boot(8)
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BOOT26(8) NetBSD/acorn26 System Manager's Manual BOOT26(8)
NAME
boot26 -- Bootloader for NetBSD/acorn26
SYNOPSIS
*boot26 [-acdqsv] [file]
DESCRIPTION
boot26 is a program that runs under RISC OS and launches the
NetBSD/acorn26 kernel. It needs to be installed in a RISC OS filesystem
and given file type FFA (Module). The kernel it is to load also needs to
be stored in a RISC OS filesystem.
It takes the following options, which set flags in the boothowto variable
in the booted kernel (see boothowto(9)):
-a (RB_ASKNAME) Cause the kernel to prompt the user for the name
of the device containing the root filesystem. This also
causes boot26 to prompt for the name of the kernel to be
loaded.
-s (RB_SINGLE) Cause the kernel to ask init to boot into single-
user mode.
-d (RB_KDB) Cause the kernel to enter the kernel debugger as
soon as possible.
-c (RB_USERCONF) Enter the in-kernel device configuration man-
ager before attaching any devices.
-q (RB_QUIET) Cause the kernel to emit fewer messages than nor-
mal while starting up.
-v (RB_VERBOSE) Cause the kernel to emit more messages than nor-
mal while starting up.
boot26 attempts to load the kernel from the RISC OS file specified as
file, or from netbsd if file is not specified. The file must be an ELF
image, and may have been compressed using gzip(1).
Use as a module
boot26 is implemented as a RISC OS relocatable module. It can be loaded
into memory by running `*RMLoad boot26'. After this, NetBSD can be
booted by running `*boot26' as usual, but the command will be handled by
the module.
It should also be possible to arrange for boot26 to be loaded from ROM
(e.g. from the ROM on an expansion card), in which case NetBSD could be
made to boot automatically by making boot26 the configured language using
`*Configure Language'.
Screen display
When it starts up, boot26 displays the current memory map. Each charac-
ter in the map represents one page of (physical) RAM. The ticks along
the top are to stop you getting lost. The characters in the map indicate
what the memory's being used for (actually where it's logically mapped):
0 -> zero-page
+ -> boot26 workspace
* -> Free space (boot26 wants to put the kernel here)
d -> RAM disc
s -> System sprite area
m -> RMA
h -> System heap/stack
f -> Font cache
S -> Screen memory
On a machine with 32k pages (which is all NetBSD/acorn26 supports), the
left half of the first line is potential screen memory, and hence not
used by boot26. The next page is usually zero page under RISC OS, and is
used for zero page under NetBSD as well. The next is usually the system
heap under RISC OS, and is used for process 0's kernel stack under
NetBSD. The next is used for the message buffer under NetBSD. Pages
from there on are used to load the kernel, and must be free if boot26 is
to do so successfully. Future bootloaders should load the kernel into
whatever pages are free, then kick out RISC OS and shuffle them into the
right shape. This is left as an exercise for the enthusiastic reader.
FILES
/usr/mdec/boot26,ffa The location of boot26 in the NetBSD
filesystem.
SEE ALSO
gzip(1), reboot(2), ddb(4), userconf(4), init(8), boothowto(9)
HISTORY
boot26 was introduced in NetBSD 1.6 as a replacement for the original
NetBSD/arm26 bootloader, which was written in BBC BASIC.
BUGS
boot26 cannot load kernels from a NetBSD filesystem.
NetBSD 6.0.3 September 4, 2009 NetBSD 6.0.3
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