Rolf Veen (Updated 4 Dec 2003)
The objective of this document is to describe the steps needed to build a GNU/Linux system from its sources, introducing at the same time some innovations:
The build process is based on two scripts and some OGDL descriptors. OGDL is a simple data language very appropiate for configuration files (see ogdl.org). The two scripts are:
The method described here is oriented towards developers. Many aspects are not covered and it is purely experimental. For a pedagogic approach to building a GNU/Linux system see Linux From Scratch.
In this context, we call profile to a set of descriptors, scripts and patches needed to build a particular GNU/Linux system. The profile does not include the sources of the packages itself.
Each profile needs, as starting point, a Linux installation with development tools included, one that is able to compile the packages that make up the chroot environment. The exact prerequisites depend on the system we are going to build and is out of the scope of this document.
Additionally we need a directory filled with the original sources and patches, by default $SRC/in. In order to know what source packages are needed, each master build script has an option 'info' that lists them.
|/src/in||Input directory, where sources are to be found|
|/src/root||The base environment (chroot)|
|/src/work||Where packages are unpacked and build|
First unpack hlinuxutils somewhere and then do:
make make check make install
hlinuxutils provides the needed tools and also one example profile, based on LFS and BLFS (see again Linux From Scratch).
The build script first checks if all the needed source files are available in /src/in. If that is ok, it then executes the pre target found in the descriptor. Then it builds the packages in the order they appear in the descriptor, and finally executes the post target. While building packages, a summary file is generated that records starting and ending times and disk usage of each package.
Here is a fragment a build descriptor:
title 'Basic packages' description \ The packages in this set substitute the transition packages used to initially creating the chroot. version 1.0 targets pre \ echo 'Setting environment' set +h export LC_ALL=POSIX export PATH=/bin:/tools/bin umask 022 unset CPP CXX CC LD_LIBRARY LD_PRELOAD CFLAGS CXXFLAGS LDFLAGS defaults target build packages linux ( version 2.4.23; target headers2; noclean ) linux ( version 2.4.23; target install; nounpack )
Here is a frament of a summary file:
cyrus-sasl-2.1.15 build_install starttime 1068646332 s diskfree_before 464217 kB endtime 1068646595 s diskfree_after 399975 kB
cd /src/profile ./build chroot
This will create a small Linux distribution suitable for chroot'ing to, and that has all its commands statically build or linked against the new glibc in order to serve as a neutral base on which to build packages. This environment provides isolation from the host system.
./enter-chroot1 cd /src/profile ./build base
src profile=default -p linux-2.4.22
This command builds a kernel using the 'default' configuration and places it in /pkg/linux/. The different pre-made configuration files should be located in /src/packages/linux/conf. The kernel is build with the 'make oldconfig' option.
This command takes as input the chroot'ed environment with the packages built, and makes a layout suitable for a bootable CD. It also produces the final ISO image.
As an alternative, one can build a distribution that is bootable right from the same disk, without interfering with the original installation. This is ideal for testing purposes. The command to build it is different than the one that produces a CD ISO image:
If the distribution is build in the default location then a complete Linux hierarchy is available in /pkg-src/BOOT, and can be booted into by specifying an alternative init at the boot prompt:
boot: linux init="/pkg-src/BOOT/bin/init2"
!map title- * description- * targets- !map * !sh [...] defaults target * packages * ( version *; target- *; ** ) [...]
META def unit !enum ( s, kB ) * * !map starttime !int !unit endtime !int !unit diskfree_before !int !unit diskfree_after !int !unit [...]