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><H1
CLASS="SECT1"
><A
NAME="AEN703"
>6. Putting them together: Making the diskette(s)</A
></H1
><P
>At this point you have a kernel and a compressed root filesystem. If you are
making a boot/root disk, check their sizes to make sure they will both fit on
one disk. If you are making a two disk boot+root set, check the root
filesystem to make sure it will fit on a single diskette.</P
><P
> You should decide whether to use LILO to boot the bootdisk kernel.
The alternative is to copy the kernel directly to the diskette and boot
without LILO. The advantage of using LILO is that it enables you to supply
some parameters to the kernel which may be necessary to initialize your
hardware (Check the file <TT
CLASS="FILENAME"
>/etc/lilo.conf</TT
> on your
system. If it exists and has a line like
``<TT
CLASS="LITERAL"
>append=...</TT
>'', you probably need this feature). The
disadvantage of using LILO is that building the bootdisk is more
complicated and takes slightly more space. You will have to set up a small
separate filesystem, which we shall call the <EM
>kernel
filesystem</EM
>, where you transfer the kernel and a few other files
that LILO needs.</P
><P
> If you are going to use LILO, read on; if you are going to transfer
the kernel directly, skip ahead to <A
HREF="x703.html#TRANSFERRINGWITHOUTLILO"
>Section 6.2</A
>.</P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="TRANSFERRINGWITHLILO"
>6.1. Transferring the kernel with LILO</A
></H2
><P
>First, make sure you have a recent version of LILO.</P
><P
>You must create a small configuration file for LILO.
It should look like this:
<TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="PROGRAMLISTING"
> boot =/dev/fd0
install =/boot/boot.b
map =/boot/map
read-write
backup =/dev/null
compact
image = KERNEL
label = Bootdisk
root =/dev/fd0</PRE
></FONT
></TD
></TR
></TABLE
>
For an explanation of these parameters, see LILO's user documentation. You
will probably also want to add an <TT
CLASS="LITERAL"
>append=...</TT
> line to
this file from your hard disk's <TT
CLASS="FILENAME"
>/etc/lilo.conf</TT
> file.</P
><P
>Save this file as <TT
CLASS="FILENAME"
>bdlilo.conf</TT
>.</P
><P
> You now have to create a small filesystem, which we shall call a
<EM
>kernel filesystem</EM
>, to distinguish it from the root
filesystem.</P
><P
>First, figure out how large the filesystem should be. Take the size of your
kernel in blocks (the size shown by ``<B
CLASS="COMMAND"
>ls -s KERNEL</B
>'') and
add 50. Fifty blocks is approximately the space needed for inodes plus other
files. You can calculate this number exactly if you want to, or just use 50.
If you're creating a two-disk set, you may as well overestimate the space since
the first disk is only used for the kernel anyway. Call this number
<TT
CLASS="LITERAL"
>KERNEL_BLOCKS</TT
>.</P
><P
>Put a floppy diskette in the drive (for simplicity we'll assume
<TT
CLASS="FILENAME"
>/dev/fd0</TT
>) and create an ext2 kernel filesystem on it:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> mke2fs -N 24 -m 0 /dev/fd0 KERNEL_BLOCKS</PRE
></FONT
></TD
></TR
></TABLE
>
The ``<TT
CLASS="LITERAL"
>-N 24</TT
>'' specifies 24 inodes, which is all you should
need for this filesystem. Next, mount the filesystem, remove the
<TT
CLASS="FILENAME"
>lost+found</TT
> directory, and create <TT
CLASS="FILENAME"
>dev</TT
>
and <TT
CLASS="FILENAME"
>boot</TT
> directories for LILO:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> mount -o dev /dev/fd0 /mnt
rm -rf /mnt/lost+found
mkdir /mnt/{boot,dev}</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
>Next, create devices <TT
CLASS="FILENAME"
>/dev/null</TT
> and
<TT
CLASS="FILENAME"
>/dev/fd0</TT
>. Instead of looking up the device numbers, you
can just copy them from your hard disk using <TT
CLASS="LITERAL"
>-R</TT
>:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> cp -R /dev/{null,fd0} /mnt/dev</PRE
></FONT
></TD
></TR
></TABLE
>
LILO needs a copy of its boot loader, <TT
CLASS="FILENAME"
>boot.b</TT
>, which
you can take from your hard disk. It is usually kept in the
<TT
CLASS="FILENAME"
>/boot</TT
> directory.
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> cp /boot/boot.b /mnt/boot</PRE
></FONT
></TD
></TR
></TABLE
>
Finally, copy in the LILO configuration file you created in the last section,
along with your kernel. Both can be put in the root directory:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> cp bdlilo.conf KERNEL /mnt</PRE
></FONT
></TD
></TR
></TABLE
>
Everything LILO needs is now on the kernel filesystem, so you are ready to run
it. LILO's <TT
CLASS="LITERAL"
>-r</TT
> flag is used for installing the boot loader on some other
root:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> lilo -v -C bdlilo.conf -r /mnt</PRE
></FONT
></TD
></TR
></TABLE
>
LILO should run without error, after which the kernel filesystem
should look something like this:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
>total 361
1 &#8211;rw&#8211;r&#8211;&#8211;r&#8211;&#8211; 1 root root 176 Jan 10 07:22 bdlilo.conf
1 drwxr&#8211;xr&#8211;x 2 root root 1024 Jan 10 07:23 boot/
1 drwxr&#8211;xr&#8211;x 2 root root 1024 Jan 10 07:22 dev/
358 &#8211;rw&#8211;r&#8211;&#8211;r&#8211;&#8211; 1 root root 362707 Jan 10 07:23 vmlinuz
boot:
total 8
4 &#8211;rw&#8211;r&#8211;&#8211;r&#8211;&#8211; 1 root root 3708 Jan 10 07:22 boot.b
4 &#8211;rw&#8211;&#8211;&#8211;&#8211;&#8211;&#8211;&#8211; 1 root root 3584 Jan 10 07:23 map
dev:
total 0
0 brw&#8211;r&#8211;&#8211;&#8211;&#8211;&#8211; 1 root root 2, 0 Jan 10 07:22 fd0
0 crw&#8211;r&#8211;&#8211;r&#8211;&#8211; 1 root root 1, 3 Jan 10 07:22 null </PRE
></FONT
></TD
></TR
></TABLE
></P
><P
>Do not worry if the file sizes are slightly different from yours.</P
><P
>Now leave the diskette in the drive and go to <A
HREF="x703.html#SETTINGRAMDISKWORD"
>Section 6.3</A
>.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="TRANSFERRINGWITHOUTLILO"
>6.2. Transferring the kernel without LILO</A
></H2
><P
>If you are <EM
>not</EM
> using LILO, transfer the kernel to the
bootdisk with <B
CLASS="COMMAND"
>dd</B
>:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> % dd if=KERNEL of=/dev/fd0 bs=1k
353+1 records in
353+1 records out</PRE
></FONT
></TD
></TR
></TABLE
>
In this example, <B
CLASS="COMMAND"
>dd</B
> wrote 353 complete records + 1
partial record, so the kernel occupies the first 354 blocks of the
diskette. Call this number <TT
CLASS="LITERAL"
>KERNEL_BLOCKS</TT
> and
remember it for use in the next section.</P
><P
>Finally, set the root device to be the diskette itself, then set the
root to be loaded read/write:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> rdev /dev/fd0 /dev/fd0
rdev -R /dev/fd0 0</PRE
></FONT
></TD
></TR
></TABLE
>
Be careful to use a capital <TT
CLASS="LITERAL"
>-R</TT
> in the second
<B
CLASS="COMMAND"
>rdev</B
> command.</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="SETTINGRAMDISKWORD"
>6.3. Setting the ramdisk word</A
></H2
><P
>
Inside the kernel image is the <EM
>ramdisk word</EM
> that
specifies where the root filesystem is to be found, along with other
options. The word can be accessed and set via the <B
CLASS="COMMAND"
>rdev</B
>
command, and its contents are interpreted as follows:
<DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN782"
></A
><P
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
WIDTH="96"
ALIGN="RIGHT"
VALIGN="TOP"
>Bit field</TH
><TH
WIDTH="100%"
ALIGN="LEFT"
VALIGN="TOP"
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
WIDTH="96"
ALIGN="RIGHT"
VALIGN="TOP"
>0-10</TD
><TD
WIDTH="100%"
ALIGN="LEFT"
VALIGN="TOP"
>Offset to start of ramdisk, in 1024 byte blocks</TD
></TR
><TR
><TD
WIDTH="96"
ALIGN="RIGHT"
VALIGN="TOP"
>11-13</TD
><TD
WIDTH="100%"
ALIGN="LEFT"
VALIGN="TOP"
>unused</TD
></TR
><TR
><TD
WIDTH="96"
ALIGN="RIGHT"
VALIGN="TOP"
>14</TD
><TD
WIDTH="100%"
ALIGN="LEFT"
VALIGN="TOP"
>Flag indicating that ramdisk is to be loaded</TD
></TR
><TR
><TD
WIDTH="96"
ALIGN="RIGHT"
VALIGN="TOP"
>15</TD
><TD
WIDTH="100%"
ALIGN="LEFT"
VALIGN="TOP"
>Flag indicating to prompt before loading rootfs</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></P
><P
>If bit 15 is set, on boot-up you will be prompted to place a new floppy
diskette in the drive. This is necessary for a two-disk boot set.</P
><P
>There are two cases, depending on whether you are building a single
boot/root diskette or a double ``boot+root'' diskette set.</P
><P
></P
><OL
TYPE="1"
><LI
><P
> If you are building a single disk, the compressed root filesystem
will be placed right after the kernel, so the offset will be the first free
block (which should be the same as
<TT
CLASS="LITERAL"
>KERNEL_BLOCKS</TT
>). Bit 14 will be set to 1, and bit
15 will be zero.
For example, say you're building a single disk and the root filesystem will
begin at block 253 (decimal). The ramdisk word value should be 253
(decimal) with bit 14 set to 1 and bit 15 set to 0. To calculate the value
you can simply add the decimal values. 253 + (2^14) = 253 + 16384 =
16637. If you don't quite understand where this number comes from, plug it
into a scientific calculator and convert it to binary,</P
></LI
><LI
><P
>If you are building a two-disk set, the root filesystem will begin at
block zero of the second disk, so the offset will be zero. Bit 14 will be
set to 1 and bit 15 will be 1. The decimal value will be
2^14 + 2^15 = 49152 in this case.</P
></LI
></OL
><P
>After carefully calculating the value for the ramdisk word, set it with
<B
CLASS="COMMAND"
>rdev -r</B
>. Be sure to use the
<EM
>decimal</EM
> value. If you used LILO, the argument to
<B
CLASS="COMMAND"
>rdev</B
> here should be the <EM
>mounted kernel
path</EM
>,
e.g. <TT
CLASS="FILENAME"
>/mnt/vmlinuz</TT
>; if you copied the kernel with
<B
CLASS="COMMAND"
>dd</B
>, instead
use the floppy device name (<EM
>e.g.,</EM
> <TT
CLASS="FILENAME"
>/dev/fd0</TT
>).
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> rdev -r KERNEL_OR_FLOPPY_DRIVE VALUE</PRE
></FONT
></TD
></TR
></TABLE
></P
><P
>If you used LILO, unmount the diskette now.</P
><DIV
CLASS="IMPORTANT"
><P
></P
><TABLE
CLASS="IMPORTANT"
WIDTH="100%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="../images/important.gif"
HSPACE="5"
ALT="Important"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>Do not believe what the rdev/ramsize manpage says about ramdisk
size.
The manpage is obsolete. As of kernel 2.0 or so, the ramdisk word no
longer determines the ramdisk size; the word is instead interpreted
according to the table at the beginning of section <A
HREF="x703.html#SETTINGRAMDISKWORD"
>Section 6.3</A
>. For a detailed
explanation, see the documentation file <A
HREF="file:/usr/src/linux/Documentation/ramdisk.txt"
TARGET="_top"
>ramdisk.txt</A
> or
<A
HREF="http://www.linuxhq.com/kernel/v2.4/doc/ramdisk.txt.html"
TARGET="_top"
>http://www.linuxhq.com/kernel/v2.4/doc/ramdisk.txt.html</A
>.
</P
></TD
></TR
></TABLE
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN831"
>6.4. Transferring the root filesystem</A
></H2
><P
>The last step is to transfer the root filesystem.</P
><P
>&#13;<P
></P
><UL
><LI
><P
> If the root filesystem will be placed on the
<EM
>same</EM
> disk as the kernel, transfer it using
<B
CLASS="COMMAND"
>dd</B
> with the <TT
CLASS="OPTION"
>seek</TT
> option, which
specifies how many blocks to skip:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> dd if=rootfs.gz of=/dev/fd0 bs=1k seek=<EM
>KERNEL_BLOCKS</EM
></PRE
></FONT
></TD
></TR
></TABLE
></P
></LI
><LI
><P
>If the root filesystem will be placed on a <EM
>second</EM
>
disk, remove the first diskette, put the second diskette in the drive, then
transfer the root filesystem to it:
<TABLE
BORDER="1"
BGCOLOR="#E0E0E0"
WIDTH="90%"
><TR
><TD
><FONT
COLOR="#000000"
><PRE
CLASS="SCREEN"
> dd if=rootfs.gz of=/dev/fd0 bs=1k</PRE
></FONT
></TD
></TR
></TABLE
></P
></LI
></UL
>&#13;</P
><P
>Congratulations, you are done! </P
><DIV
CLASS="IMPORTANT"
><P
></P
><TABLE
CLASS="IMPORTANT"
WIDTH="100%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="../images/important.gif"
HSPACE="5"
ALT="Important"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>You should always test a bootdisk before putting it aside for an emergency.
If it fails to boot, read on.</P
></TD
></TR
></TABLE
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