Upgrade CentOS 7 to CentOS 8 using DNF Package Manager

This guide will show you how to upgrade from CentOS/RHEL 7 to CentOS/RHEL 8 using the dnf package manager. We always recommend performing these kind of task in staging before going into production.

Prerequisites

You will need one CentOS 7 server with root privileges.

Installing EPEL Repository

yum -y install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
yum -y install rpmconf yum-utils

rpmconf -a
package-cleanup --leaves
package-cleanup --orphans

Installing DNF Package Manager

yum -y install dnf
dnf -y remove yum yum-metadata-parser
rm -Rf /etc/yum

dnf -y upgrade
dnf -y install http://mirror.centos.org/centos/8/BaseOS/x86_64/os/Packages/centos-repos-8.2-2.2004.0.1.el8.x86_64.rpm
dnf -y install http://mirror.centos.org/centos/8/BaseOS/x86_64/os/Packages/centos-release-8.2-2.2004.0.1.el8.x86_64.rpm
dnf -y install http://mirror.centos.org/centos/8/BaseOS/x86_64/os/Packages/centos-gpg-keys-8.2-2.2004.0.1.el8.noarch.rpm
dnf -y upgrade https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
dnf clean all

rpm -e `rpm -q kernel`
rpm -e --nodeps sysvinit-tools

Upgrading to CentOS 8

dnf -y --releasever=8 --allowerasing --setopt=deltarpm=false distro-sync

rpmconf -a
rpm -e kernel-core
dnf -y install kernel-core

Verify that grub is updated and in the right location:

ROOTDEV=`ls /dev/*da|head -1`;
echo "Detected root as $ROOTDEV..."
grub2-install $ROOTDEV

Installing Minimal Package:

dnf -y groupupdate "Core" "Minimal Install"

Verify CentOS version:

cat /etc/centos-release

reboot

Wrapping up

You have successfully upgraded from CentOS 7 to CentOS 8 using dnf package manager and you now have a latest release of CentOS 8.