I submitted a job that changed the memory mode. After the reboot the job script started but my mpirun command failed with: [[email protected]] HYDU_parse_hostfile (../../utils/args/args.c:535): unable to open host file: /var/tmp/cobalt.152 [[email protected]] mfile_fn (../../ui/mpich/utils.c:450): error parsing hostfile [[email protected]] match_arg (../../utils/args/args.c:243): match handler returned error [[email protected]] HYDU_parse_array (../../utils/args/args.c:269): argument matching returned error [[email protected]] parse_args (../../ui/mpich/utils.c:4498): error parsing input array [[email protected]] HYD_uii_mpx_get_parameters (../../ui/mpich/utils.c:4819): unable to parse user arguments [[email protected]] HYDU_parse_hostfile (../../utils/args/args.c:535): unable to open host file: /var/tmp/cobalt.152 [[email protected]] mfile_fn (../../ui/mpich/utils.c:450): error parsing hostfile [[email protected]] match_arg (../../utils/args/args.c:243): match handler returned error [[email protected]] HYDU_parse_array (../../utils/args/args.c:269): argument matching returned error [[email protected]] parse_args (../../ui/mpich/utils.c:4498): error parsing input array [[email protected]] HYD_uii_mpx_get_parameters (../../ui/mpich/utils.c:4819): unable to parse user arguments Then I tried to start an interactive job (without specifying any memory mode) and I got the same nodes (knl04,05) and there is no node file: [jlselogin1 he4] qsub -n 2 -q knl_7210 -t 60 -I Wait for job 154 to start... Opening interactive session to knl04 Last login: Tue Aug 9 16:24:36 2016 from jlselogin1.ftm.alcf.anl.gov DISPLAY = 10.17.6.108:10.0 connected to knl04 ssh connection, ssh display would be:, 10.17.6.11:0.0 [knl04 ~] echo $COBALT_NODEFILE [knl04 ~] Steve -- Steven C. Pieper, Senior Physicist Emeritus: [email protected] Argonne National Laboratory, Physics Division, Bldg. 203, Argonne, IL 60439 Phone: 630-252-4232 Fax -6008 Secretary, Debra Beres, -4100 http://www.phy.anl.gov/theory/staff/scp.html