how can I create an RPM from a subdir?

I have a subdir my_sw that has an image of what I want to install:

my_sw/
  usr/
    bin/
       foo
    man/
       man1/
         foo.1

and so on. I imagine there must be a simple way to create a spec file and use rpmbuild to package this up as an RPM so other users can install it. I don't care about any of the fancy build stuff rpm can do, I just want it to install that dir tree. (I suppose I'm misusing rpm a bit, but this way my users will have my files tracked in their rpm database, which they'd like.)

I've tried various things, but rpm wants to do way more than I want it to, and most projects want rpm to do lots more as well (pre-building, building, testing things, stripping, etc.) Is there a howto somewhere showing how to just put together a trivial rpm that just installs files?

I'm doing this on CentOS 5 or 6 (or similar RedHat).

Solution

Yes, you can create RPMs from a filesystem image such as you describe. It is one of the easier cases for RPM building, but you still have to use the tools.

The steps are roughly:

1) Create an RPM building environment, if you have not already done so. At its barest, that would be a subdirectory tree under your home directory, like so:

rpm/
  BUILD/
  RPMS/
    x86_64/  (or whatever is the applicable arch)
  SOURCES/
  SPECS/
  SRPMS/

2) Create a tarball of the image, and drop it in the SOURCES/ directory.

3) Create a spec file in the SPEC/ subdirectory. There are tools that can help you create a spec file skeleton. For example, if the "rpmdevtools" package is available to you (which it is for CentOS 5 and 6) then you can use "rpmdev-newspec". You will need to fill in some fields and provide some (minor, in your case) shell commands. The result might be something like this:

Name:    my_sw
Summary: Cool software
Version: 1.0
Release: 1
Group:   Applications
License: <license>
Source0: my_sw.tar.gz

%description
my_sw does awesome things that you'll really like.  If you have any need for
awesomeness, this is for you!

%prep
# different from the default:
%setup -q -c -T

%build
# nothing to do

%install
# Start clean
rm -rf %{buildroot}
mkdir -p %{buildroot}

# Put the files in the correct location relative to %{buildroot}
ln -s %{buildroot} ./my_sw
tar xzf %{S:0}

%files
%defattr(-,root,root,-)
%{_bindir}/foo
%{_mandir}/man1/foo.1

%changelog
* Wed Aug 27 2014 Gary O <[email protected]> 1.0-1
- Initial spec

Some of that goes into the ultimate RPM; the rest tells rpmbuild details of what it needs to do.

4) Build it with rpmbuild:

rpmbuild -ba SPECS/my_sw.spec

5) The binary RPM will be in RPMS/. The source RPM will be in SRPMS/.

One of the best RPM building references I have ever found is the Fedora Project's RPM guide: http://docs.fedoraproject.org/en-US/Fedora_Draft_Documentation/0.1/html/RPM_Guide/index.html. See especially chapter 9.