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== How to install a disk image on the nodes of a Testbed  (using ''imageNodes4'') ==

If you have not done so yet: 

 * [http://www.orbit-lab.org/wiki/Registration Register] for an account
 * [https://www.orbit-lab.org/schedule/ Make a reservation] on the Schedular for a given tesbed

Lets assume that you registered as user 'bob' and made a reservation for the 'grid' testbed. You then access the 'grid' console using the command:

 {{{
  ssh bob@console.grid.orbit-lab.org
 }}}

Then, to image some nodes on the 'grid' testbed, use the command:

 {{{
  imageNodes4 [1..20,1..20] baseline.ndz 
  # will write the 'baseline.ndz' disk image on the entire set of 20x20 nodes on the 'grid'
  
  imageNodes4 [[3,1],[5,6]] baseline.ndz 
  # same as above, but only on nodes [3,1] and [5,6]
 }}}

The output of the "imaging" process will look like the following:

 {{{
 Imaging nodes: '[1..20,1..20]' with image 'baseline.ndz' on default domain (retrieved from hostname)
 INFO init: NodeHandler Version 4.2.0 (1272)
 INFO init: Experiment ID: grid_2007_07_01_21_01_56
 ...
 INFO stdlib: Waiting for nodes (Up/Down/Total): 0/320/220 - (still down: n_1_2,n_1_1)
 }}}

At the end of the "imaging" process, you will have 3 ''topology'' files within your user directory:

 * [wiki:Tutorial/HowToImageSampleTopo_grid_active topo_grid_active.rb] - a ''topology'' with all the nodes that have successfully been imaged 
 * [wiki:Tutorial/HowToImageSampleTopo_grid_failed topo_grid_failed.rb] - a ''topology'' with all the nodes that have failed during the "imaging" process (possibly due to some disk read/write errors)  
 * [wiki:Tutorial/HowToImageSampleTopo_grid_timedout topo_grid_timeoud.rb] - a ''topology'' with all the nodes that have timed out the "imaging" process. These nodes correctly started writing the image on their disk, but they did not finish before the default timeout of 800 sec.

You can either use the information in the ''topo_grid_active.rb'' file to select nodes for your experiments, OR directly use the topology defined in this file within your experiment scripts.