====== Add an interface to a Rocks Cluster compute node ======

Right after installation the compute nodes have no access to the outside network/world.  This is of course problematic (especially if you have a licence server on the network).  There are two ways how to fix this.  First, either route traffic to the outside network via the frontend.  Good luck with that, I have tried everything twice with no success and asked the experts [[https://lists.sdsc.edu/pipermail/npaci-rocks-discussion/2015-August/067936.html|here]] and [[https://lists.sdsc.edu/pipermail/npaci-rocks-discussion/2015-August/067952.html|here]].  You have to love "//I'd simply start over on your frontend//".

The second way is to be lucky (or well-off) and have a second interface on each compute node which you can connect to the outside world (or switch).  Even so, this is not straightforward.  Note that the second interface of a rocks compute node is not installed by default.  In the below the interface is assumed to be prefixed with //em// (instead of //eth//), and we assume we are adding an interface on //compute-0-0//.  Apply your case accordingly.

As **root**:

  - Do a ''rocks list network'' and record the names of the networks (e.g. by default the public network will be called ''public'')
  - ''rocks list host interface'' will tell you which interfaces are installed on each compute/frontend.  //em1// will almost certainly be your private interface and link to the frontend.  Note that if //em2// is present but has no details (default install) you will need to delete this.
    - You can do this via ''rocks remove host interface compute-0-0 em2'' 
  - You will need to find the MAC of the compute node you want to install.  Log in the compute node and issue ''ifconfig -a''.  Note the MAC address.
  - To install the public interface run ''rocks add host interface compute-0-0 em2 ip=10.1.2.110 mac=F2:BB:CB:D3:1F:C4 subnet=public'' with the appropriate IP and MAC address.  Note that the //subnet// field specifies the network you want to connect to (found from Step 1 above).
  - Check that the installation worked ''rocks list host interface''
  - You now need to sync the network and cluster with the newly added interface (let Rocks know about it):
    - ''rocks sync config''
    - ''rocks sync host network''