Can't start daemon su when booting

[GeneBlue]

Hi:
It seems this su-binary can not be a daemon su when booting. I hijacked debuggerd like this：

#!/system/bin/sh

/system/xbin/daemonsu --daemon &
/system/xbin/supolicy --live
/system/xbin/supolicy --live "permissive zygote;"
/system/xbin/supolicy --live "permissive kernel;"
/system/xbin/supolicy --live "permissive init;"
/system/xbin/supolicy --live "permissive daemonsu;"
/system/xbin/supolicy --live "permissive init_shell;"
/system/xbin/supolicy --live "permissive shell;"
/system/xbin/supolicy --live "permissive servicemanager;"
/system/bin/debuggerd_real

when i reboot my phone, debuggerd_real will be running, but daemonsu not be a deamon.

another, my phone is nexus 5, android 5.0.1, LRX22C