# Gromacs mpi run command

**URL:** <https://gromacs.bioexcel.eu/t/gromacs-mpi-run-command/12955>\
**Category:** User discussions\
**Created:** [November 20, 2025, 6:24am UTC](https://gromacs.bioexcel.eu/t/gromacs-mpi-run-command/12955 "2025-11-20T06:24:12Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![gq0067](https://avatars.discourse-cdn.com/v4/letter/g/5e9695/32.png) [@gq0067](https://gromacs.bioexcel.eu/u/gq0067)\
**Post date:** [November 20, 2025, 6:24am UTC](https://gromacs.bioexcel.eu/t/gromacs-mpi-run-command/12955/1 "2025-11-20T06:24:12Z")

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GROMACS version:2022.3

I am trying to continue my simulation on an HPC cluster using `gmx_mpi mdrun` with `-cpi` and `-append`.  
However, when I use the restart command, I get an error .

Here is the command I used:

srun --mpi=pmix\_v3 -n 16 gmx\_mpi mdrun  
-s /nlsasfs/home/biomol/alifaz/bn\_rep1\_full.tpr  
-deffnm bt\_rep1\_full  
-cpi bt\_rep1\_full.cpt  
-append  
-nsteps 428733500  
-v -ntomp 16

I want to confirm if this is the correct way to restart the simulation.  
Could you please tell me:

1. Is the command written correctly for continuing a run?

2. Do I need both `-cpi` **and** `-append`, or only one of them?

3. Is adding `-nsteps` in a continuation run correct?

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<div class="post-metadata">

**Author:** ![obZehn](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/obzehn/32/2629_2.png) [@obZehn](https://gromacs.bioexcel.eu/u/obZehn)\
**Post date:** [November 20, 2025, 9:27am UTC](https://gromacs.bioexcel.eu/t/gromacs-mpi-run-command/12955/2 "2025-11-20T09:27:44Z")

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Hi @gq0067

So

- `-append` should be automatic, you can re-enforce it, but you do not need it;
- `-cpi` is mandatory if you want to continue from a checkpoint file without recompiling a tpr file;
- the `-nsteps` should overwrite the number of steps inside the tpr file, so these shouldn’t cause any problems but just force your simulation to go on up to when the number of steps is reached (or the simulation stops beforehand).

The command seems overall fine. How is it failing? Can you post the error?