improve this:  VantronOS users may look into the summaries below and choose either way that best suit their requirements for the custom development.
1. When developed using SDK, applications installed via ipk packages will lose after system settings restore of VantronOS, yet they will not lose when manually copied to the user partition of VantronOS.
2. When compiled by a crosss compilation toolchain, applications installed to the user partition of VantronOS as directed in this guide will not lose after system settings are restored.
Note: The compiling is supposed to be completed in a Linux environment, and Ubuntu18.04 64bit operating system is used in this guide.