freebsd-dev/sys/boot/i386/loader/help.i386
Toomas Soome 769bad9f8a Add chain loader support for loader
Implement simple chain loader in loader; this update does add chain command,
taking device or file as argument to load and start new boot loader.

In case of BIOS, the chain will read the boot block to address 0000:7c00 and
jumps on it. In case of UEFI, the chain command is to be used with efi
application, typically stored in EFI System Partition.

The update also does add simple menu entry, if the variable chain_disk is set.
The value of the variable chain_disk is used as argument for chain loading.

Relnotes:	yes
Differential Revision:	https://reviews.freebsd.org/D5992
2017-06-16 20:08:44 +00:00

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################################################################################
# Treboot DReboot the system
reboot
Causes the system to immediately reboot.
################################################################################
# Theap DDisplay memory management statistics
heap
Requests debugging output from the heap manager. For debugging use
only.
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# Tset Snum_ide_disks DSet the number of IDE disks
NOTE: this variable is deprecated, use root_disk_unit instead.
set num_ide_disks=<value>
When booting from a SCSI disk on a system with one or more IDE disks,
and where the IDE disks are the default boot device, it is necessary
to tell the kernel how many IDE disks there are in order to have it
correctly locate the SCSI disk you are booting from.
################################################################################
# Tset Sroot_disk_unit DForce the root disk unit number.
set root_disk_unit=<value>
If the code which detects the disk unit number for the root disk is
confused, eg. by a mix of SCSI and IDE disks, or IDE disks with
gaps in the sequence (eg. no primary slave), the unit number can be
forced by setting this variable.
################################################################################
# Tsmap DDisplay BIOS SMAP table
smap
Displays the BIOS SMAP (system memory map) table.
################################################################################
# Tchain DChain load disk block
chain disk:
chain will read stage1 (MBR or VBR) boot block from specified device
to address 0000:7C00 and attempts to run it. Use lsdev to get available
device names. Disk name must end with colon.
################################################################################