How to upgrade CentOS from 7 to 8 ​

The new version of CentOS 8 offers the latest technologies, packages, and services and will continue to be supported until 2029. There is no official way to upgrade from CentOS 7 to CentOS 8, but unofficially it can be done. Production servers should not use such a procedure. Take a snapshot of your VPS before upgrading, so that you can restore it if necessary. So let’s start the upgrading process.

Step 1: Cleaning Up your current system

You should clean up your current system before you install CentOS 8 in order to avoid leftovers, unneeded packages, or conflicts.

First, ensure your system is up to date. Run the following command:

# yum update -y 

Install epel-release repository:

# yum install -y epel-release

Install the yum-utils and rpmconf packages:

# yum install -y yum-utils rpmconf

We’ll use rpmconf now that it has been installed to resolve our rpm packages:

# rpmconf -a

Lastly, ensure that any orphaned or unneeded packages have been removed:

package-cleanup --leaves
package-cleanup --orphans

Step 2: Replacing Packages

The next step involves replacing the important package and repository repositories with their CentOS 8 equivalents.  

Install the DNF package manager, which uses rpm packages:

# yum install -y dnf

Remove the yum package manager:

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

You should then run a DNF system update:

# dnf upgrade -y

Next, install the CentOS 8 packages:

# dnf install http://mirror.centos.org/centos/8/BaseOS/x86_64/os/Packages/{centos-release-8.1-1.1911.0.8.el8.x86_64.rpm,centos-gpg-keys-8.1-1.1911.0.8.el8.noarch.rpm,centos-repos-8.1-1.1911.0.8.el8.x86_64.rpm}

And upgrade the EPEL repository:

# dnf -y upgrade https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm

As a last step, delete all temporary files:

# dnf clean all

Step 3: Install the New Kernel and Release

Installation of the new Linux kernel and the new CentOS 8 release is the last step in switching over to CentOS 8.

First, remove the old kernel:

# rpm -e `rpm -q kernel`

If there are any conflicting packages, remove them:

# rpm -e --nodeps sysvinit-tools

Upgrade CentOS 8:

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

To install the new kernel core, follow the command:

# dnf -y install kernel-core

After that, Run the CentOS 8 Minimal install:

# dnf -y groupupdate "Core" "Minimal Install"

Based on the os-release and redhat-release files, you can verify your CentOS version. Thanks for reading! I hope it was informative for you!