[Facts] boot chain for UEFI and ZFS

posted in: computer | 0

boot -chain example with UEFI (=sucessor of BIOS):


UEFI the pc is powered on and the UEFI begins with self-test routines
(configured in UEFI)
UEFI boots from the configured device (e.g. “1st boot device = HDD”)

(sector 1-33)

 … UEFI reads the GPT of the device and the partition with the bootme-flag is further loaded
GPT-Partition 1

with bootme-flag

(part.-type: freebsd-boot)

(sector: e.g. 34-1058)

includes the zfs-bootloader (=gptzfsboot) and this loader searches for zpool’s with enabled bootfs-property (the first found zpool with this property is choosen)

(bootfs = zroot)

(part.-type: freebsd-zfs)

 the further boot continues from the zfs, which is set as bootfs (e.g. “zroot”)

(root filesystem with

FreeBSD installation)

the zfs-bootloader reads the zfs and loads the kernel


read configuration, load modules, initilialize devices (etc cetera)
init / rc.d
read configuration, configure devices, start daemons (etc cetera)



some useful commands:

#install the protected-mbr (=pmbr) into the first sector (=mbr) of the device /dev/ada0
gpart bootcode -b /boot/pmbr /dev/ada0

#install the zfs-bootloader (=gptzfsboot) into partition 1 of the device /dev/ada0
gpart bootcode -p /boot/gptzfsboot -i 1 /dev/ada0


if there are any errors in my explanations, please don’t hesitate to contact me.