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GPTZFSBOOT(8)		    System Manager's Manual		 GPTZFSBOOT(8)

NAME
       gptzfsboot -- GPT bootcode for ZFS on BIOS-based	computers

DESCRIPTION
       gptzfsboot is used on BIOS-based	computers to boot from a filesystem in
       a  ZFS  pool.  gptzfsboot is installed in a freebsd-boot	partition of a
       GPT-partitioned disk with gpart(8).

IMPLEMENTATION NOTES
       The GPT standard	allows a variable number of partitions,	but gptzfsboot
       only boots from tables with 128 partitions or less.

BOOTING
       gptzfsboot tries	to find	all ZFS	pools that are composed	of  BIOS-visi-
       ble  hard disks or partitions on	them.  gptzfsboot looks	for ZFS	device
       labels on all visible disks and in discovered supported partitions  for
       all  supported partition	scheme types.  The search starts with the disk
       from which gptzfsboot itself was	loaded.	 Other	disks  are  probed  in
       BIOS  defined  order.  After a disk is probed and gptzfsboot determines
       that the	whole disk is not a ZFS	pool member, the individual partitions
       are probed in their partition table order.  Currently GPT and MBR  par-
       tition  schemes are supported.  With the	GPT scheme, only partitions of
       type freebsd-zfs	are probed.  The first pool  seen  during  probing  is
       used as a default boot pool.

       The  filesystem specified by the	bootfs property	of the pool is used as
       a default boot filesystem.  If the bootfs property is not set, then the
       root filesystem of the pool is  used  as	 the  default.	 loader(8)  is
       loaded  from  the  boot filesystem.  If /boot.config or /boot/config is
       present in the boot filesystem, boot options are	read from  it  in  the
       same way	as boot(8).

       The ZFS GUIDs of	the first successfully probed device and the first de-
       tected	 pool	 are	made	available    to	  loader(8)   in   the
       vfs.zfs.boot.primary_vdev and vfs.zfs.boot.primary_pool variables.

USAGE
       Normally	gptzfsboot will	boot in	fully automatic	mode.	However,  like
       boot(8),	it is possible to interrupt the	automatic boot process and in-
       teract  with  gptzfsboot	 through a prompt.  gptzfsboot accepts all the
       options that boot(8) supports.

       The filesystem specification and	the path to  loader(8)	are  different
       from boot(8).  The format is

       [zfs:pool/filesystem:][/path/to/loader]

       Both  the  filesystem and the path can be specified.  If	only a path is
       specified, then the default filesystem is used.	If  only  a  pool  and
       filesystem are specified, then /boot/loader is used as a	path.

       Additionally, the status	command	can be used to query information about
       discovered pools.  The output format is similar to that of zpool	status
       (see zpool(8)).

       The  configured	or  automatically  determined  ZFS  boot filesystem is
       stored in the loader(8) loaddev variable, and also set as  the  initial
       value of	the currdev variable.

FILES
       /boot/gptzfsboot	 boot code binary
       /boot.config	 parameters for	the boot block (optional)
       /boot/config	 alternative parameters	for the	boot block (optional)

EXAMPLES
       gptzfsboot  is  typically  installed  in	combination with a "protective
       MBR" (see gpart(8)).  To	install	gptzfsboot on the ada0 drive:

	     gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada0

       gptzfsboot can also be installed	without	the PMBR:

	     gpart bootcode -p /boot/gptzfsboot	-i 1 ada0

SEE ALSO
       boot.config(5), boot(8),	gpart(8), loader(8), zpool(8)

HISTORY
       gptzfsboot appeared in FreeBSD 7.3.

AUTHORS
       This manual page	was written by Andriy Gapon <avg@FreeBSD.org>.

BUGS
       gptzfsboot looks	for ZFS	meta-data only in  MBR	partitions  (known  on
       FreeBSD	as slices).  It	does not look into BSD disklabel(8) partitions
       that are	traditionally called partitions.   If  a  disklabel  partition
       happens	to  be	placed so that ZFS meta-data can be found at the fixed
       offsets relative	to a slice, then gptzfsboot will recognize the	parti-
       tion as a part of a ZFS pool, but this is not guaranteed	to happen.

FreeBSD	13.2		      September	15, 2014		 GPTZFSBOOT(8)

NAME | DESCRIPTION | IMPLEMENTATION NOTES | BOOTING | USAGE | FILES | EXAMPLES | SEE ALSO | HISTORY | AUTHORS | BUGS

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