.TH 9BOOT 8
.SH NAME
9bootfat, 9bootiso, 9boothyb, 9bootpxe, bootia32.efi, bootx64.efi, efiboot.fat \- PC bootloader for FAT, ISO and PXE network booting
.SH SYNOPSIS
Started by PC BIOS/EFI or chainloaded by partition bootsector
.SH DESCRIPTION
9boot is the bootloader used on PCs to start the Plan 9 kernel.
Its task is to read and parse the
.IR plan9.ini (8)
configuration file, gather some basic system information like
the amount of usable system memory, do some basic system
initialization and load the kernel from the boot media into memory.

After reading the configuration, the loader will automatically 
attempt to boot the kernel that was specified by the
.B bootfile=
parameter. If there is no such parameter, a key
gets pressed on the keyboard or the kernel file was not
found then the loader enters the interactive
boot console.

The syntax of the boot console is the same as in the
.IR plan9.ini (8)
file with
.IB key = value
pairs setting boot parameters. In addition a few command
words are recognized that are intended for interactive use:
.TP
.BI clear [prefix]
can be used to remove parameters from the configuration.
If a
.IR prefix
is specified, the first parameter that matches the prefix
is removed. If the
.IR prefix
argument is omitted, the whole configuration will be reset.
.TP
.B show
displays the current configuration in memory.
.TP
.B wait
will return to the console prompt after processing the
configuration file preventing automatic boot.
.TP
.B boot
will end the console and attempt booting the kernel.
.SS
There are many ways to boot a PC so
.IR 9boot
was split into a number of distinct programs one for each boot
method.
.SH FAT BOOTING
When booting Plan 9 from a harddisk or USB pen drive, a
FAT16/32 partition
.IR (9fat) 
is used to store the kernel and 
.IR plan9.ini (8)
configuration. Due to size limitations, instead of loading
the kernel directly, the bootsector
.IR (pbs)
of the FAT partition loads
a 2nd stage bootloader 
.IR (9bootfat)
from the root directory of the filesystem.
.SH CD-ROM BOOTING
Booting from CD-ROM requires only the 
.IR 9bootiso
bootloader to be included in the ISO-9660 image under
.BR /386/9bootiso ,
set as a non-emulation bootblock (see
.B -B
in
.IR mk9660 (8)).
Boot parameters are read from
.BR /cfg/plan9.ini .
.SH ISO HYBRID BOOTING
With the
.I 9boothyb
loader, an ISO image can be made into a bootable disk by
creating a MBR and appending a bootable DOS partition containing
.I 9boothyb
renamed to
.IR 9bootfat .
The loader will read the ISO filesystem as if it were stored
on a CD-ROM drive.
.SH NETWORK BOOTING
With a PXE capable BIOS and network card one can download
.IR 9bootpxe
and boot the kernel from a TFTP server (see
.IR dhcpd (8)
and
.IR ndb (6)
for details). Once started,
.IR 9bootpxe
will read the file
.B /cfg/pxe/$ether
or, if this file is not present,
.B /cfg/pxe/default
from the tftp server, where
.B $ether
is the MAC address of the client's network card
in lower case hex, and uses this as its
.IR plan9.ini (8)
file.
.SH EFI BOOTING
EFI firmware looks for the files
.I bootia32.efi
(for 386)
or
.I bootx64.efi
(for amd64)
in the boot media and executes them.
For local disk media, these files are located in the directory
.B /efi/boot
of the 
.B FAT
formatted boot partition.
For 
.B CD-ROM
media, the boot partition is provided
as a embedded 
.B FAT
filesystem image
.I efiboot.fat
(see
.B -E
in
.IR mk9660 (8)).
In the network boot case, the
.I bootia32.efi
or
.I bootx64.efi
files are used as the
.B BSP
program instead of
.IR 9bootpxe .
Once started, the boot media 
.RB ( PXE ,
.BR ISO ,
.BR FAT )
is discovered and
.IR plan9.ini (8)
configuration is read from it in the same way as
with the BIOS-based
.I 9boot*
loaders.

.SH FILES
.B /386/pbs
.br
.B /386/9bootfat
.br
.B /386/9bootiso
.br
.B /386/9boothyb
.br
.B /386/9bootpxe
.br
.B /386/bootia32.efi
.br
.B /386/bootx64.efi
.br
.B /386/efiboot.fat
.SH SOURCE
.BR /sys/src/boot/pc
.br
.BR /sys/src/boot/efi
.br
.SH "SEE ALSO"
.IR plan9.ini (8),
.IR mk9660 (8),
.IR dhcpd (8),
.IR ndb (6)
.SH HISTORY
9boot first appeared in 9front (April, 2011).
EFI support first appeared in 9front (Oct, 2014).