RPM Installation Dependencies – Explained

You will learn how to manage dependencies during RPM installation on Linux servers such as CentOS, RHEL, Fedora, and Ubuntu. We’ll provide step-by-step instructions on how to properly handle dependency issues and solve common issues. Whether you build your own RPM or use third-party, we’ll cover it in this guide.

About RPM and Dependencies

Each RPM package contains metadata about the software, including what dependencies it has. When you attempt to install a package, RPM checks the dependencies listed in the package against the software already installed on your server. If all dependencies are met, the installation proceeds. If not, the installation fails, and RPM tells you what dependencies are missing.

Example – Apache HTTP dependency management

Let’s deep-dive to a real-world example with the Apache HTTP package. We’ll take a closer look at the process of installing this package on a CentOS system. Note that the names of Apache packages may vary across different Linux distributions; for CentOS, it is httpd.

Dependencies

The Apache HTTP Server depends on various libraries and packages. Here are some key dependencies:

• apr: Apache Portable Runtime library
• apr-util: Apache Portable Runtime Utility library
• centos-logos: CentOS-related icons and graphics, used by Apache’s default welcome page
• httpd-tools: Tools for use with the Apache HTTP Server
• mailcap: Helps the server identify MIME types
• systemd: System and service manager
• shadow-utils: Utilities for managing accounts and shadow password files.

This is not an exhaustive list, as the Apache HTTP Server might have other dependencies depending on the features you want to enable.

Installation – Under the hood

We’ll use the yum command to install the Apache HTTP Server, as it automatically resolves and installs all dependencies. Here’s how to do it:

sudo yum install httpd

During the installation process, yum checks for the dependencies required by Apache. If they’re not already installed, yum presents a list of all packages it will install or update to meet the dependencies. It will then prompt you for confirmation before proceeding. This is what it looks like:

================================================================================
 Package            Arch   Version         Repository                      Size
================================================================================
Installing:
 httpd              x86_64 2.4.37-21.el8   AppStream                      1.4 M
Installing dependencies:
 apr                x86_64 1.6.3-9.el8     AppStream                      125 k
 apr-util           x86_64 1.6.1-6.el8     AppStream                       92 k
 centos-logos       x86_64 80.5-2.el8      BaseOS                          13 M
 httpd-tools        x86_64 2.4.37-21.el8   AppStream                      104 k
 mailcap            noarch 2.1.48-3.el8    BaseOS                          39 k
 redhat-logos       x86_64 80.5-2.el8      BaseOS                          13 M
 systemd            x86_64 239-30.el8_2    BaseOS                          3.1 M
Installing weak dependencies:
 apr-util-bdb       x86_64 1.6.1-6.el8     AppStream                       27 k
 apr-util-openssl   x86_64 1.6.1-6.el8     AppStream                       27 k

By giving you a detailed list and waiting for your confirmation, yum ensures that the installation process is transparent and under your control. After you agree to the changes, yum installs Apache and all its dependencies, ensuring a safe and smooth installation process.

Handling Dependencies During RPM Installation

During an RPM installation, the system must resolve all dependencies for the process to succeed. Dependency resolution is about finding and installing all packages that the software requires to function. For example, if you want to install a package named program1.rpm, which depends on lib1.rpm and lib2.rpm, RPM won’t proceed with the installation unless both libraries are already installed.

Let’s illustrate this with a step-by-step installation on CentOS:

1. Install a package using RPM: sudo rpm -i program1.rpm
2. If lib1.rpm and lib2.rpm are not installed, RPM will output an error like: error: Failed dependencies: lib1 is needed by program1 lib2 is needed by program1
3. To resolve this, install the required libraries: sudo rpm -i lib1.rpm lib2.rpm
4. Then, retry installing the original package: sudo rpm -i program1.rpm

This should go smoothly if lib1.rpm and lib2.rpm don’t have dependencies of their own, or their dependencies are already installed. However, manual dependency resolution can get complicated for packages with many dependencies. Thankfully, we have tools like Yum and DNF that simplify the process.

Tools for Dependency Management

Yum and DNF are two tools that automatically manage dependencies during RPM installations on Fedora, CentOS, and RHEL.

In Ubuntu, you need to use Alien to convert the RPM package into a DEB package (native to Ubuntu), and then use APT (Advanced Package Tool) to handle dependencies.

Here’s a step-by-step guide for each distribution:

Ubuntu:

1. Install Alien: sudo apt-get install alien
2. Convert the RPM package to DEB: sudo alien program1.rpm
3. Install the DEB package with APT: sudo apt-get install ./program1.deb

CentOS/RHEL:

Install the package with Yum:

sudo yum install program1.rpm

Fedora:

Install the package using DNF:

sudo dnf install package.rpm

In the end, managing dependencies might seem a daunting task, but with tools like RPM, Yum, DNF, Alien, and APT, the process becomes significantly simplified and manageable.

Frequently Asked Questions (FAQ)