takes a "*" (obviously very insecure).

  There is a separate option "oss.localroot" which allows for a _global_
server side prefix to all paths, i.e. a file at /mnt/temp/path/myfile.root

oss.localroot /mnt/temp

will be accessed as


  I'm not actually surt how it will behave for relative paths:

   root://host:port/myfile.root                    *

or for 

   root://host:port/~/myfile.root                  *

This is what you are asking about, is that correct? Could you remind me
exactly what is done by rootd in the two cases marked with an "*"? (i.e.
relative path WRT what and "~" means which user?)


> On Wed, 2004-08-18 at 11:24, Peter Elmer wrote:
> >   Hi Fons,
> > 
> > On Tue, Aug 17, 2004 at 12:48:43PM +0200, Fons Rademakers wrote:
> > >   the rule in TFile::Open for opening via rootd currently is:
> > > 
> > >     "If the url points to the localhost and the file will be opened in
> > >      readonly mode and the current user has read access or the specified
> > >      user is equal to the current user then open local TFile."
> > > 
> > > This feature is specially important for PROOF where we access files
> > > always via rootd urls (so any worker can access any file) but where the
> > > packetizer optimizes the work so that the workers mostly will get local
> > > files. Using the above feature these local files will be opened directly
> > > as TFile's and won't go through rootd. To force a local file to be
> > > opened via rootd specify as host "localhost". If TXUrl this also
> > > supports then we will have the same behavior. If this "localhost"
> > > feature is supported by netx/xrootd then we can always use that as
> > > "backdoor" to test xrootd on the same machine as where the client runs.
> > 
> >   Yes, the "localhost" option was in fact what Alvise and Fabrizio were
> > using themselves for this purpose. I've still not succeeded in building
> > the HEAD, but is the issue you are seeing related to the "in or out domain"
> > checks? That is what I was seeing with the last XTNetFile version before
> > they began the migration to TXNetFile.

Peter Elmer     E-mail: [log in to unmask]      Phone: +41 (22) 767-4644
Address: CERN Division PPE, Bat. 32 2C-14, CH-1211 Geneva 23, Switzerland