diff options
| -rw-r--r-- | sbin/geom/class/part/gpart.8 | 102 |
1 files changed, 90 insertions, 12 deletions
diff --git a/sbin/geom/class/part/gpart.8 b/sbin/geom/class/part/gpart.8 index 4365d6b..d75ac9e 100644 --- a/sbin/geom/class/part/gpart.8 +++ b/sbin/geom/class/part/gpart.8 @@ -24,7 +24,7 @@ .\" .\" $FreeBSD$ .\" -.Dd June 6, 2011 +.Dd August 19, 2011 .Dt GPART 8 .Os .Sh NAME @@ -260,29 +260,21 @@ and .Fl i Ar index ) . Not all partitioning schemes have embedded bootstrap code, so the .Fl b Ar bootcode -option is scheme-specific in nature. -For the GPT scheme, embedded bootstrap code is supported. -The bootstrap code is embedded in the protective MBR rather than the GPT. +option is scheme-specific in nature (see the section entitled +.Sx BOOTSTRAPPING +below). The .Fl b Ar bootcode option specifies a file that contains the bootstrap code. The contents and size of the file are determined by the partitioning scheme. -For the MBR scheme, it is a 512 byte file of which the first 446 bytes -are installed as bootstrap code. The .Fl p Ar partcode option specifies a file that contains the bootstrap code intended to be written to a partition. -For the VTOC8 scheme, it is a 8192 byte file of which the last 7680 bytes -are installed as bootstrap code. The partition is specified by the .Fl i Ar index option. -For the VTOC8 scheme, if the -.Fl i Ar index -option is omitted, the bootstrap code is written to all sufficiently large -partitions. The size of the file must be smaller than the size of the partition. .Pp Additional options include: @@ -716,6 +708,91 @@ The scheme-specific attributes for PC98: .It Cm active .It Cm bootable .El +.Sh BOOTSTRAPPING +.Fx supports several partitioning schemes and each scheme uses different +bootstrap code. +The bootstrap code is located in the specific disk area for each partitioning +scheme and also it might have different size. +.Pp +The bootstrap code could be separated into two types. +The first one is embedded in the partitioning scheme's metadata, the second +type is located on the specific partition. +The embedding bootstrap code should be done only with the +.Cm gpart bootcode +command with +.Fl b Ar bootcode +option. +The GEOM PART class has knowlege on how to embed bootstrap code into specific +partitioning scheme metadata without damage. +.Pp +The Master Boot Record (MBR) uses 512-bytes bootstrap code image, embedded into +partition table's metadata area. +There are two variants of this bootstrap code: +.Pa /boot/mbr +and +.Pa /boot/boot0 . +The first one searches partition with +.Cm active +attribute (see the +.Sx ATTRIBUTES +section) in the partition table. +Then it runs next bootstrap stage. +The +.Pa /boot/boot0 +image contains a boot manager with some additional interactive functions. +.Pp +The BSD disklabel is usually created on top of the MBR partition (slice) +with type +.Cm freebsd +(see the +.Sx "PARTITION TYPES" +section). +It uses 8 KB size bootstrap code image +.Pa /boot/boot , +embedded into partition table's metadata area. +.Pp +Both types of bootstrap code are used to boot from the GUID Partition Table. +First of all, a protective MBR is embedded into first disk sector from the +.Pa /boot/pmbr +image. +It searches the +.Cm freebsd-boot +partition (see the +.Sx "PARTITION TYPES" +section) in the GPT and runs next bootstrap stage from it. +The +.Cm freebsd-boot +partition should be smaller than 545 KB. +There are two variants of bootstrap code to write to this partition: +.Pa /boot/gptboot +and +.Pa /boot/gptzfsboot . +The first one is used to boot from UFS. +It searches in the GPT partition with type +.Cm freebsd-ufs , +and it runs the thrid bootstrap stage ( +.Pa /boot/loader ) +if it is found. +The +.Pa /boot/gptzfsboot +is used to boot from ZFS. +It searches partition with type +.Cm freebsd-zfs +and starts +.Pa /boot/zfsloader +from it. +.Pp +The VTOC8 scheme does not support embedding bootstrap code. +Instead, the 8 KBytes bootstrap code image +.Pa /boot/boot1 +could be written with +.Cm gpart bootcode +command with +.Fl p Ar bootcode +option to all sufficiently large VTOC8 partitions. +To do this the +.Fl i Ar index +option could be ommited. .Sh OPERATIONAL FLAGS Actions other than the .Cm commit @@ -949,6 +1026,7 @@ and .Sh SEE ALSO .Xr dd 1 , .Xr geom 4 , +.Xr boot0cfg 8 , .Xr geom 8 .Sh HISTORY The |
