Embedded system firmware security reinforcement method and device and medium

The invention discloses an embedded system firmware security reinforcement method and device and a medium, and the method comprises the following steps: cutting and simplifying built-in software and directories related to a target demand in an original root file system, and generating a minimized bottom-layer file system; carrying out partition division based on the residual space of the original root file system, and creating a read-only intermediate-layer file system and a writable self-defined-layer file system; identifying an operation dependency directory of the original root file system, and copying a directory needing to be modified from the original root file system in combination with a target demand; after the system is restarted, a middle-layer file system and a user-defined-layer file system are mounted on the basis of OverlayFS file system service, and a multi-layer combined file system is formed; and carrying out related test and verification. According to the method, a multi-level joint file sy