ROS2 Humble on Windows - "failed to create process."

Question

I am trying to install ROS2 "Humble Hawksbill" on Windows 10, but when done and trying to run ros2 I get the error:

failed to create process.

I get the same result when activating the ROS environment first with local_setup.

I followed the instructions here: https://docs.ros.org/en/humble/Installation/Windows-Install-Binary.html#install-python
The only difference is I have Python 3.8.10. Other system info:

> systeminfo.exe

Host Name:                 xxxx
OS Name:                   Microsoft Windows 10 Pro
OS Version:                10.0.19045 N/A Build 19045
OS Manufacturer:           Microsoft Corporation
OS Configuration:          Member Workstation
OS Build Type:             Multiprocessor Free
Registered Owner:          sa-install
Registered Organization:   Demcon
Product ID:                00330-80000-00000-AA932
Original Install Date:     15-4-2022, 05:14:30
System Boot Time:          12-9-2023, 10:41:29
System Manufacturer:       HP
System Model:              HP ZBook Fury 15.6 inch G8 Mobile Workstation PC
System Type:               x64-based PC
Processor(s):              1 Processor(s) Installed.
                           [01]: Intel64 Family 6 Model 141 Stepping 1 GenuineIntel ~2304 Mhz
BIOS Version:              HP T95 Ver. 01.08.20, 14-3-2022
Windows Directory:         C:\windows
System Directory:          C:\windows\system32
Boot Device:               \Device\HarddiskVolume1
System Locale:             en-gb;English (United Kingdom)
Input Locale:              en-us;English (United States)
Time Zone:                 (UTC+01:00) Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna
Total Physical Memory:     16'048 MB
Available Physical Memory: 6'033 MB
Virtual Memory: Max Size:  28'336 MB
Virtual Memory: Available: 11'376 MB
Virtual Memory: In Use:    16'960 MB
Page File Location(s):     C:\pagefile.sys
Domain:                    xxxx
Logon Server:              xxxx
Hotfix(s):                 20 Hotfix(s) Installed.

There are some similar questions already, but their accepted answers did not help me:

• Ros2 Galactic binary installation on Windows 10: failed to create process
• failed to create ROS2 process

EDIT: I just realized that calling ROS2 from Python does work:

> python Scripts\ros2-script.py
usage: ros2 ...

But running the .exe gives the error:

> ros2.exe
failed to create process.

Answer 1

I think I more or less solved it. I redid my steps in Windows Sandbox, to test from a fresh system, and I found the following:

1. Download ROS2 binaries without anything else. Unpacked into C:\dev\ros2_humble
   • Running Scripts\ros2.exe now gives my infamous error "failed to create process."
   • local_setup.ps1 now fails of course, as no Python is available.
2. Install Python 3.8.3 with default settings, under C:\Program Files\Python38, without adding to path (to mimic my PC with multiple Python versions).
   • Same results in the previous step.
   • Running & "C:\Program Files\Python38\python.exe" Scripts\ros2-script.py gives errors about missing packages (of course).
3. Install requirements: & "C:\Program Files\Python38\python.exe -m pip install ...
   • & "C:\Program Files\Python38\python.exe" Scripts\ros2-script.py now seems to work fine, without errors!
   • ros2.exe still gives "failed to create process.". But that I could understand, Python isn't available yet.
4. Add system Python to PATH
   • python Scripts\ros2-script.py now also works
   • ros2.exe still fails with the same error

Then either:

1. Create a symbolic link: mklink /D "C:\Python38" "C:\Program Files\Python38"
   • Running ros2.exe now actually works! It seems it really relies on the hardcoded Python path.

or

1. Edit Scripts\ros2-script.py and replace the hash-bang path at the top C:\Python38\python.exe with C:\Program Files\Python38\python.exe
   • Running ros2.exe now also works! I had no idea the .exe was actually relying on the hash-bang path.

Finally I wanted to test with Python virtual environments. I rolled back to step #2 (with only Ros2 unpacked and a fresh Python install).

1. Create venv, in C:\dev\ros2_humble\: & "C:\Program Files\Python38\python.exe" -m venv .venv
2. Activate it: .\venv\Scripts\activate.ps1
3. Check it and prepare it: python --version and python -m pip install ...
4. Now also activate the ros2 environment: local_setup.ps1
   • python Scripts\ros2-script.py now works!
   • But ros2.exe still fails... It depends on the fixed paths.
5. Edit *-script.py such that the line 1 path says #!C:\dev\ros2_humble\.venv\Scripts\python.exe
   • And now finally ros2.exe just works, from an isolated environment!

So in a nutshell:

• The hash-bang path from *-script.py must match with the intended Python executable
• local_setup.ps1 but be active, i.e. PYTHONPATH must include the site-packages from ros2 and the interpreter library path (either system or a venv)

And the error

failed to create process.

was entirely due to the script hash-bang not being available.