Chapter 3. Preparing software for RPM packaging To prepare a piece of software for packaging with RPM, you can first patch the software, create a LICENSE file for it, and archive it as a tarball. 3.1. Patching software When packaging software, you might need to make certain changes to the original source code, such as fixing a bug or changing a configuration file. In RPM packaging, you can instead leave the original source code intact and apply patches on it. A patch is a piece of text that updates a source code file. The patch has a diff format, because it represents the difference between two versions of the text. You can create a patch by using the diff utility, and then apply the patch to the source code by using the patch utility. Note Software developers often use Version Control Systems such as Git to manage their code base. Such tools offer their own methods of creating diffs or patching software. 3.1.1. Creating a patch file for a sample C program You can create a patch from the original source code by using the diff utility. For example, to patch a Hello world program written in C ( cello.c ), complete the following steps. Prerequisites You installed the diff utility on your system: Procedure Back up the original source code: The -p option preserves mode, ownership, and timestamps. Modify cello.c as needed: Generate a patch: Lines that start with + replace the lines that start with - . Note Using the Naur options with the diff command is recommended because it fits the majority of use cases: -N ( --new-file ) The -N option handles absent files as empty files. -a ( --text ) The -a option treats all files as text. As a result, the diff utility does not ignore the files it classified as binaries. -u ( -U NUM or --unified[=NUM] ) The -u option returns output in the form of output NUM (default 3) lines of unified context. This is a compact and an easily readable format commonly used in patch files. -r ( --recursive ) The -r option recursively compares any subdirectories that the diff utility found. However, note that in this particular case, only the -u option is necessary. Save the patch to a file: Restore the original cello.c : Important You must retain the original cello.c because the RPM package manager uses the original file, not the modified one, when building an RPM package. For more information, see Working with spec files . Additional resources diff(1) man page 3.1.2. Patching a sample C program To apply code patches on your software, you can use the patch utility. Prerequisites You installed the patch utility on your system: You created a patch from the original source code. For instructions, see Creating a patch file for a sample C program . Procedure The following steps apply a previously created cello.patch file on the cello.c file. Redirect the patch file to the patch command: Check that the contents of cello.c now reflect the desired change: Verification Build the patched cello.c program: Run the built cello.c program: 3.2. Creating a LICENSE file It is recommended that you distribute your software with a software license. A software license file informs users of what they can and cannot do with a source code. Having no license for your source code means that you retain all rights to this code and no one can reproduce, distribute, or create derivative works from your source code. Procedure Create the LICENSE file with the required license statement: Example 3.1. Example GPLv3 LICENSE file text Additional resources Sorce code examples 3.3. Creating a source code archive for distribution An archive file is a file with the .tar.gz or .tgz suffix. Putting source code into the archive is a common way to release the software to be later packaged for distribution. 3.3.1. Creating a source code archive for a sample Bash program The bello project is a Hello World file in Bash . The following example contains only the bello shell script. Therefore, the resulting tar.gz archive has only one file in addition to the LICENSE file. Note The patch file is not distributed in the archive with the program. The RPM package manager applies the patch when the RPM is built. The patch will be placed into the ~/rpmbuild/SOURCES/ directory together with the tar.gz archive. Prerequisites Assume that the 0.1 version of the bello program is used. You created a LICENSE file. For instructions, see Creating a LICENSE file . Procedure Move all required files into a single directory: Create the archive for distribution: Move the created archive to the ~/rpmbuild/SOURCES/ directory, which is the default directory where the rpmbuild command stores the files for building packages: Additional resources Hello World written in bash 3.3.2. Creating a source code archive for a sample Python program The pello project is a Hello World file in Python . The following example contains only the pello.py program. Therefore, the resulting tar.gz archive has only one file in addition to the LICENSE file. Note The patch file is not distributed in the archive with the program. The RPM package manager applies the patch when the RPM is built. The patch will be placed into the ~/rpmbuild/SOURCES/ directory together with the tar.gz archive. Prerequisites Assume that the 0.1.1 version of the pello program is used. You created a LICENSE file. For instructions, see Creating a LICENSE file . Procedure Move all required files into a single directory: Create the archive for distribution: Move the created archive to the ~/rpmbuild/SOURCES/ directory, which is the default directory where the rpmbuild command stores the files for building packages: Additional resources Hello World written in Python 3.3.3. Creating a source code archive for a sample C program The cello project is a Hello World file in C. The following example contains only the cello.c and the Makefile files. Therefore, the resulting tar.gz archive has two files in addition to the LICENSE file. Note The patch file is not distributed in the archive with the program. The RPM package manager applies the patch when the RPM is built. The patch will be placed into the ~/rpmbuild/SOURCES/ directory together with the tar.gz archive. Prerequisites Assume that the 1.0 version of the cello program is used. You created a LICENSE file. For instructions, see Creating a LICENSE file . Procedure Move all required files into a single directory: Create the archive for distribution: Move the created archive to the ~/rpmbuild/SOURCES/ directory, which is the default directory where the rpmbuild command stores the files for building packages: Additional resources Hello World written in C

Commands:
yum install diffutils
cp -p cello.c cello.c.orig
#include <stdio.h> int main(void) { printf("Hello World from my very first patch!\n"); return 0; }
diff -Naur cello.c.orig cello.c --- cello.c.orig 2016-05-26 17:21:30.478523360 -0500 + cello.c 2016-05-27 14:53:20.668588245 -0500 @@ -1,6 +1,6 @@ #include<stdio.h> int main(void){ - printf("Hello World!\n"); + printf("Hello World from my very first patch!\n"); return 0; } \ No newline at end of file
diff -Naur cello.c.orig cello.c > cello.patch
mv cello.c.orig cello.c
yum install patch
patch < cello.patch patching file cello.c
cat cello.c #include<stdio.h> int main(void){ printf("Hello World from my very first patch!\n"); return 1; }
make gcc -g -o cello cello.c
./cello Hello World from my very first patch!
vim LICENSE
cat /tmp/LICENSE This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/ .
mkdir bello-0.1 mv ~/bello bello-0.1/ mv LICENSE bello-0.1/
tar -cvzf bello-0.1.tar.gz bello-0.1 bello-0.1/ bello-0.1/LICENSE bello-0.1/bello
mv bello-0.1.tar.gz ~/rpmbuild/SOURCES/
mkdir pello-0.1.1 mv pello.py pello-0.1.1/ mv LICENSE pello-0.1.1/
tar -cvzf pello-0.1.1.tar.gz pello-0.1.1 pello-0.1.1/ pello-0.1.1/LICENSE pello-0.1.1/pello.py
mv pello-0.1.1.tar.gz ~/rpmbuild/SOURCES/
mkdir cello-1.0 mv cello.c cello-1.0/ mv Makefile cello-1.0/ mv LICENSE cello-1.0/
tar -cvzf cello-1.0.tar.gz cello-1.0 cello-1.0/ cello-1.0/Makefile cello-1.0/cello.c cello-1.0/LICENSE
mv cello-1.0.tar.gz ~/rpmbuild/SOURCES/