# mpi.conf

Section: Slurm Configuration File (5)
Updated: Slurm Configuration File
Index

## NAME

mpi.conf - Slurm configuration file to allow the configuration of MPI plugins.

## DESCRIPTION

mpi.conf is an ASCII file which defines parameters that control the behavior of MPI plugins. Currently the configuration file can only be used to configure the PMIx plugin, but it can be extended to support other MPI plugins as well. The file will always be located in the same directory as the slurm.conf. This file is optional.

Parameter names are case insensitive. Any text following a "#" in the configuration file is treated as a comment through the end of that line. Changes to the configuration file take effect upon restart of Slurm daemons, daemon receipt of the SIGHUP signal, or execution of the command "scontrol reconfigure" unless otherwise noted.

Settings from this configuration file can be viewed in the output of "scontrol show config". This configuration file can be included when using "configless" mode. Information from mpi.conf is read at startup or upon reconfigure by slurmctld and slurmd. Instances of slurmstepd for batch steps will receive information about the plugin requested from slurmd.

## PARAMETERS

PMIxCliTmpDirBase=<path>
  Directory to have PMIx use for temporary files. Defaults to not being set.

PMIxCollFence={mixed|tree|ring}
  Define the type of fence to use for collecting inter-node data. Defaults to not being set. See also PMIxFenceBarrier.

PMIxDebug={0|1}
  Enable debug logging for the PMIx plugin. Defaults to 0.

PMIxDirectConn={true|false}
  Disable direct launching of tasks. Default is "true".

PMIxDirectConnEarly={true|false}
  Allow early connections to a parent node. Defaults to "false".

PMIxDirectConnUCX={true|false}
  Allow PMIx to use UCX for communication. Defaults to "false".

PMIxDirectSameArch={true|false}
  Enable additional communication optimizations when PMIxDirectConn is set to true, assuming all the job's nodes have the same architecture. Defaults to "false".

PMIxEnv=<environment variables>
  Semicolon separated list of environment variables to be set in job environments to be used by PMIx. Defaults to not being set.

PMIxFenceBarrier={true|false}
  Define whether to fence inter-node communication for data collection. Default is "false". See also PMIxCollFence.

PMIxNetDevicesUCX=<device type>
  Type of network device to use for communication. This will set the UCX_NET_DEVICES environment variable in only the slurmstepd environment. Defaults to not being set.

PMIxShareServerTopology={true|false}
  Allow the PMIx server to share its copy of the local node topology of the job with clients. If set to true, the PMIx server will set any necessary key-value pairs in the job-level information provided to each client. The topology will not be shared via shared memory. Defaults to "false".

  NOTE: This is only supported by PMIx v4.x+.

PMIxTimeout=<time>
  The maximum time (in seconds) allowed for communication between hosts to take place. Defaults to 300 seconds.

PMIxTlsUCX=<tl1>[,<tl2>...]
  Sets the UCX_TLS variable, which restricts the transports to use, in the slurmstepd environment. The accepted values are defined in the UCX documentation and may vary between installations. Multiple values can be set and must be separated by commas. If not set, UCX tries to use all available transports and selects the best ones according to their performance capabilities and scale. Defaults to not being set.

## COPYING

Copyright (C) 2022 SchedMD LLC.

This file is part of Slurm, a resource management program. For details, see <https://slurm.schedmd.com/>.

Slurm is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

Slurm is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

## SEE ALSO

slurm.conf(5)

## Index

NAME
DESCRIPTION
PARAMETERS
COPYING
SEE ALSO

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Time: 13:59:11 GMT, February 22, 2026