CentOS/7/Upgrade to Centos 8

Both distributions are end-of-life:

• CentOS 8 reached EOL on December 31, 2021.
• CentOS 7 reached EOL on June 30, 2024

# Update CentOS 7
yum update -y
reboot

# Install upgrade tools
yum install -y epel-release yum-utils rpmconf dnf

# Resolve config conflicts
rpmconf -a

# Remove orphaned packages
package-cleanup --leaves
package-cleanup --orphans

-------------


# Remove yum
dnf remove -y yum yum-metadata-parser
rm -rf /etc/yum

# Install CentOS 8 repository packages from vault
dnf install \
http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/centos-linux-repos-8-3.el8.noarch.rpm \
http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/centos-linux-release-8.5-1.2111.el8.noarch.rpm \
http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/centos-gpg-keys-8-3.el8.noarch.rpm

# Sync to CentOS 8 packages
dnf --releasever=8 \
    --allowerasing \
    --setopt=deltarpm=false \
    distro-sync -y

# Install EL8 kernel
dnf install -y kernel-core

reboot

dnf install -y yum-utils dnf rpmconf

cat > /etc/yum.repos.d/CentOS-Linux-Vault-8.5.2111.repo <<'EOF'
[baseos]
name=CentOS Linux 8.5.2111 - BaseOS
baseurl=http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

[appstream]
name=CentOS Linux 8.5.2111 - AppStream
baseurl=http://vault.centos.org/8.5.2111/AppStream/x86_64/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

[extras]
name=CentOS Linux 8.5.2111 - Extras
baseurl=http://vault.centos.org/8.5.2111/extras/x86_64/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

[powertools]
name=CentOS Linux 8.5.2111 - PowerTools
baseurl=http://vault.centos.org/8.5.2111/PowerTools/x86_64/os/
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
EOF

Dirty RHEL7 to CentOS 8

rpm -e --nodeps redhat-release-server

rpm -e --nodeps redhat-logos

Do Not Reboot Before Checking These

-------- critical checks -------

rpm -q rpm rpm-libs rpm-build-libs python3-rpm dnf python3-dnf yum
rpm -q systemd dracut kexec-tools
rpm -qa 'kernel*' | sort


## Look for EL8s for:
rpm
dnf
yum
systemd
dracut
kexec-tools
kernel-core
kernel-modules


--------- do not reboot until you show EL8 -------

rpm -qa 'kernel*' | sort
ls -l /boot/vmlinuz-*
grubby --info=ALL | egrep '^(index|kernel|title)'

rpm -qa 'kernel*' | sort | grep el8
ls -l /boot/vmlinuz-* | grep el8
grubby --info=ALL | egrep '^(index|kernel|title)'