# How to avoid passwordless ssh

**URL:** <https://community.openpbs.org/t/how-to-avoid-passwordless-ssh/2211>\
**Category:** Users/Site Administrators\
**Created:** [July 21, 2020, 9:00am UTC](https://community.openpbs.org/t/how-to-avoid-passwordless-ssh/2211 "2020-07-21T09:00:47Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![adarsh](https://avatars.discourse-cdn.com/v4/letter/a/f07891/32.png) [@adarsh](https://community.openpbs.org/u/adarsh)\
**Post date:** [July 21, 2020, 9:06pm UTC](https://community.openpbs.org/t/how-to-avoid-passwordless-ssh/2211/2 "2020-07-21T21:06:34Z")

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1. Yes please enable passwordless-SSH access for all the users of the system, with stricthost-key checking disabled or a way that suppresses this.

2. Please compile openmpi with PBS Pro TM API , please follow the discussion here  
[Openmpi support - #5 by adarsh](https://community.openpbs.org/t/openmpi-support/1396/5)

3. $usecp is used for stage in and stageout using cp command when locations are common to PBS Server and Compute Nodes

> [@kaox10](#):
>
> (I found this in [6.2 NFS and Other Networked Filesystems](http://docs.adaptivecomputing.com/torque/3-0-5/6.2filesystems.php))

Just to be sure and to clarify: openpbs and torque are not the same. Please follow this link [PBS Default number of nodes and number of cpus - #4 by scott](https://community.openpbs.org/t/pbs-default-number-of-nodes-and-number-of-cpus/834/4)

> [@kaox10](#):
>
> I have checked that one-node job works well.  
> Is this due to the ssh authentication?

By default if there is no tight integration between PBS Pro and OpenMPI then ssh or rsh launchers will be used [FAQ: Running MPI jobs](https://www.open-mpi.org/faq/?category=running#pls-rsh-agent) . If you have tight integration between PBS Pro and OpenMPI then pbs\_tmrsh would be used transparently with full control on the spawned processes with accounting and process cleaning

Please check this guide: [https://www.altair.com/pdfs/pbsworks/PBSAdminGuide19.2.3.pdf](https://www.altair.com/pdfs/pbsworks/PBSAdminGuide19.2.3.pdf) and go through the below sections:

1. 10.14 How Processes are Started Using MPI and PBS
2. 10.13.3.1 Compiling LAM MPI 7.x/Open MPI with the TM Module

Note:

1. Static IP addresses / hostname / DNS (forward/reverse resolvable) - /etc/hosts populated on all the nodes with all the systems of the cluster (do not use DHCP).
2. SELinux disabled (if disabled now , then system should be rebooted)
3. passwordless-ssh for all the users
4. Same UID and GID for all the users
5. ports 15001 to 15009 and 17001 open between PBS server/compute nodes and between the nodes

Hope this helps

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