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<html>
<! $FreeBSD$ >
<head>
<title><center>Details of building process</center></title>
</head>
<body>
<h1><center> Details of building process.</center></h1>
<p>For those of you who really want to know what's going on behind the scene,
and can't quite deduce it from scripts themselves, here's short description of
the build process:</p>
<ul>
<li> The './build' script sets the basic parameters of the floppy, such as:
<ul>
<li> LANGUAGE: language of the various system messages, and C locale.
Available choices are: "en" (English) and "pl" (Polish).
</li>
<li>
SIZE: size of the memory filesystem (MFS), which will contain all the
binaries (except the kernel). Make it big enough for all the pieces to
fit, but keep it as small as possible (remember that running system
needs some space in /var and /tmp!). Presently, "dial" type of floppy
requires at least SIZE=1700, and others require ca. 2800 (numbers
are in kB).
</li>
<li>
TYPE: determines which set of programs and which trees will be
installed on the floppies. This simply acts as a selector to dive into
respective subdirectories in ../. Presently, the TYPE can be one of:
"dial" (dialup floppy), "net" (networking floppy), "router" (router
floppy) or "isp" (work in progress - not really usable yet).
</li>
</ul>
<li>
Then the './build' scripts checks if there is a kernel built on basis
of previously set parameters. The check is error prone, but is simple:
the target config file is called PICOBSD-${TYPE}.${SIZE}, and if there
exists a file called /sys/compile/PICOBSD-${TYPE}.${SIZE}/kernel, then
it is assumed it's the right one.
<p> If there is no such file, the script starts compilation of the kernel,
using template in ../${YTPE}/conf/PICOBSD, and adding parameters which
determine the built-in MFS size.</p>
<li>
Then the './build' script starts the consecutive stages of the build
process, which are performed by scripts (in the following order):
stage1, populate, stage2, stage3.
</li>
<li>
'stage1' prepares the file called fs.PICOBSD with given size - it's a
placeholder for the future MFS. Next, it turns it into device (using
vnconfig), and then performs some tricks :-) which allow for
doing 'disklabel'. I use the 'auto' option to disklabel(8), which
behaves strangely in 2.2.x - what it's supposed to do is to
automagically determine the disk parameters from the underlying
device (in this case, /dev/rvn0). This works ok in 3.0-current, and
allows for using arbitrary (>1024kB) MFS sizes.
<p> One notable exception here is with the "router" floppy - I use one
of extended floppy formats (820kB).</p>
<p> After the file is labelled, the newfs(8) is run. Here you can adjust
the parameter -i, which can gain you some space on the MFS (sacrificing
available number of inodes, so be careful).</p>
<p> Such prepared blank filesystem is mounted on /mnt. Here the stage1
ends.</p>
</li>
<li>
'populate', as its name suggests, transfers all the pieces which will
reside in MFS, to the filesystem mounted on /mnt. This includes:
<ul>
<li> copying language dependent files from ../${TYPE}/lang/</li>
<li> making the MFS hierarchy according to informations in
../${TYPE}/mfs.tree/ subdir.
<p> The MFS tree includes the /etc, which will contain the startup file
/etc/rc.
This file in turn doesn't do anything useful except copying the
real /etc hierarchy from the floppy filesystem. (There's one possible
improvement which comes to my mind - to have the whole /etc on the
floppy in tar.gz - this would require only one inode to store the whole
/etc, and we could gain some kB on the floppy)</p>
</li>
<li> making and installing the set of crunched programs, basing on the
description in ../${TYPE}/crunch1/crunch.conf. This involves
making the 'crunch', copying it to /mnt and making hard links to
the names of all the programs contained therein.</li>
<li> preparing a short list of kernel symbols, which will be used by
various utilities at runtime. In case of "net" and "isp" floppy, it also
prepares the kvm_kernel.db database, which will be used by such
programs as ps, netstat and others</li>
<li> preparing the list of "virgin" configuration of devices in kernel -
this list will be used by kget(8) program to save the changes to
/kernel.config file.</li>
</ul>
</li>
<li>
'stage2' prepares the target kernel. It takes the filesystem contained
in fs.PICOBSD (which has all the above pieces inside), and writes it
into the target kernel. Then it kzip(8)'s such construed kernel. This
process also strips the symbols from the kernel (that's why we prepared
the symbol list earlier).
</li>
<li>
'stage3' does almost the same as 'stage1', but this time it prepares
the filesystem of the target floppy. Default size for the floppy is
set at 1440kB.
<p> After preparing the filesystem (which again involves doing disklabel(8)
and newfs(8) - here you can notice that the resulting FS has very small
number of inodes in order to save space), the script transfers the
floppy hierarchy (which is
taken from ../${TYPE}/floppy.tree). Notice that it also contains
the /etc directory - its contents is copied right after bootup to the
real /etc in MFS. This allows for changing the system behaviour
(because you can't change the MFS contents without recompiling).</p>
<p> The script finally copies previously prepared kernel to the floppy
filesystem. The filesystem is unmounted, and here the build process
ends.</p>
</li>
</ul>
<h6>
Last modified:
@DATE@
</h6>
|
