From: Norman Geist (
Date: Wed Aug 05 2015 - 00:12:33 CDT



you need to make sure to not use more than half of the available memory with VMD when using external binaries, cause they are run from a TCL terminal via “exec”. The program call by exec is forked to protect the calling process, which causes a duplication of the original caller process, so requires the doubled memory to be reserved. This is where it fails.


There are two options to solve the problem.


1. Use less memory, e.g. less frames or exclude water from trajectory.

2. Use tachyon “internal”. This might still cause the same error on the final video generation. So you’d need to deselect the “delete image files” from the movie maker and run ffmpeg/ppmtompeg later on the image files manually.


Good luck


Norman Geist.


From: [] On Behalf Of Kshatresh Dutta Dubey
Sent: Wednesday, August 05, 2015 12:01 AM
Subject: vmd-l: VMD movie error


Dear Users,

I am using VMD 1.9.2 on a centos 6, 32 GB RAM, 2TB disk space, Nvidia GTX 680, machine. While saving my MD trajectories (350 ns, file size ~ 15 GB) as movie (Tachyon optix) , every time I am getting error " couldn't fork child process: not enough memory". I have attached the log file for VMD. I will appreciate if someone could help me to fix the problem.

Thanks in advance.

With best regards
Kshatresh Dutta Dubey
Post Doctoral Researcher,
Lise Meitner Center for Computational Quantum Chemistry
Hebrew University of Jerusalem Israel
Jerusalem, Israel