geom_map(4) manual page

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 parameters:

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:

searchstart

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

searchstep

value of the increment used while searching for the partition boundary markers

searchkey

key which will be used to find partition boundary markers. The wildcard ‘.amp;’ 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.

“	Unix is the answer, but only if you phrase the question very carefully.	”
— Belinda Asbell

Manual Pages — GEOM_MAP

NAME

CONTENTS

SYNOPSIS

DESCRIPTION

EXAMPLES

SEE ALSO

AUTHORS

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:
searchstart
	offset from the beginning of the parent media where search will be started
searchstep
	value of the increment used while searching for the partition boundary markers
searchkey
	key which will be used to find partition boundary markers. The wildcard ‘`.amp;`’ 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