# Gmx pdb2gmx not working

**URL:** <https://gromacs.bioexcel.eu/t/gmx-pdb2gmx-not-working/1040>\
**Category:** User discussions\
**Created:** [November 3, 2020, 12:02am UTC](https://gromacs.bioexcel.eu/t/gmx-pdb2gmx-not-working/1040 "2020-11-03T00:02:52Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![sam](https://avatars.discourse-cdn.com/v4/letter/s/5f9b8f/32.png) [@sam](https://gromacs.bioexcel.eu/u/sam)\
**Post date:** [November 3, 2020, 12:02am UTC](https://gromacs.bioexcel.eu/t/gmx-pdb2gmx-not-working/1040/1 "2020-11-03T00:02:52Z")

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GROMACS version:2020.4

first i’m sorry for asking many questions but i’m stuck in installtion and cannot move to work beacuse of it … i’m trying to test gromacs working or not by using

> gmx pdb2gmx

but got

> Required option was not provided, and the default file ‘protein’ does not  
> exist or is not accessible.  
> The following extensions were tried to complete the file name:  
> .gro, .g96, .pdb, .brk, .ent, .esp, .tpr

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**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\
**Post date:** [November 3, 2020, 3:11am UTC](https://gromacs.bioexcel.eu/t/gmx-pdb2gmx-not-working/1040/2 "2020-11-03T03:11:09Z")

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If you try to invoke `pdb2gmx`, it requires real arguments. If you want to test your installation, work through a real tutorial.

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<div class="post-metadata">

**Author:** ![sam](https://avatars.discourse-cdn.com/v4/letter/s/5f9b8f/32.png) [@sam](https://gromacs.bioexcel.eu/u/sam)\
**Post date:** [November 3, 2020, 3:44am UTC](https://gromacs.bioexcel.eu/t/gmx-pdb2gmx-not-working/1040/3 "2020-11-03T03:44:06Z")

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Thanks for replyig , i will search but execuse me if you please can you help in this

> [@Nonbonded interactions on the GPU](https://gromacs.bioexcel.eu/t/nonbonded-interactions-on-the-gpu/1033/2):
>
> Hello, the error message indicates that Gromacs was not built with GPU support. Did you compile it yourself and specify -DGMX\_GPU=on when running cmake (as per the [installation guide](http://manual.gromacs.org/current/install-guide/index.html)), or get it from the Ubuntu repositories? If the latter, try compiling it yourself. Regards, Petter

the command is running well without gpu and i want to enforce gpu but facing problem