What is the minimum I have to do to create an RPM file?

As an application distributor, fpm sounds perfect for your needs. There is an example here which shows how to package an app from source. FPM can produce both deb files and RPM files.

I often do binary rpm per packaging proprietary apps - also moster as websphere - on linux. So my experience could be useful also a you, besides that it would better to do a TRUE RPM if you can. But i digress.

So the a basic step for packaging your (binary) program is as follow - in which i suppose the program is toybinprog with version 1.0, have a conf to be installed in /etc/toybinprog/toybinprog.conf and have a bin to be installed in /usr/bin called tobinprog :

1. create your rpm build env for RPM < 4.6,4.7

mkdir -p ~/rpmbuild/{RPMS,SRPMS,BUILD,SOURCES,SPECS,tmp}

cat <<EOF >~/.rpmmacros
%_topdir   %(echo $HOME)/rpmbuild
%_tmppath  %{_topdir}/tmp
EOF

cd ~/rpmbuild

2. create the tarball of your project

mkdir toybinprog-1.0
mkdir -p toybinprog-1.0/usr/bin
mkdir -p toybinprog-1.0/etc/toybinprog
install -m 755 toybinprog toybinprog-1.0/usr/bin
install -m 644 toybinprog.conf toybinprog-1.0/etc/toybinprog/

tar -zcvf toybinprog-1.0.tar.gz toybinprog-1.0/

3. Copy to the sources dir

cp toybinprog-1.0.tar.gz SOURCES/

cat <<EOF > SPECS/toybinprog.spec
# Don't try fancy stuff like debuginfo, which is useless on binary-only
# packages. Don't strip binary too
# Be sure buildpolicy set to do nothing
%define        __spec_install_post %{nil}
%define          debug_package %{nil}
%define        __os_install_post %{_dbpath}/brp-compress

Summary: A very simple toy bin rpm package
Name: toybinprog
Version: 1.0
Release: 1
License: GPL+
Group: Development/Tools
SOURCE0 : %{name}-%{version}.tar.gz
URL: http://toybinprog.company.com/

BuildRoot: %{_tmppath}/%{name}-%{version}-%{release}-root

%description
%{summary}

%prep
%setup -q

%build
# Empty section.

%install
rm -rf %{buildroot}
mkdir -p  %{buildroot}

# in builddir
cp -a * %{buildroot}


%clean
rm -rf %{buildroot}


%files
%defattr(-,root,root,-)
%config(noreplace) %{_sysconfdir}/%{name}/%{name}.conf
%{_bindir}/*

%changelog
* Thu Apr 24 2009  Elia Pinto <[email protected]> 1.0-1
- First Build

EOF

4. build the source and the binary rpm

rpmbuild -ba SPECS/toybinprog.spec

And that's all.

Hope this help