Downgrades all packages on a yum/redhat based system to oldest possible versions.

yum-downgrade-all.sh

#!/bin/bash

install_version() {
	# This would be: NetworkManager.x86_64         1:1.14.0-14.el8            rhel-8-baseos-rhui-rpms
	version_entry="$1"
	echo "    Attempting to install version entry: $version_entry"

	# This would be: NetworkManager.x86_64
	package_arch="$(echo $version_entry | awk -F" " '{print $1}')"
	# This would be: NetworkManager (we remove the .x86_64 or any architecture)
	package="$(echo "$package_arch" | rev | cut -d'.' -f2- | rev)"

	# This would be: 1:1.14.0-14.el8
	version_with_redhat_embellishment="$(echo $version_entry | awk -F" " '{print $2}')"
	# This would be: 1.14.0-14.el8
	version=$(echo "$version_with_redhat_embellishment" | cut -d':' -f2-)

	# This should be: NetworkManager-1.14.0-14.el8
	package_version="$package-$version"

	echo "      Normalized install package name: $package_version"
	yum downgrade -y $package_version 1>/dev/null 2>/dev/null
	[ $? -ne 0 ] && echo "      FAIL!" && return 1

	echo "      SUCCESS!"
}

install_oldest_version() {
	package="$1"
	echo "  Downgrading package $package..."

	output=$(yum --showduplicates list available $package 2>/dev/null)

	#Set the field separator to new line
	IFS=$'\n'

	found_available_packages=""
	oldest_package_line=""

	for line in $output; do
		if [ "$found_available_packages" == "true" ]; then
			install_version "$line"
			[ $? -eq 0 ] && break
		elif [[ "$line" == *"Available Packages"* ]]; then
			found_available_packages="true"
		fi
	done
}

skip_package() {
	package="$1"
	
	# skip authselect since it can prevent any logins, especially on EC2.
	if [[ "$package" == *"authselect"* ]]; then
		return 1
	fi
}

echo "Downgrades all packages to oldest possible versions."

echo "Finding installed packages..."
installed=$(yum list installed | awk -F" " '{print $1}')

echo "  Found $(echo $installed | wc -c) packages installed."

echo ""
echo "For each package, attempting to downgrade to oldest possible version..."
for package in $installed; do
	# should this package be skipped for whatever reason?
	skip_package "$package"
	[ $? -ne 0 ] && echo "Skipping package $package" && continue
	
	install_oldest_version "$package"
done