source: README.BLFS@ e2dd7c4

$Id$

1. INTRODUCTION::

     If you want to add blfs-tool support into an xLFS base system build,
  read the "BLFS_TOOL SUPPORT" section found in the README and be sure
  to follow the after-booting installation instructions.

     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.


2. PREREQUISITES::

     To use this tool you MUST:

     - have experience building BLFS packages
     - know how to edit and write shell scripts
     - know how a Makefile works
     - be able to trace build failures and to find what is causing it
       (user error, package bug, BLFS command bug, or jhalfs code bug)

     If you do not have the above skills, please don't use this tool.


3. USAGE::

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

  3.1  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 xLFS. 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.

  3.2  BLFS_TOOL INSTALLATION::

    3.2.1 Normal install
       The tools are installed just after the building of xLFS, if the
    appropriate options have been selected in the building menu, as per
    jhalfs README. If you forgot to select the options and xLFS has been
    built, it is possible to go back to selecting the appropriate
    BLFS tools options in the jhalfs menu, then tick `Run makefile'
    and not `Rebuild files'. You obtain a /blfs_root directory in the
    root directory of the new xLFS system, which contains the followings:

    blfs-xml/*              SVN tree of the selected BLFS book version
    lib/constants.inc       functions libraries 
       /func_dependencies     for building the dependency tree
    menu/*                  lxdialog and 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
       /scripts.xsl         XSL stylesheet to generate the scriptlets from
                            book.xml
       /bump.xsl            XSL stylesheet to update the tracking file
    README.BLFS             this file
    TODO                    developers notes (well, not updated often)
    gen_pkg_book.sh         resolves dependencies and generates linear BLFS
                            books and 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 SVN 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.
    envars.conf             envars needed when running the target build scripts

    3.2.2 Install to an already running LFS/BLFS system
       If you forgot to install the tools when building xLFS, or want to try
    the tools, you can just run the install-blfs-tools.sh script. It will
    create the above hierarchy in your home directory and initialize the
    tracking file. You have first to make sure that the tracking dir exists
    and is writable by the user. You may also populate it with (empty) files
    whose names are of the form package-version, for installed packages, so
    that they are included into the tracking file.
    3.3.3 Working files
        Several files are generated during the process:

    packages.xml            auto-generated packages 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

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

       You may move that directory to the $HOME of a non root user, or build
    as root from that directory.

  3.3  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. This is not necessary if
    you just built xLFS, and you can skip to step 3.4.

       To do that, run "make update". It may happen that the subversion
    version of your building host is older than the version you just
    built. This may generate weird errors like "'.' omitted". The easiest
    thing to do in that case, is to completely remove the blfs-xml directory
    and run "make update". With recent versions of subversion, you can also
    run "svn upgrade" from inside the blfs-xml directory.

       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.

  3.4  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
    two blocks: individual package selection, and build options.

       In the build options section, the dependencies 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.
    Those settings are saved to be reused in future configuration runs.

       Note that you may select as many targets as you want, not just one
    as in the previous version of this tool. But we suggest to not select
    too many at a time to be able to sort issues!

       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
    0. The selected packages have level 1. The dependencies of selected packages
    have level 2, the dependencies of the dependencies have level 3, 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 also another directory, "dependencies" that contains files
    generated while resolving dependencies.

  3.5  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.

      Also, review and edit envars.conf. This file is used to set global envars
    needed by the build scripts.

  3.6  CREATING THE MAKEFILE::

       When the build scripts are ready to be run, the Makefile can be
    created. Create an empty directory (for example "mkdir work") and cd
    to that directory. Then run ../gen-makefile.sh

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

4. 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.

   4.1  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.

   4.2  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 shipped 'envars.conf' contains a
     line 'source /etc/profile', which ensures that the proper environment
     variables are used.

   4.3  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.

   4.4  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 twm. The (recommended)
     dependency chain brings in the whole set of Xorg packages.

   4.5  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).

   4.6  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. Or use
     the `Defaults secure_path=' in /etc/sudoers.

        For commands necessitating root privileges, the generated scripts wrap
     them with the construct:
       sudo -E sh << ROOT_EOF
         <commands to be executed as root with `$', ``', and `\' escaped>
       ROOT_EOF
     The -E switch ensures the whole environment is passed to the
     commands to be run with root privileges. It is effective only if the
     /etc/sudoers file contains `Defaults setenv', or SETENV in the user
     attributes. If you think it is a security issue, you may forbid this
     flag in /etc/sudoers, but then, you have to un-escape `$' 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.

        WARNING: One variable from the environment is not passed through the
     -E switch, namely PATH. This is because "sudo" always reset the PATH to
     the default "secure_path". If you need to have the same PATH as the user
     "root" would have, you may want to add "source /etc/profile" at the
     beginning of the commands to be executed as root.

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

   4.7  OTHERS

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