# problem in md run

**URL:** <https://gromacs.bioexcel.eu/t/problem-in-md-run/8411>\
**Category:** User discussions\
**Created:** [February 23, 2024, 5:54pm UTC](https://gromacs.bioexcel.eu/t/problem-in-md-run/8411 "2024-02-23T17:54:43Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![samar](https://avatars.discourse-cdn.com/v4/letter/s/dfb087/32.png) [@samar](https://gromacs.bioexcel.eu/u/samar)\
**Post date:** [February 23, 2024, 5:54pm UTC](https://gromacs.bioexcel.eu/t/problem-in-md-run/8411/1 "2024-02-23T17:54:43Z")

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Error in user input:  
Invalid input values  
In option s  
Required option was not provided, and the default file ‘topol’ does not  
exist or is not accessible.  
The following extensions were tried to complete the file name:  
.tpr

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<div class="post-metadata">

**Author:** ![MagnusL](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/magnusl/32/2380_2.png) [@MagnusL](https://gromacs.bioexcel.eu/u/MagnusL)\
**Post date:** [February 24, 2024, 1:38pm UTC](https://gromacs.bioexcel.eu/t/problem-in-md-run/8411/2 "2024-02-24T13:38:54Z")

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You need a tpr input file, created by `gmx grompp`, to run `gmx mdrun`. The tpr file name is specified using the `-s` option.

Read [https://manual.gromacs.org/current/user-guide/getting-started.html](https://manual.gromacs.org/current/user-guide/getting-started.html) for more info.