109 lines
4.2 KiB
Markdown
109 lines
4.2 KiB
Markdown
---
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title: Known Problems
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#tags:
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#keywords:
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last_updated: 21 January 2021
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#summary: ""
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sidebar: merlin6_sidebar
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permalink: /merlin6/known-problems.html
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---
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## Known Problems Summary
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| Topic |
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|:----------------------------------------------------------------------------------------- |
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| [Default Shell](/merlin6/known-problems.html#default-shell) |
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| [OpenGL vs Mesa](/merlin6/known-problems.html#opengl-vs-mesa) |
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| [Paraview](/merlin6/known-problems.html#OpenGL) |
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| [ANSYS](/merlin6/known-problems.html#opengl-support-paraview-ansys-etc) |
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| [Illegal instructions error](i/merlin6/known-problems.html#illegal-instructions) |
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## Default SHELL
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In general, **`/bin/bash` is the recommended default user's SHELL** when working in Merlin.
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Some users might notice that BASH is not the default SHELL when login to Merlin systems, or they might need to run a different SHELL.
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This is probably because when the PSI account was requested, no SHELL description was specified or a different one was requested explicitly by the requestor.
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Users can check which is the default SHELL specified in the PSI account with the following command:
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```bash
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getent passwd $USER | awk -F: '{print $NF}'
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```
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If SHELL does not correspond to the one you need to use, you should request a central change for it.
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This is because Merlin accounts are central PSI accounts. Hence, **change must be requested via [PSI Service Now](/merlin6/contact.html#psi-service-now)**.
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Alternatively, if you work on other PSI Linux systems but for Merlin you need a different SHELL type, a temporary change can be performed during login startup.
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You can update one of the following files:
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* `~/.login`
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* `~/.profile`
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* Any `rc` or `profile` file in your home directory (i.e. `.cshrc`, `.bashrc`, `.bash_profile`, etc.)
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with the following lines:
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```bash
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# Replace MY_SHELL with the bash type you need
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MY_SHELL=/bin/bash
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exec $MY_SHELL -l
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```
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Notice that available *shells* can be found in the following file:
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```bash
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cat /etc/shells
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```
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## OpenGL vs Mesa
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Some applications can run with OpenGL support. This is only possible when the node contains a GPU card.
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In general, X11 with Mesa Driver is the recommended method as it will work in all cases (no need of GPUs). In example, for ParaView:
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```bash
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module load paraview
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paraview-mesa paraview # 'paraview --mesa' for old releases
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```
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However, if one needs to run with OpenGL support, this is still possible by running `vglrun`. Officially, the supported method is
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NoMachine remote desktop (SSH with X11 Forwarding is slow, but also needs to properly setup the client -desktop or laptop-, where
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Merlin admins have no access or rights to it). In example, for running Paraview:
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```bash
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module load paraview
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vglrun paraview
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```
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## ANSYS
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Sometimes, running ANSYS/Fluent requires X11 support. For that, one should run fluent as follows.
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```bash
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module load ANSYS
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fluent -driver x11
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```
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## Paraview
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For running Paraview, one can run it with Mesa support or OpenGL support.
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```bash
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module load paraview
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# Run with Mesa support (nodes without GPU)
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paraview-mesa paraview # 'paraview --mesa' for old releases
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# Run with OpenGL support (nodes with GPU)
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vglrun paraview
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```
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## Illegal instructions
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It may happened that your code, compiled on one machine will not be executed on another throwing exception like **"(Illegal instruction)"**.
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This is usually because the software was compiled with a set of instructions newer than the ones available in the node where the software runs,
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and it mostly depends on the processor generation.
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In example, `merlin-l-001` and `merlin-l-002` contain a newer generation of processors than the old GPUs nodes, or than the Merlin5 cluster.
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Hence, unless one compiles the software with compatibility with set of instructions from older processors, it will not run on old nodes.
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Sometimes, this is properly set by default at the compilation time, but sometimes is not.
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For GCC, please refer to https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html for compiling options. In case of doubts, contact us.
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