To allow embedded operating systems to update their components on-the-fly, dynamic update mechanism is required for operating systems to be patched or added extra functionalities in without the need of rebooting the machines. However, embedded environments are usually resource-limited in terms of memory size, processing power, power consumption, and network bandwidth. Thus, dynamic update for embedded operating systems should be designed to make the best use of limited resources. In this paper, a server-side pre-linking mechanism is proposed to make dynamic updates of embedded operating system efficiently. Applying this mechanism can reduce not only memory usage and CPU processing time for dynamic update, but also data transmission size for updated components. Power consumption can be reduced as well. We have implemented this mechanism in LyraOS which is a component-based embedded operating system. Performance evaluation shows that the size of updated components applying the proposed dynamic update mechanism can be 65-86% smaller than applying the approach of Linux loadable kernel modules. Especially, the overheads in embedded clients are minimal since the component linking time in embedded clients is eliminated.