The Landlock wrapper re-executes the greywall binary inside the sandbox with --landlock-apply. When greywall is run from a path outside the CWD (e.g., ~/bin/greywall from /home/user/project), the binary doesn't exist inside the sandbox because only system paths and CWD are mounted. This adds a --ro-bind for the greywall executable so the wrapper always works regardless of where the binary is located.