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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:

           options 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 UZIP map/rootfs.uzip 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

     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
                     partition boundary markers

                     key which will be used to find partition boundary
                     markers.  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
     following hints:


     This defines /dev/map/bootloader at disk cfid0 starting at 0x00000000 and
     ending at 0x00030000, it is also marked as readonly.




     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 `#'.



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

     The geom_map driver was written by Aleksandr Rybalko <[email protected]>.

FreeBSD 11.1-RELEASE-p4          June 8, 2015          FreeBSD 11.1-RELEASE-p4
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