[yocto] Busybox shell script misbehavior when it is launched by systemd service

[JH]

Hi,

I have a shell script myscript_launch.sh launched by systemd service,
in the shell script, it call another shell script in background:

if [ -f ${CHECK_ACTIVE} ]; then
    echo "script is already running" >> /tmp/debug.log
else
    /usr/bin/myscript_check_resource.sh &
    echo "launch script result: $?" >> /tmp/debug.log
fi

The script myscript_launch.sh had no problem to be launched by systemd
service, but it could not run another script in the background (no
problem if it launched another script not using "&". I could see
launch script result: 0 in the debug.log, there was no error, but I
could never see that that script myscript_check_resource.sh running.

If I run the script myscript_launch.sh from the debug terminal, I can
see the  "/usr/bin/myscript_check_resource.sh &" was running fine.

That is weird busybox behavior, anyone knows how to fix it?

Thank you.

Kind regards,

- jh