# Gmx hbond - can't obtain X PixMap compatible matrix file

**URL:** https://gromacs.bioexcel.eu/t/gmx-hbond-cant-obtain-x-pixmap-compatible-matrix-file/1368
**Category:** User discussions
**Created:** [January 1, 2021, 5:39pm UTC](https://gromacs.bioexcel.eu/t/gmx-hbond-cant-obtain-x-pixmap-compatible-matrix-file/1368 "2021-01-01T17:39:11Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![JakubH](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@JakubH](https://gromacs.bioexcel.eu/u/JakubH)
#### Post date: [January 1, 2021, 5:39pm UTC](https://gromacs.bioexcel.eu/t/gmx-hbond-cant-obtain-x-pixmap-compatible-matrix-file/1368/1 "2021-01-01T17:39:11Z")

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GROMACS version: 2018.4  
GROMACS modification: No  
Here post your question

When I write: gmx hbond -f eq3\_900\_1000.xtc -s eq3.tpr -hbn eq3\_dgdg\_5001.ndx -r 0.325 -b 905000 -e 905000

I get this error.  
Fatal error:  
Won’t make more than 99 backups of hbnum.xvg for you.  
The env.var. GMX\_MAXBACKUP controls this maximum, -1 disables backups.

For more information and tips for troubleshooting, please check the GROMACS  
website at [Errors - Gromacs](http://www.gromacs.org/Documentation/Errors)  
I want to obtain existence matrix for all hydrogen bonds over all frames. I will work on this data later to check something, but I am not able to get this data. Could you help me?

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### Author: ![alevilla](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/alevilla/32/439_2.png) [@alevilla](https://gromacs.bioexcel.eu/u/alevilla)
#### Post date: [January 4, 2021, 9:45am UTC](https://gromacs.bioexcel.eu/t/gmx-hbond-cant-obtain-x-pixmap-compatible-matrix-file/1368/2 "2021-01-04T09:45:03Z")

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Hi,  
gmx tools creates a back-up of the previous outputs everytime you run it in the same directory. These files are labelled as #…# and an increasing number (in your case #hbnum.xvg.1#). You hit the maximum of back-up file. You can systematically remove the files from the working directory or disable backups by setting environment variable  
“GMX\_MAXBACKUP = -1”

see [Environment Variables — GROMACS 2020.4 documentation](https://manual.gromacs.org/current/user-guide/environment-variables.html?highlight=disable%20backup)

Best regards  
Alessandra