Hi Justin, You can disable cobalt by adding this to your Hydra/MPICH configure: --with-hydra-bss=user,ssh,rsh,fork,slurm,ll,lsf,sge,pbs,manual,persist This is basically the default setting minus cobalt. Ken On 04/27/2018 10:37 AM, Justin M Wozniak wrote:

Hi     I am trying to use an MPI program to manage an ensemble of apruns under Cobalt on Theta.  I compiled an MPICH 3.2 for the login node. Then, in an interactive allocation, I do:

$ hostname thetamom2

$ mpiexec -launcher fork -n 1 echo hi [mpiexec@thetamom2] HYDU_parse_hostfile (utils/args/args.c:319): unable to open host file: /var/tmp/cobalt.222331 [mpiexec@thetamom2] HYDT_bscd_cobalt_query_node_list (tools/bootstrap/external/cobalt_query_node_list.c:27): error parsing hostfile [mpiexec@thetamom2] HYDT_bsci_query_node_list (tools/bootstrap/src/bsci_query_node_list.c:19): RMK returned error while querying node list [mpiexec@thetamom2] main (ui/mpich/mpiexec.c:186): unable to query the RMK for a node list

It looks like Hydra has detected that it is under Cobalt.  How do I force it to ignore Cobalt?

Ultimately, I plan to replace 'echo' with a shell script that does an aprun.

    Thanks

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