 For efficiency, most microkernels contain schedulers and manage timers, in violation of the minimality principle and the principle of policy-mechanism separation.Start up (booting) of a microkernel-based system requires device drivers, which are not part of the kernel.Typically this means that they are packaged with the kernel in the boot image, and the kernel supports a bootstrap protocol that defines how the drivers are located and started; this is the traditional bootstrap procedure of L4 microkernels.