Understanding how to package software effectively is crucial for system administrators and developers alike, particularly on systems using the Red Hat Package Manager, or RPM. While installing pre-built packages is common, creating your own custom RPMs offers significant advantages for deploying internal applications, modified software, or ensuring consistent installations across multiple servers.
Building an RPM package essentially involves bundling your application files, defining how it should be installed, configured, and removed, and specifying its dependencies. The core of this process lies in the SPEC file. This is a meticulously structured text file that acts as the blueprint for the package. It contains metadata about the software, such as its name, version, release number, summary, and description, as well as detailed instructions for the rpmbuild utility.
The SPEC file is organized into several key sections, each introduced by a % symbol. The initial part, often called the Preamble, handles package-level details, including required dependencies (Requires), build-time dependencies (BuildRequires), conflicts, and the source files needed (Source). Following this are sections defining the build stages:
- The %prep section is where the source code is prepared, typically involving unpacking compressed archives.
- The %build section contains commands to compile the software.
- The %install section is perhaps the most critical. It dictates exactly where files should be placed within a temporary staging directory, known as the buildroot, mimicking the final installation path on the target system.
- The %files section lists every single file and directory that will be included in the final RPM package, often with permissions and ownership specified. This section ensures only intended files are packaged.
- The %changelog section is used to document changes between different versions or releases of the package.
Once the SPEC file and source files are correctly placed within the designated RPM build directory structure (often under ~/rpmbuild with subdirectories like SPECS, SOURCES, BUILDROOT, etc.), the rpmbuild command is used to create the package. A common command is rpmbuild -ba yourpackage.spec, which tells rpmbuild to build both the binary RPM (-bb) and the source RPM (-bs).
The rpmbuild utility reads the SPEC file and executes the commands within the defined sections in the correct order. It handles downloading sources (if specified), unpacking, building, installing into the buildroot, and finally packaging the contents of the buildroot and the metadata into the final .rpm file.
Building packages this way automates installations, simplifies upgrades and removals, manages dependencies effectively, and ensures consistency across environments. It is a powerful technique for professional system management on RPM based distributions.
Source: https://infotechys.com/how-to-create-and-build-rpm-packages/
