How to run data conversion (convert_data_format_mj.py) in headless Ubuntu 22.04 (GLFW / mujoco.viewer issue)

[Zhan-BHU]

Hi, thanks for the great work on Holosoma.

I am trying to run the demo data conversion pipeline on a headless Ubuntu 22.04 server (no X11 / no DISPLAY), and I ran into an issue related to mujoco.viewer / GLFW initialization.

Issue

When running the demo data conversion script (e.g. convert_data_format_mj.py), the following error occurs:
GLFWError: (65550) b'X11: The DISPLAY environment variable is missing'
ERROR: could not initialize GLFW

From inspection, the error is triggered by the use of:

import mujoco.viewer as mjv
viewer = mjv.launch_passive(...)

Since mujoco.viewer relies on GLFW, this fails on a headless machine even though no visualization is actually required for data conversion.

Is there a recommended way to run data conversion in headless mode?
Is it expected that demo data conversion requires a GUI?
Is there an official headless / no-viewer option?
Would it be acceptable to skip mujoco.viewer entirely and run MuJoCo forward passes without launching a viewer?
Any guidance on the intended workflow for headless servers would be greatly appreciated.
Thanks!