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# 6. Building RPMs

Building RPMs is fairly easy to do, especially if you can get the software you are trying to package to build on its own. We assume here that you know how to build software from source. If you don't you probably shouldn't be starting with this document.

The basic procedure to build an RPM is as follows:

- Get the source code you are building the RPM for to build on your system.

- Make a patch of any changes you had to make to the sources to get them to build properly.

- Make a spec file for the package.

- Make sure everything is in its proper place.

- Build the package using RPM.

Under normal operation, RPM builds both binary and source packages.

## 6.1. The Spec File

We'll begin with discussion of the spec file. Spec files are required to build a package. The spec file is a description of the software along with instructions on how to build it and a file list for all the binaries that get installed.

You'll want to name your spec file according to a standard convention. It should be the package name-dash-version number-dash-release number-dot-spec. This will ensure that if you install multiple source RPMs for different versions of the same package that at least the spec files remain intact.

Here is a small spec file (eject-2.0.2-1.spec):

    Summary: A program that ejects removable media using software control.
    Name: eject
    Version: 2.0.2
    Release: 3
    Copyright: GPL
    Group: System Environment/Base
    Source: http://metalab.unc.edu/pub/Linux/utils/disk-management/eject-2.0.2.tar.gz
    Patch: eject-2.0.2-buildroot.patch
    BuildRoot: /var/tmp/%{name}-buildroot

    %description
    The eject program allows the user to eject removable media
    (typically CD-ROMs, floppy disks or Iomega Jaz or Zip disks)
    using software control. Eject can also control some multi-
    disk CD changers and even some devices' auto-eject features.

    Install eject if you'd like to eject removable media using
    software control.

    %prep
    %setup -q
    %patch -p1 -b .buildroot

    %build
    make RPM_OPT_FLAGS="$RPM_OPT_FLAGS"

    %install
    rm -rf $RPM_BUILD_ROOT
    mkdir -p $RPM_BUILD_ROOT/usr/bin
    mkdir -p $RPM_BUILD_ROOT/usr/man/man1

    install -s -m 755 eject $RPM_BUILD_ROOT/usr/bin/eject
    install -m 644 eject.1 $RPM_BUILD_ROOT/usr/man/man1/eject.1

    %clean
    rm -rf $RPM_BUILD_ROOT

    %files
    %defattr(-,root,root)
    %doc README TODO COPYING ChangeLog

    /usr/bin/eject
    /usr/man/man1/eject.1

    %changelog
    * Sun Mar 21 1999 Cristian Gafton <gafton@redhat.com>
    - auto rebuild in the new build environment (release 3)

    * Wed Feb 24 1999 Preston Brown <pbrown@redhat.com>
    - Injected new description and group.

    [ Some changelog entries trimmed for brevity.  -Editor. ]

## 6.2. The Header

The header has some standard fields in it that you need to fill in. There are a few caveats as well. The fields must be filled in as follows:

- Summary: This is a one line description of the package.

- Name: This must be the name string from the rpm filename you plan to use.

- Version: This must be the version string from the rpm filename you plan to use.

- Release: This is the release number for a package of the same version (ie. if we make a package and find it to be slightly broken and need to make it again, the next package would be release number 2).

- Copyright: This line tells how a package is copyrighted. You should use something like GPL, BSD, MIT, public domain, distributable, or commercial.

- Group: This is a group that the package belongs to in a higher level package tool or the Red Hat installer.

- Source: This line points at the HOME location of the pristine source file. It is used if you ever want to get the source again or check for newer versions. Caveat: The filename in this line MUST match the filename you have on your own system (ie. don't download the source file and change its name). You can also specify more than one source file using lines like:

      Source0: blah-0.tar.gz
      Source1: blah-1.tar.gz
      Source2: fooblah.tar.gz

  These files would go in the SOURCES directory. (The directory structure is discussed in a later section, "The Source Directory Tree".)

- Patch: This is the place you can find the patch if you need to download it again. Caveat: The filename here must match the one you use when you make YOUR patch. You may also want to note that you can have multiple patch files much as you can have multiple sources. ] You would have something like:

      Patch0: blah-0.patch
      Patch1: blah-1.patch
      Patch2: fooblah.patch

  These files would go in the SOURCES directory.

- Group: This line is used to tell high level installation programs (such as Red Hat's gnorpm) where to place this particular program in its hierarchical structure. You can find the latest description in /usr/doc/rpm*/GROUPS. The group tree currently looks something like this:

      Amusements/Games
      Amusements/Graphics
      Applications/Archiving
      Applications/Communications
      Applications/Databases
      Applications/Editors
      Applications/Emulators
      Applications/Engineering
      Applications/File
      Applications/Internet
      Applications/Multimedia
      Applications/Productivity
      Applications/Publishing
      Applications/System
      Applications/Text
      Development/Debuggers
      Development/Languages
      Development/Libraries
      Development/System
      Development/Tools
      Documentation
      System Environment/Base
      System Environment/Daemons
      System Environment/Kernel
      System Environment/Libraries
      System Environment/Shells
      User Interface/Desktops
      User Interface/X
      User Interface/X Hardware Support

- BuildRoot: This line allows you to specify a directory as the "root" for building and installing the new package. You can use this to help test your package before having it installed on your machine.

- %description It's not really a header item, but should be described with the rest of the header. You need one description tag per package and/or subpackage. This is a multi-line field that should be used to give a comprehensive description of the package.

## 6.3. Prep

This is the second section in the spec file. It is used to get the sources ready to build. Here you need to do anything necessary to get the sources patched and setup like they need to be setup to do a make.

One thing to note: Each of these sections is really just a place to execute shell scripts. You could simply make an sh script and put it after the %prep tag to unpack and patch your sources. We have made macros to aid in this, however.

The first of these macros is the %setup macro. In its simplest form (no command line options), it simply unpacks the sources and cd's into the source directory. It also takes the following options:

- `-n name` will set the name of the build directory to the listed name. The default is $NAME-$VERSION. Other possibilities include $NAME, ${NAME}${VERSION}, or whatever the main tar file uses. (Please note that these "$" variables are not real variables available within the spec file. They are really just used here in place of a sample name. You need to use the real name and version in your package, not a variable.)

- `-c` will create and cd to the named directory before doing the untar.

- `-b #` will untar Source# before cd'ing into the directory (and this makes no sense with `-c` so don't do it). This is only useful with multiple source files.

- `-a #` will untar Source# after cd'ing into the directory.

- `-T` This option overrides the default action of untarring the Source and requires a `-b 0` or `-a 0` to get the main source file untarred. You need this when there are secondary sources.

- `-D` Do not delete the directory before unpacking. This is only useful where you have more than one setup macro. It should only be used in setup macros after the first one (but never in the first one).

The next of the available macros is the %patch macro. This macro helps automate the process of applying patches to the sources. It takes several options, listed below:

- # will apply Patch# as the patch file.

- `-p #` specifies the number of directories to strip for the patch(1) command.

- `-P` The default action is to apply Patch (or Patch0). This flag inhibits the default action and will require a `0` to get the main source file untarred. This option is useful in a second (or later) %patch macro that required a different number than the first macro.

- You can also do %patch# instead of doing the real command: %patch # -P

- `-b extension` will save originals as `filename.extension` before patching.

That should be all the macros you need. After you have those right, you can also do any other setup you need to do via sh type scripting. Anything you include up until the %build macro (discussed in the next section) is executed via sh. Look at the example above for the types of things you might want to do here.

## 6.4. Build

There aren't really any macros for this section. You should just put any commands here that you would need to use to build the software once you had untarred the source, patched it, and cd'ed into the directory. This is just another set of commands passed to sh, so any legal sh commands can go here (including comments).

| Your current working directory is reset in each of these sections to the toplevel of the source directory, so keep that in mind. You can cd into subdirectories if necessary.

The variable `RPM_OPT_FLAGS` is set using values in /usr/lib/rpm/rpmrc. Look there to make sure you are using values appropriate for your system (in most cases you are). Or simply don't use this variable in your spec file. It is optional.

## 6.5. Install

There aren't really any macros here, either. You basically just want to put whatever commands here that are necessary to install. If you have make install available to you in the package you are building, put that here. If not, you can either patch the makefile for a make install and just do a make install here, or you can hand install them here with sh commands. You can consider your current directory to be the toplevel of the source directory.

The variable `RPM_BUILD_ROOT` is available to tell you the path set as the Buildroot: in the header. Using build roots are optional but are highly recommended because they keep you from cluttering your system with software that isn't in your RPM database (building an RPM doesn't touch your database...you must go install the binary RPM you just built to do that).

## 6.6. Cleaning your system

It's a good idea to always make sure there is a clean build root before building a package a second time on a system. The %clean macro will help with that. Simply put the proper commands there to blow away a former build root. Anal, err, careful folks may want to test that `RPM_BUILD_ROOT` wasn't set to / before doing something this volatile.

## 6.7. Optional pre and post Install/Uninstall Scripts

You can put scripts in that get run before and after the installation and uninstallation of binary packages. A main reason for this is to do things like run ldconfig after installing or removing packages that contain shared libraries. The macros for each of the scripts is as follows:

- %pre is the macro to do pre-install scripts.

- %post is the macro to do post-install scripts.

- %preun is the macro to do pre-uninstall scripts.

- %postun is the macro to do post-uninstall scripts.

The contents of these sections should just be any sh style script, though you do not need the #!/bin/sh.

## 6.8. Files

This is the section where you must list the files for the binary package. RPM has no way to know what binaries get installed as a result of make install. There is NO way to do this. Some have suggested doing a find before and after the package install. With a multiuser system, this is unacceptable as other files may be created during a package building process that have nothing to do with the package itself.

There are some macros available to do some special things as well. They are listed and described here:

- %doc is used to mark documentation in the source package that you want installed in a binary install. The documents will be installed in /usr/doc/$NAME-$VERSION-$RELEASE. You can list multiple documents on the command line with this macro, or you can list them all separately using a macro for each of them.

- %config is used to mark configuration files in a package. This includes files like sendmail.cf, passwd, etc. If you later uninstall a package containing config files, any unchanged files will be removed and any changed files will get moved to their old name with a .rpmsave appended to the filename. You can list multiple files with this macro as well.

- %dir marks a single directory in a file list to be included as being owned by a package. By default, if you list a directory name WITHOUT a %dir macro, EVERYTHING in that directory is included in the file list and later installed as part of that package.

- %defattr allows you to set default attributes for files listed after the defattr declaration. The attributes are listed in the form (mode, owner, group) where the mode is the octal number representing the bit pattern for the new permissions (like chmod would use), owner is the username of the owner, and group is the group you would like assigned. You may leave any field to the installed default by simply placing a - in its place, as was done in the mode field for the example package.

- %files -f <filename> will allow you to list your files in some arbitrary file within the build directory of the sources. This is nice in cases where you have a package that can build it's own filelist. You then just include that filelist here and you don't have to specifically list the files.

The biggest caveat in the file list is listing directories. If you list /usr/bin by accident, your binary package will contain every file in /usr/bin on your system.

## 6.9. Changelog

This is a log of what changes occurred when the package is updated. If you are modifying an existing RPM it is a good idea to list what changes you made here.

The format is simple. Start each new entry with a line with a * followed by the date, your name, and your email address. The date should appear in the same format that is output by:

    	date +"%a %b %d %Y"

The rest of the section is a free text field, but should be organized in some coherent manner.

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