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<HTML
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>The Raw Loader</TITLE
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><H1
CLASS="SECT1"
><A
NAME="AEN162"
>The Raw Loader</A
></H1
><P
>The sources for this loader can be found in directory
<TT
CLASS="LITERAL"
>arch/alpha/boot</TT
> of the Linux kernel source
distribution. It loads the Linux kernel by reading
<TT
CLASS="LITERAL"
>START_SIZE</TT
> bytes starting at disk offset
<TT
CLASS="LITERAL"
>BOOT_SIZE+512</TT
> (also in bytes). The constants
<TT
CLASS="LITERAL"
>START_SIZE</TT
> and <TT
CLASS="LITERAL"
>BOOT_SIZE</TT
> are defined in
<TT
CLASS="LITERAL"
>linux/include/asm-alpha/system.h</TT
>. <TT
CLASS="LITERAL"
>START_SIZE</TT
>
must be at least as big as the kernel image (i.e., the size of the
<TT
CLASS="LITERAL"
>.text</TT
>, <TT
CLASS="LITERAL"
>.data</TT
>, and <TT
CLASS="LITERAL"
>.bss</TT
> segments). Similarly,
<TT
CLASS="LITERAL"
>BOOT_SIZE</TT
> must be at least as big as the image of the raw
bootstrap loader. Both constants should be an integer multiple of the
sector size, which is 512 bytes. The default values are currently 2MB
for <TT
CLASS="LITERAL"
>START_SIZE</TT
> and 16KB for <TT
CLASS="LITERAL"
>BOOT_SIZE</TT
>. Note
that if you want to boot from a 1.44MB floppy disk, you have to reduce
<TT
CLASS="LITERAL"
>START_SIZE</TT
> to 1400KB and make sure that the kernel you
want to boot is no bigger than that.</P
><P
>To build a raw loader, simply type <TT
CLASS="LITERAL"
>make rawboot</TT
> in the top
directory of your linux source tree (typically
<TT
CLASS="LITERAL"
>/usr/src/linux</TT
>). This should produce the following files in
<TT
CLASS="LITERAL"
>arch/alpha/boot</TT
>:</P
><P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>tools/lxboot</TT
>:</DT
><DD
><P
>The first
sector on the disk. It contains the offset and size of
the next file in the format described above.</P
></DD
><DT
><TT
CLASS="LITERAL"
>tools/bootlx</TT
>:</DT
><DD
><P
>The raw boot loader that
will load the file below.</P
></DD
><DT
><TT
CLASS="LITERAL"
>vmlinux.nh</TT
>:</DT
><DD
><P
>The raw kernel image consisting of
the <TT
CLASS="LITERAL"
>.text</TT
>, <TT
CLASS="LITERAL"
>.data</TT
>, and <TT
CLASS="LITERAL"
>.bss</TT
> segments of the
object file in <TT
CLASS="LITERAL"
>/usr/src/linux/vmlinux</TT
>. The
extension <TT
CLASS="LITERAL"
>.nh</TT
> indicates that this file has no object-file
header.</P
></DD
></DL
></DIV
></P
><P
>The concatenation of these three files should be written to the
disk from which you want to boot. For example, to boot from a floppy,
insert an empty floppy disk in, say, <TT
CLASS="LITERAL"
>/dev/fd0</TT
> and then type:
<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
># cat tools/lxboot tools/bootlx vmlinux >/dev/fd0</PRE
></TD
></TR
></TABLE
> </P
><P
>You can then shutdown the system and boot from the floppy by
issuing the command <TT
CLASS="LITERAL"
>boot dva0</TT
>.</P
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