@John-Smith-0 Take a look at this thread on setting up CMake for Docker and Omega, maybe it helps. https://community.onion.io/topic/1592/project-docker-omega2-sdk-for-cross-compilation-cmake-support/35 nosys.specs is used in a cross compiling environment where the host is not available such as when you are compiling on linux to deploy on OpenWrt. When openmodbus is being linked it seems it cannot find the required library stubs. You need to look to see what it is linking with, I don't use CMake nor OpenModbus so I cannot check.

@OSO-Bear my guess would be that you are using dynamic linking and have a version mismatch in your libraries. Try statically linking and if this is successfully take a look at the versions you are compiling and and running against.

@Jasvivek-Reehal In order to use those libraries in your C/C++ code you need to cross-compile your program first using our build system. Please refer to our guide on how to setup the build system, how to compile C programs and how to actually cross-compile programs. You will find all the necessary steps and description. Also, check out our documentation to learn more about Library for Linker. I hope this will help!