Cannot properly load isaacsim.ros2.bridge extension from standalone script

ekliptiko · October 29, 2025, 11:48pm

Isaac Sim Version

5.1.0
5.0.0
4.5.0
4.2.0
4.1.0
4.0.0
4.5.0
2023.1.1
2023.1.0-hotfix.1
Other (please specify):

Operating System

Ubuntu 24.04
Ubuntu 22.04
Ubuntu 20.04
Windows 11
Windows 10
Other (please specify):

GPU Information

Model: L40s
Driver Version: 570.172.08

Topic Description

Cannot properly load isaacsim.ros2.bridge extension from a standalone script. I would relaly prefer to NOT have to set env vars in the terminal prior to launching the script, but I cannot get it to work regardless.

My setup:

AWS g6e.2xlarge
Nvidia IsaacSim AMI ( AWS Marketplace: NVIDIA Isaac Sim™ Development Workstation (Linux) )
Ubuntu 24.04
HUMBLE ros2 container (yes, humble.)

Detailed Description

I have tried:

source setup_ros_env.sh && ./python.sh workspace/mxi-isaacsim/main.py (without any setting of any env var in the python script)
This results in ROS_DISTRO=jazzy, and python crashes.
as another attempt: after running source setup_ros_env.sh, i tried export ROS_DISTRO=humble
results in the following:

[11.346s] [ext: isaacsim.ros2.bridge-4.9.3] startupFatal glibc error: malloc.c:2599 (sysmalloc): assertion failed: (old_top == initial_top (av) && old_size == 0) || ((unsigned long) (old_size) >= MINSIZE && prev_inuse (old_top) && ((unsigned long) old_end & (pagesize - 1)) == 0)2025-10-29T23:35:47Z [11,410ms] [Warning] [carb] Acquiring non optional plugin interface which is not listed as dependency: [carb::dictionary::ISerializer v1.1] (plugin: carb.dictionary.serializer-json.plugin), by client: carb.scenerenderer-rtx.plugin. Add it to CARB_PLUGIN_IMPL_DEPS() macro of a client.Aborted (core dumped)

[11.725s] To use the internal libraries included with the extension please set the following environment variables to use with FastDDS (default) or CycloneDDS before starting Isaac Sim:

FastDDS (default):export ROS_DISTRO=humbleexport RMW_IMPLEMENTATION=rmw_fastrtps_cppexport LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/IsaacSim/exts/isaacsim.ros2.bridge/humble/lib

OR

CycloneDDS:export ROS_DISTRO=humbleexport RMW_IMPLEMENTATION=rmw_cyclonedds_cppexport LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/IsaacSim/exts/isaacsim.ros2.bridge/humble/lib

2025-10-29T23:35:47Z [11,704ms] [Error] [isaacsim.ros2.bridge.impl.extension] ROS2 Bridge startup failed[11.883s] [ext: isaacsim.ros2.bridge-4.9.3] shutdown
setting ROS_DISTRO=humble, `RMW_IMPLEMENTATION=rmw_fastrtps_cpp` and LD_LIBRARY_PATHenv manually with export … before launching my python script

… WAY too many python crashes to copy here
using os.environ… inside the python script (before importing SimulationApp):
I still get the console warning from attempt 1).

The nuance is that I need humble, not jazzy, even though my host OS is ubuntu 24.04… And I know it CAN load humble just fine because it works great from isaac-sim.selector.sh

…so… how do we enable ros2 bridge purely and solely from a standalone python script?

# Set ROS2 environment variables - required for ROS2 bridge to load completely:
os.environ["ROS_DISTRO"] = "humble"
os.environ["RMW_IMPLEMENTATION"] = "rmw_fastrtps_cpp"
# Ensure ROS2 bridge native libs are found. check if /opt/IsaacSim/exts/isaacsim.ros2.bridge/humble/lib exists in $LD_LIBRARY_PATH
ros2_bridge_lib_path = "/opt/IsaacSim/exts/isaacsim.ros2.bridge/humble/lib/"
if "LD_LIBRARY_PATH" in os.environ:
    if ros2_bridge_lib_path not in os.environ["LD_LIBRARY_PATH"]:
        os.environ["LD_LIBRARY_PATH"] += f":{ros2_bridge_lib_path}"
else:
    os.environ["LD_LIBRARY_PATH"] = ros2_bridge_lib_path
print("LD_LIBRARY_PATH:", os.environ["LD_LIBRARY_PATH"])
from isaacsim.simulation_app import SimulationApp
# Launch Isaac Sim in GUI mode
simulation_app = SimulationApp({"headless": False,}, experience="apps/isaacsim.exp.full.kit")

from isaacsim.core.api import SimulationContext
from isaacsim.core.prims.impl.xform_prim import XFormPrim
from isaacsim.core.utils.extensions import enable_extension
from isaacsim.core.utils.stage import add_reference_to_stage
from omni import usd

# enable ROS2 bridge extension
enable_extension("isaacsim.ros2.bridge")

infox22oo · November 1, 2025, 6:49pm

If you can live with setting environment variables, here’s what works on Ubuntu 24.04 to start Isaac Sim in a way that supports ROS2 Humble:

export isaac_sim_package_path=$HOME/isaacsim_5.1

export ROS_DISTRO=humble

export RMW_IMPLEMENTATION=rmw_fastrtps_cpp

export FASTRTPS_DEFAULT_PROFILES_FILE=/home/yourusername/IsaacSim-ros_workspaces/humble_ws/fastdds.xml


export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$isaac_sim_package_path/exts/isaacsim.ros2.bridge/humble/lib

$isaac_sim_package_path/isaac-sim.sh

This works in Isaac Sim 5.0 or 5.1, just change the first line based on which version you installed and where exactly you installed it. (Note that you need to run the post install script from the folder where you installed it)

Also note that you need to put your own username in the place of yourusername. The ~ shortcut for home does not seem to work reliably, you have to spell it out as /home/user

The nuance is that I need humble, not jazzy, even though my host OS is ubuntu 24.04

I actually have the opposite issue, I can run ROS2 Humble on Ubuntu 24.04 just fine, but Jazzy doesn’t work for me. I posted separately about that.

ekliptiko · November 17, 2025, 10:16pm

Still cant figure this out.

I just tried this on windows but still doesnt work…

run setup_ros_env.bat (no output; as expected)
run my script ./python.bat workspace/mxi-isaacsim/main.py

I get the following:

[11.305s] [ext: isaacsim.ros2.bridge-4.12.4] startup
2025-11-17T22:09:33Z [11,255ms] [Warning] [isaacsim.ros2.bridge.impl.extension] Using ‘humble’ as default
[11.343s] Using backup internal ROS2 humble distro

[12.799s] To use the internal libraries included with the extension, please set the environment variables using one of the following methods before starting Isaac Sim:

Command Prompt (CMD):
set ROS_DISTRO=humble
set RMW_IMPLEMENTATION=rmw_fastrtps_cpp
set PATH=%PATH%;c:/users/ted/isaac-sim-standalone-5.1.0-windows-x86_64/exts/isaacsim.ros2.bridge/humble/lib

PowerShell:
$env:ROS_DISTRO = “humble”
$env:RMW_IMPLEMENTATION = “rmw_fastrtps_cpp”
$env:PATH = “$env:PATH;c:/users/ted/isaac-sim-standalone-5.1.0-windows-x86_64/exts/isaacsim.ros2.bridge/humble/lib”

2025-11-17T22:09:34Z [12,733ms] [Error] [isaacsim.ros2.bridge.impl.extension] ROS2 Bridge startup failed

I dont understand how to launch a standalone python script and use the IsaacSim Internal Ros2 libs?

VickNV · April 17, 2026, 3:00am

Hi @ekliptiko,

I investigated this and found the root cause. The issue is that LD_LIBRARY_PATH must be set before the Python process starts – setting os.environ["LD_LIBRARY_PATH"] inside your script is too late.

Why `os.environ` Doesn’t Work

The Linux dynamic linker (ld.so) reads LD_LIBRARY_PATH once at process startup and caches the library search paths. When the ROS2 bridge plugin calls dlopen() to load librosidl_runtime_c.so and friends, it uses the cached paths from when Python first launched – your os.environ update only affects child processes, not the current one.

This is a fundamental Linux behavior, not an Isaac Sim bug.

Solution 1: Wrapper Script (Simplest)

Create a launch.sh next to your script:

#!/bin/bash
SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
ISAAC_PATH="${ISAAC_SIM_PATH:-$HOME/isaacsim}"

export ROS_DISTRO=humble
export RMW_IMPLEMENTATION=rmw_fastrtps_cpp
export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:${ISAAC_PATH}/exts/isaacsim.ros2.bridge/humble/lib"

exec "${ISAAC_PATH}/python.sh" "$SCRIPT_DIR/main.py" "$@"

Then just run ./launch.sh instead of ./python.sh main.py.

Solution 2: Self-Re-Exec in Python (No Shell Script Needed)

Add this at the very top of your script, before any Isaac Sim imports:

import os, sys

def ensure_ros2_env(ros_distro="humble"):
    isaac_path = os.environ.get("ISAAC_SIM_PATH")
    if not isaac_path:
        for candidate in [os.path.expanduser("~/isaacsim"), "/opt/IsaacSim"]:
            if os.path.exists(os.path.join(candidate, "VERSION")):
                isaac_path = candidate
                break
    if not isaac_path:
        raise RuntimeError("Cannot find Isaac Sim. Set ISAAC_SIM_PATH.")

    ros2_lib = os.path.join(isaac_path, "exts", "isaacsim.ros2.bridge", ros_distro, "lib")
    current_ld = os.environ.get("LD_LIBRARY_PATH", "")

    if ros2_lib in current_ld:
        return  # Already set, continue normally

    # Re-exec with correct LD_LIBRARY_PATH
    env = os.environ.copy()
    env["ROS_DISTRO"] = ros_distro
    env["RMW_IMPLEMENTATION"] = env.get("RMW_IMPLEMENTATION", "rmw_fastrtps_cpp")
    env["LD_LIBRARY_PATH"] = f"{current_ld}:{ros2_lib}" if current_ld else ros2_lib
    os.execve(sys.executable, [sys.executable] + sys.argv, env)

ensure_ros2_env("humble")  # <-- re-execs if needed, then continues

# Now safe to import Isaac Sim
from isaacsim import SimulationApp
app = SimulationApp({"headless": False})

from isaacsim.core.utils.extensions import enable_extension
enable_extension("isaacsim.ros2.bridge")
# ... rest of your code

This works because os.execve() replaces the current process with a new one where LD_LIBRARY_PATH is set correctly from the start. I tested this on Isaac Sim 5.1.0 and the bridge loads successfully.

Note on Ubuntu 24.04 + Humble

Your setup (Ubuntu 24.04 wanting Humble instead of Jazzy) is supported – you just need to explicitly set ROS_DISTRO=humble since the auto-detection maps 24.04 to Jazzy. Both solutions above handle this.

For Windows

On Windows, the issue is different – PATH (not LD_LIBRARY_PATH) needs the ROS2 libs. The extension source code (ros2_common.py) already handles Windows PATH setup automatically during on_startup(), but only if ROS_DISTRO is set. Use os.environ["ROS_DISTRO"] = "humble" before SimulationApp() – this should work on Windows since DLL loading checks PATH dynamically (unlike Linux’s LD_LIBRARY_PATH). If it still fails, use the wrapper script approach with set PATH=%PATH%;... before launching Python.

VickNV · May 1, 2026, 3:25am

I’m closing this topic due to no response from the original poster for over two weeks.

If you are still experiencing this issue, please open a new topic and link back to this one.

For others hitting a similar problem, we recommend checking the ROS 2 bridge documentation for your Isaac Sim version and verifying your ROS_DISTRO, RMW_IMPLEMENTATION, and LD_LIBRARY_PATH are set as described there before launching your standalone script.

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