Skip site navigation (1)Skip section navigation (2)

FreeBSD Man Pages

Man Page or Keyword Search:
Man Architecture
Apropos Keyword Search (all sections) Output format
home | help
GEOM_MAP(4)	       FreeBSD Kernel Interfaces Manual		   GEOM_MAP(4)

     geom_map -- GEOM module that maps defined items as	separate partitions

     To	compile	this driver into the kernel, place the following line in your
     kernel configuration file:

	   device geom_map

     The geom_map framework provides support for mapping defined parts of the
     media.  Basically it is helpful for embedded devices where	in the one
     continuous	flash are loader, kernel and rootfs parts.  geom_map allows
     making them available as separate parts and protects the loader from
     being overwritten.

     At	boot time geom_map partitions are listed (only with bootverbose) as:

	   MAP:	0x30000, data=0x30000 "/dev/map/bootloader"
	   MAP:	30000x10000, data=0x10000 "/dev/map/factory"
	   MAP:	40000x7a0000, data=0x7a0000 "/dev/map/upgrade"
	   MAP:	search key ".!/bin/sh" from 0x100000, step 0x10000
	   MAP:	40000x110000, data=0x110000 "/dev/map/kernel"
	   MAP:	search key ".!/bin/sh" from 0x100000, step 0x10000
	   MAP:	150000x690000, data=0x690000 "/dev/map/rootfs"
	   MAP:	7e0000x20000, data=0x20000 "/dev/map/config"

     The current geom_map configuration	can be accessed	with the following
     sysctl(8) nodes: kern.geom.conftxt, kern.geom.confxml, and
     kern.geom.confdot or by using ``geom map list''.

	   # sysctl -n kern.geom.conftxt
	   0 MD	md0 10485760 512 u 0 s 512 f 0 fs 0 l 10485760 t malloc
	   0 DISK cfid0	8388608	4 hd 0 sc 0
	   1 MAP map/config 131072 4 i 5 o 8257536 entry 0 dsize 131072
	   1 MAP map/rootfs 6881280 4 i	4 o 1376256 entry 0 dsize 6881280
	   2 UNCOMPRESS	map/rootfs.uncompress 18677760 512
	   1 MAP map/kernel 1114112 4 i	3 o 262144 entry 0 dsize 1114112
	   1 MAP map/upgrade 7995392 4 i 2 o 262144 entry 0 dsize 7995392
	   1 MAP map/factory 65536 4 i 1 o 196608 entry	0 dsize	65536
	   1 MAP map/bootloader	196608 4 i 0 o 0 entry 0 dsize 196608

     Driver configuration can be done in device.hints(5).  List	of used	param-

     at	     select media to attach

     name    name of partition (will create device /dev/map/that_name)

     start   offset from the beginning of the parent media to start of the
	     mapped partition.	This field can also have a special value
	     "search:searchstart:searchstep:searchkey",	where:

		     offset from the beginning of the parent media where
		     search will be started

		     value of the increment used while searching for the par-
		     tition boundary markers

		     key which will be used to find partition boundary mark-
		     ers.  The wildcard	`.' can	be used	to match any character
		     on	that position

     end     offset from the beginning of the parent media to the end of the
	     mapped partition.	This field can also have the special value
	     "search:searchstart:searchstep:searchkey",	as described above.

     offset  offset where the data of the mapped partition begins

     Each record contains the start address (in	bytes) from the	media begin,
     size (in bytes), offset where the data of mapped partition	begins,	and
     the name of new device.

	   MAP:	150000x690000, data=0x690000 "/dev/map/rootfs"

     00150000 -	start address
     00690000 -	size
     00000000 -	data begin from	zero offset
     00690000 -	data size
     "map/rootfs" - new	media will be accessible via /dev/map/rootfs dev.

     If	we need	to implement layout shown above, we need to define the follow-
     ing hints:"cfid0""bootloader"

     This defines /dev/map/bootloader at disk cfid0 starting at	0x00000000 and
     ending at 0x00030000, it is also marked as	readonly."cfid0""factory""cfid0""upgrade""cfid0""kernel""search:0x00100000:0x10000:.!/bin/sh"

     This defines /dev/map/kernel at disk cfid0	starting at 0x00040000,	but
     the end position must be searched by finding the key ``.!/bin/sh'', from
     offset 0x00100000 to the end of media with	step 0x10000.  The real	marker
     in	this case is ``#!/bin/sh'', but	`#' terminates the line	when the hints
     file is parsed, so	we need	to use wildcard	`.' instead of `#'."cfid0""rootfs""search:0x00100000:0x10000:.!/bin/sh""cfid0""config"

     geom(4), geom(8), sysctl(8)

     The geom_map driver was written by	Aleksandr Rybalko <>.

FreeBSD	9.2			 May 17, 2011			   FreeBSD 9.2


Want to link to this manual page? Use this URL:

home | help