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Update some READMEs.
author | Rob Landley <rob@landley.net> |
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date | Fri, 03 Dec 2010 21:20:28 -0600 |
parents | 3a4fccf92f58 |
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The Aboriginal Linux build scripts are the source code for the Aboriginal Linux project. If you would like to build your own cross compiler or target system image from source, use these build scripts. They're written in bash and should be fairly easy to read. If you want to download prebuilt binary cross compilers or system images, see the downloads/binaries directory (which has its own README). The rest of this README describes the contents of the current source tarball. Scripts that build code for a specific target (everything except download.sh, clean.sh, and host-tools.sh) produce output under the "build" directory, in a subdirectory with the same name as the script plus the name of the target architecture the output is built for. At the end of each stage, the result is saved to a tarball of the same name. All downloaded files wind up in the "packages" directory. Output from compiles is generated in the "build" directory. These are the only two directories the build writes to, and both directories may be deleted and then recreated by the build scripts. To do a full "distclean", do "rm -rf build packages" from the top level directory. None of these scripts need to be run as root -- a design goal of Aboriginal Linux is that root access on the host is never required. These scripts include the following stages: build.sh ARCH Top level wrapper script which builds a system image for a target, by calling most of the other scripts listed here in the appropriate order. It requires one argument, which is the target platform to build for. When run without arguments, build.sh lists available architectures. Several environment variables can be set to control the build's behavior, see the file "configure" for details. download.sh Uses wget to download the source code required by the later build stages, saving it in the "packages" directory. It compares the sha1 checksum of any existing tarballs to an expected value, only downloading new source tarballs when it needs to. If the primary site is down, it checks a series of fallback mirrors. The environment variable PREFERRED_MIRROR can insert a new mirror at the start of the list, which is checked before even the official website. This script is not target-specific, and only needs to be called once when building multiple architectures. host-tools.sh Sanitizes the host environment by building known versions of needed tools from source code, then restricting the $PATH to just those tools. This is an optional step which can be skipped, but without it the build process is very brittle. This "airlock" step serves a similar purpose to the temporary system built by Linux From Scratch's chapter 5, isolating the new system from variations in the host. It also acts as an early check that the resulting system images offer a sufficient development environment to rebuild themselves from source, because the host tool versions used to build them in the first place are the same ones the scripts install into the target root filesystem. This script populates the "build/host" directory, which is automatically used by later stages if it exists. It is not target specific, and only needs to be run once when building multiple architectures. simple-cross-compiler.sh ARCH Creates a cross compiler for the selected target architecture, built from gcc, binutils, uClibc, and the Linux kernel headers. This compiler runs on the host and produces programs that run on the target. This compiler is sufficient to build a system image for the target, but isn't as powerful as the compilers created by native-compiler.sh. It doesn't include thread support, uClibc++, or the shared version of libgcc. cross-compiler.sh ARCH This optional step creates a more full-featured cross compiler, with thread support, uClibc++, and the shared version of libgcc. (This is not required to build a system image, but the prebuilt binary compilers shipped in the downloads/binaries directory are built this way.) The build.sh wrapper script only calls this stage if CROSS_HOST_ARCH is set, indicating which host architecture to build for. (For PC hardware, i686 is a good value, since most 64 bit PCs can run 32 bit code.) This compiler is statically linked against uClibc, for maximum portability. (You can set BUILD_STATIC=none to dynamically link instead, but then have to install uClibc's shared libraries on the host.) native-compiler.sh ARCH This step creates a compiler for the selected target, using one or more of the existing simple cross compilers. The compiler it produces runs on the target and produces programs that also run on the target. By default this compiler is statically linked so you can add it to an existing target root filesystem. Use BUILD_STATIC=none to disable this. This compiler includes binutils, gcc, make, bash, and distcc. Because it's a native compiler, the executable names do not have any prefixes the way the cross compilers do. (I.E. just "ld" instead of "$ARCH-ld".) simple-root-filesystem.sh ARCH Creates a root filesystem (with uCLibc, BusyBox, and an init script) that contains just enough infrastructure to boot up to a shell prompt. root-filesystem.sh ARCH Combines the simple root filesystem and native compiler into a single root filesystem, producing a bootable root filesystem with development tools. system-image.sh ARCH Package up the root filesystem into a filesystem image (ext2, squashfs, or initramfs), build a Linux kernel configured for the target, and generate a wrapper script capable of invoking an appropriate emulator (generally qemu). run-from-build.sh ARCH Boot up a system image under its emulator, with full native development environment options (a 2 gigabyte /dev/hdb mounted on /home and distcc calling out to the appropriate cross compiler). Note that targets with the hw- prefix are aimed at actual hardware, and do not have an emulator configured. Hardware targets are derived from an existing architecture, repackaging the other architecture's root filesystem with a different Linux kernel configuration. The sources/more directory contains additional scripts the user can run, but which are not called from build.sh. This directory contains the external user interfaces the user can call directly which are not build stages. See more/README in the Aboriginal source code for details.