source: README.BLFS

1. INTRODUCTION::

     To automate package builds from the BLFS book instructions is a huge
  task. Some of the issues are: the BLFS book isn't linear; some package
  pages use a custom layout; there are circular dependencies; several
  packages can be installed on a non-default prefix; build commands can
  change based on what dependencies will be used, etc.

     That being said, the goal of the blfs-tool is to help you solve package
  dependencies, create build scripts and a Makefile. Not all the auto-generated
  build scripts and Makefile will work "as is", thus, as a general rule,
  you will need to review and edit the scripts while reading the book.

     The blfs tools allow also to update packages from the LFS book. LFS
  packages which may be updated appear in the menu interface. When selected,
  their scriptlet is generated in the same manner as for BLFS packages.
  (TODO: presently, when an LFS package needs a patch, you'll have to
  donwload it manually to your $SRC_ARCHIVE directory (usually /sources)).

2. PREREQUISITES::

     In addition to a full LFS system, the following packages and their
  dependencies are needed by this tool:
    - required: libxml2, libxslt, DocBook XML DTD
    - recommended: wget (to download the package tarballs) and sudo (to build
      as a user)
    - optional: lynx (allows to read the generated linearized book), GPM (to
      cut and paste commands from the book), git (to update the book
      sources)
  Note that the optional dependencies are recommended for ease of use of the
  tool.

     You should also have the following personal skills:
    - Ability to write and debug shell scripts: as said in the introduction,
      not all the generated scripts can be used directly. They need to be
      edited to produce an error free build.
    - Ability to debug build failures, like missing dependencies or
      installation directories not known to the system (when you install in
      /opt for example).
    - Ability to choose the tools you need to configure and administrate
      your system: in the BLFS book, nothing is mandatory, nothing is
      useless. You are on your own in choosing what to build, but wrong
      decisions may lead to a non functional system...

3. INSTALL::

     There are two ways to install the BLFS tools on an LFS system, described
  in paragraphs 3.1 and 3.2, respectively:

  3.1 INSTALLATION ON A RUNNING SYSTEM

     Select "Use Book --> Beyond Linux From Scratch" in the jhalfs menu:
  The tools are installed in $HOME$BLFS_ROOT (the default for $BLFS_ROOT
  is /blfs_root). The BLFS book is downloaded or copied to its directory.
  The tracking directory (see below) is created (if it does not already
  exist) and initialized. Before running "make", you should ensure the
  tracking directory (default location /var/lib/jhalfs/BLFS) can be:
    - either created by the user running "make", if it does not exist
    - or that it is writable by the user running "make", if it exists.

  After the intallation, you should perform the following additional steps:
    - Configure sudo, adding the needed privileges for the user.
    - Although it is not strictly necessary, it is recommended to install
      the bash shell startup files (as per `3. After LFS Configuration
      Issues' of the BLFS book), as some instructions in BLFS rely on
      their being present.
    - At this point, the tool has no way to know which versions of LFS packages
      are installed, so that the menu interface will show all the LFS packages,
      as if they were not installed. If you have a released version of LFS, or
      the date of your GIT version of LFS is known, you should run the
      update-lfs.sh script. If you have updated some
      LFS packages since first installation, or have been using a custom
      working copy of the LFS book, the only (tedious) way is to create
      empty files with names <package>-<installed-version> in the tracking
      directory, and run the tool.

    - If you have also installed some BLFS packages, they are not in the
      tracking file. The only way is to create empty files with names
      <package>-<installed-version> in the tracking directory, and run the tool.

  3.2 INSTALLATION ON A JUST BUILT LFS SYSTEM

    For books that support it (only LFS),
  there is an option to install the BLFS tools right after building
  the LFS system: just tick `BOOK Settings/Add blfs-tool support' in
  jhalfs configuration menu. The tools are installed in $BLFS_ROOT
  (default /blfs_root) on the LFS system, and the dependencies are built
  at the end of the jhalfs run, before the custom tools.

  After booting the new LFS system some steps are needed to finish
  the installation of the automated tools:

    - A user account must be created. You must be logged on that user
      account to use blfs-tool. This is not strictly necessary,
      since the packages can be built as root, too, but it is
      never a good idea to build packages as root.

    - Move /blfs-root to that user's home and change ownership of the
      directory and files to the user.

    - Give the user read and write privileges over the $TRACKING_DIR
      directory and the files that it contains.

    - Configure sudo and add the bash shell startup files, as described
      above

    - Note that the versions of LFS packages are automatically known to
      the tool in this case, and there is no need to run the update-lfs.sh
      script.

     We assume that the BLFS tools will be used on a booted LFS system.
  Using them to build BLFS packages in a chroot jail is also possible,
  but not supported.

  3.3 DIRECTORY LAYOUT IN THE $BLFS_ROOT DIRECTORY

    blfs-xml/*                  GIT tree of the selected BLFS book version
    lfs-xml/*                   GIT tree of the selected LFS book version
    lib/constants.inc           functions libraries
       /func_dependencies         for building the dependency tree
    menu/*                      menuconfig source code
    xsl/gen_pkg_list.xsl        XSL stylesheet to generate the package database
       /gen_config.xsl          XSL stylesheet to generate the Config.in file
                                for use in the menuconfig system
       /dependencies.xsl        XSL stylesheet to generate the dependency list
                                of a package
       /make_book.xsl           XSL stylesheet to generate the linear book.xml
       /lfs_make_book.xsl       XSL stylesheet to incoporate LFS pages into the
                                linear book.xml
       /scripts.xsl             XSL stylesheet to generate the scriptlets from
                                book.xml
       /bump.xsl                XSL stylesheet to update the tracking file
       /process-install.xsl     XSL stylesheet included by scripts.xsl, for
                                outputting cleanly install instructions
       /process-replaceable.xsl XSL stylesheet included by scripts.xsl, for
                                generating correct instructions when a
                                <replaceable> tag is encountered.
    README.BLFS                 this file
    TODO                        developers notes (well, not updated often)
    gen_pkg_book.sh             resolves dependencies, generates a linear BLFS
                                book, and finally generates build scripts
    gen-makefile.sh             generates the target Makefile
    progress_bar.sh             the target Makefile progress bar
    gen-special.sh              Helper script for generating the package
                                database
    Makefile                    Used by make to update the package database
                                from the GIT tree, then launch the menuconfig
                                interface, and run gen_pkg_book.sh based on
                                configuration settings
    packdesc.dtd                a simple DTD describing the format of the
                                package database and the tracking file.

  Working files: several files are generated when first running the tool:

    packages.xml            auto-generated package database
    Config.in               input file for the menu driven choices
    configuration           file generated by the menuconfig process
    dependencies/*          files recording the dependency tree
    book.xml                the linearized book
    book-html/*             the linearized book rendered in html
    scripts/*               the scriptlets

  3.4 INSTALLED PACKAGES TRACKING SYSTEM:

       This tool includes a very simple tracking system to log which packages
    have been installed using the tool. It is used to skip installed packages
    from target selection menu and to test if an installed package has been
    updated in the BLFS book. Do not rely on this feature as a package
    management tool.

       The tracking system itself is an XML file: instpkg.xml. It is
    initialized when <make> is first run in blfs_root. It resides in a
    directory, which is created when needed during the process of building
    custom tools or blfs dependencies, right after LFS. You can specify
    that directory location in the blfs-tools sub-menu of jhalfs. You may
    need to update permissions and/or ownership of this directory before
    using the blfs tool (see README in jhalfs).

       The default location of the tracking directory is /var/lib/jhalfs/BLFS.
    NB : after the initial build, that directory is only used to contain
    instpkg.xml, unless custom tools have been built. In the latter case,
    it also contains empty files whose name are "$PKG-$VERSION" for each
    versionned package built. The information about those packages is
    included into instpkg.xml the next time the tool is run.

4. USAGE::

       From now on, all the work must be done from inside the installation
    root directory.

       Due to the complexity of the BLFS book, the scripts and Makefile
    generation is done in several steps:

  4.1  UPDATING BOOK SOURCES::

       If you are using the development book version and you want to update
    installed packages to the latest version found in that book, you need to
    update the XML sources and packages database. To do that, run
    "make update". This is not necessary if you just built LFS, and you
    can skip to step 4.2.

       On the next configuration run, packages already installed but listed
    with a new version in the book will be available for target selection
    and used to solve dependencies.

  4.2  CONFIGURING AND PARSING THE BOOK::

       The next step is to create a book and build scripts in dependency
    build order for one or several packages.

       Run <make> to launch the configuration interface. The main menu contains
    four blocks: individual package selection, Build settings, Build layout,
    and Optimization.

       In the package selection block, menus and submenus are organized
    as the book's parts, chapters and sections. You can navigate those menus
    and select as many targets as you want. But we suggest to not select
    too many at a time to be able to sort issues!

       In the "Build settings" submenu, the dependency level and default
    packages used to solve alternatives are set (currently, only for the MTA).
    You can also select whether the build will be made as a normal user or as
    root, whether to use "porg style" package management, whether to remove
    ".la" files, and wheter statistics for the package are generated (build
    time, memory footprint and "DESTDIR" install). If you use package
    management, you have to enter the path to the packInstall.sh script too.

       In the "Build layout" submenu, you can select where the source tarballs
    reside and are downloaded, where the packages are built, and whether to
    keep the build tree after installation.

       In the "Optimization" submenu, you can select the number of parallel
    jobs, and set the usual CFLAGS, CXXFLAGS, and LDFLAGS. the special
    keyword "EMPTY" can be used for those flags to ensure they are unset.

       Note that there are help strings associated to those menus. Please
    read them for details!

       Those settings are saved to be reused in future configuration runs.

       When you are done with the menu, a few checks occur, and the dependency
    chain is generated. Each dependency appears with its priority (required,
    recommended, optional, or external), and it's level. There is a root level
    1. The selected packages have level 2. The dependencies of selected packages
    have level 3, the dependencies of the dependencies have level 4, and so on.
    When circular dependencies are found, they appear with a priority of
    "circular". This means that two (or more) dependency chains arrive at the
    same package. The algorithm chooses the chain with the highest priority and
    reorders dependencies to remove the other chain(s). This is not always the
    solution an user would prefer, but we have found no way to do it better.

       You end up with a book.xml file which contains the linearized book,
    and a rendered HTML, in the directory book-html, which you can browse with
    "lynx book-html/index.html" (or with any other browser).

       Furthermore, there is a directory "scripts", which contains the generated
    scriptlets.

       There is yet another directory, "dependencies" that contains files
    generated while resolving dependencies.

  4.3  EDITING BUILD SCRIPTS::

       Now it is time to review the generated book and scripts, making any
    changes to the scripts necessary to fix generation bugs or to suit your
    needs.

       Scripts for additional packages (i.e., for non-BLFS packages) can be
    easily inserted. For example, if you want to install the external dependency
    "bar" before "foo" package and the "foo" script is named "064-z-foo", you
    just need to create a "064-y-bar" build script.

       Remember, the package tracking system isn't a package management tool
    and knows nothing about packages not in the BLFS book.

  4.4  CREATING THE MAKEFILE::

       When the build scripts are ready to be run, the Makefile can be
    created. Create an empty subdirectory (for example "mkdir work") and cd
    to that directory. Then run ../gen-makefile.sh. Note that the directory
    is completely emptied before generating the Makefile, so to prevent
    erasing useful data, the script ensures that the name of the current
    working directory starts with "work".

    Review the Makefile, and, if all looks sane, start the build by running
    "make".

5. GENERATED BUILD SCRIPTS ISSUES::

      In this section, known issues with the generated build scripts are
   discussed. They are due to build procedures and/or BLFS layout
   particularities that we can't handle. In several cases, editing the
   build scripts is mandatory.
      You may also need to insert some build scripts created by you to resolve
   unhandled dependencies and/or to remove some script installing an unneeded
   package (unneeded packages may be pulled in the dependency chain, if
   they occur as an "or" with another package).
      When there are circular dependencies (only one known in BLFS 8.0 for
   recommended dependencies), you may need to move around scripts so that they
   run in the order script-A script-B script-A. This involves copying script-A
   to another name (using the xxx-a- fields), and possibly renaming the xxx-a-
   fields of each involved script.

   5.1  BLFS BOOTSCRIPTS::

        Normally, bootscript installation should work. On the other hand, the
     book does not give instruction for running them, so you might have to
     manually insert "/etc/init.d/rc.d/<initscript> start" at some place during
     the build.

   5.2  PACKAGE CONFIGURATION::

        For those packages that have a "Configuration" section, you should
     edit the build script to fit the needs of your system. Sometimes, the
     bash startup files are modified. The generated scripts contain a
     line 'source /etc/profile', which ensures that the proper environment
     variables are used.

   5.3  PAGES WITH TWO OR MORE PACKAGES::

        For example: sane, poppler, audacious, freetts, which, etc.

        On the pages for those packages, the BLFS book actually has instructions
     to download and install two or more packages. You must edit the scripts to
     fix this. A common pitfall is that the variable PACKAGE may be used for
     several tarballs. Be sure to save the PACKAGE variable to some other
     name (for example PKG1, PKG2, etc) after each download. The unpacking
     instructions may need to be repeated for each tarball in turn.

   5.4  XORG7

        The book has special page layouts for the Xorg7 packages. The tool
     breaks those pages into individual pages for each packages in the linear
     book. Also, the menu gives the choice to select each package individually.

        To build the whole Xorg7 chapter, select xinit. The (recommended)
     dependency chain brings in the whole set of Xorg packages.

   5.5  PATCHES

        Please, make sure that all scripts have the commands to download/apply
     the required patches. Due to book layout issues, some patches may be
     missing (as of BLFS 8.0, all the patches seem to be downloaded).

   5.6  ROOT COMMANDS

        If building as a normal user (the default setting), be sure that all
     commands that require root privileges are run using sudo. Also make sure
     necessary root privilege commands are visible in your PATH. The scripts
     ensure that /usr/sbin is appended to the user's PATH when running
     privileged commands.

        For commands necessitating root privileges, the generated scripts wrap
     them with the construct:
       sudo -E sh -e << ROOT_EOF
         <commands to be executed as root with `$', ``', and `\' escaped>
       ROOT_EOF
     The "-e" switch to sh ensures the command block exits with error if an
     error occurs. The "-E" switch to sudo ensures the whole environment is
     passed to the commands to be run with root privileges. It is effective
     only if the /etc/sudoers file contains `Defaults setenv', or SETENV in
     the user attributes (this is implicit if the command the user is allowed
     to run is `ALL'). If you think it is a security issue, you may forbid
     this flag in /etc/sudoers, but then, you have to un-escape `$' for
     variables coming from the environment in the instructions. Although this
     construct is rather strong, it can fail in some corner cases, so
     carefully review those instructions.

        Due to book layout issues, some sudo commands may be missing.

   5.7  OTHERS

        There may be other issues that we are not aware of. If you find
     any, please report it to <alfs-discuss@linuxfromscratch.org>.