私の使っているベアボーンPC（Ubuntu20.04）で
openFOAMのv2006にて下記のようなエラーが出ることがあります。
ログイン名はuserでcaseというフォルダ内で実行するとします。
user@user-desktop:~/OpenFOAM/user-v2006/run/case$ paraFoam
Invalid $PV_PLUGIN_PATH and -plugin-path= not defined
No supplementary ParaView/OpenFOAM reader modules
Using builtin reader: paraFoam -vtk
Created temporary 'case.foam'
--------------------------------------------------------------------------
No network interfaces were found for out-of-band communications. We require
at least one available network for out-of-band messaging.
--------------------------------------------------------------------------
[user-desktop:47917] [[INVALID],INVALID] ORTE_ERROR_LOG: Unable to start a daemon on the local node in file ess_singleton_module.c at line 716
[user-desktop:47917] [[INVALID],INVALID] ORTE_ERROR_LOG: Unable to start a daemon on the local node in file ess_singleton_module.c at line 172
--------------------------------------------------------------------------
It looks like orte_init failed for some reason; your parallel process is
likely to abort. There are many reasons that a parallel process can
fail during orte_init; some of which are due to configuration or
environment problems. This failure appears to be an internal failure;
here's some additional information (which may only be relevant to an
Open MPI developer):
orte_ess_init failed
--> Returned value Unable to start a daemon on the local node (-127) instead of ORTE_SUCCESS
--------------------------------------------------------------------------
--------------------------------------------------------------------------
It looks like MPI_INIT failed for some reason; your parallel process is
likely to abort. There are many reasons that a parallel process can
fail during MPI_INIT; some of which are due to configuration or environment
problems. This failure appears to be an internal failure; here's some
additional information (which may only be relevant to an Open MPI
developer):
ompi_mpi_init: ompi_rte_init failed
--> Returned "Unable to start a daemon on the local node" (-127) instead of "Success" (0)
--------------------------------------------------------------------------
*** An error occurred in MPI_Init
*** on a NULL communicator
*** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort,
*** and potentially your MPI job)
[user-desktop:47917] Local abort before MPI_INIT completed completed successfully, but am not able to aggregate error messages, and not able to guarantee that all other processes were killed!
色々インストールしているのと私のPC環境が原因かもしれませんが
対処方法としてはネットワーク（Wi-Fi）の接続を一回オフにしてからオンにすると
インターネットの回線が復活してなぜかparaFoamもできるようになります。
