In this article, you will learn how to upgrade CentOS 7 to CentOS 8.5 release. The steps described herein do not depict the official upgrade and this should not be applied to a production server yet.
Step 1: Install the EPEL Repository
To start off, install the EPL repository by running:
# yum install epel-release -y

Step 2: Install yum-utils Tools
After successfully installing EPEL, install yum-utils by running the command below.
# yum install yum-utils

Thereafter, you need to resolve RPM packages by executing the command.
# yum install rpmconf # rpmconf -a

Next, perform a clean-up of all the packages you don’t require.
# package-cleanup --leaves # package-cleanup --orphans

Step 3: Install the dnf in CentOS 7
Now install the dnf package manager which is the default package manager for CentOS 8.
# yum install dnf

You also need to remove the yum package manager using the command.
# dnf -y remove yum yum-metadata-parser # rm -Rf /etc/yum

Step 4: Upgrading CentOS 7 to CentOS 8
We are now ready to upgrade CentOS 7 to CentOS 8, but before we do so, upgrade the system using the newly install dnf package manager.
# dnf upgrade

Next, install CentOS 8 release package using dnf as shown below. This will take a while.
# dnf install http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/{centos-linux-repos-8-3.el8.noarch.rpm,centos-linux-release-8.5-1.2111.el8.noarch.rpm,centos-gpg-keys-8-3.el8.noarch.rpm}
Note: CentOS 8 is dead and all the repos have been moved to vault.centos.org.

Next, upgrade the EPEL repository.
dnf -y upgrade https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm

After successfully upgrading the EPEL repository, remove all the temporary files.
# dnf clean all
Remove the old kernel core for CentOS 7.
# rpm -e `rpm -q kernel`

Next, be sure to remove conflicting packages.
# rpm -e --nodeps sysvinit-tools
Thereafter, launch the CentOS 8 system upgrade as shown.
# dnf -y --releasever=8 --allowerasing --setopt=deltarpm=false distro-sync

Note: If you get errors about conflicting packages, for example in my case there were conflicts about the existing python36-rpmconf package. I removed this package, similarly if you get any conflicts just remove those packages and try running the above upgrade command.
Step 5: Install the New Kernel Core for CentOS 8
To install a new kernel for CentOS 8, run the command.
# dnf -y install kernel-core

Finally, install CentOS 8 minimal package.
# dnf -y groupupdate "Core" "Minimal Install"
Now you can check the version of CentOS installed by running.
# cat /etc/redhat-release

If you see the above output, I have successfully upgraded from CentOS 7 to CentOS 8.5 release.
Read Also: How to Set Up Automatic Updates for CentOS 8
Conclusion
This article concludes on how you can upgrade from CentOS 7 to CentOS 8. We hope you found this insightful.
Hi Ravi, I am having issues when I try to – Next, install CentOS 8 release package using dnf as shown below. This will take a while.
# dnf install http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/{centos-linux-repos-8-3.el8.noarch.rpm,centos-linux-release-8.5-1.2111.el8.noarch.rpm,centos-gpg-keys-8-3.el8.noarch.rpm}
CentOS-7 - Base 0.0 B/s | 0 B 00:00
CentOS-7 - Updates 0.0 B/s | 0 B 00:00
CentOS-7 - Extras 0.0 B/s | 0 B 00:00
Failed to synchronize cache for repo 'base', ignoring this repo.
Failed to synchronize cache for repo 'updates', ignoring this repo.
Failed to synchronize cache for repo 'extras', ignoring this repo.
Last metadata expiration check: 0:01:24 ago on Thu 02 Feb 2023 04:42:15 PM UTC.
[MIRROR] centos-linux-repos-8-3.el8.noarch.rpm: Curl error (56): Failure when receiving data from the peer for http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/centos-linux-repos-8-3.el8.noarch.rpm [Recv failure: Connection reset by peer]
[FAILED] centos-linux-repos-8-3.el8.noarch.rpm: Curl error (56): Failure when receiving data from the peer for http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/centos-linux-repos-8-3.el8.noarch.rpm [Recv failure: Connection reset by peer]
Curl error (56): Failure when receiving data from the peer for http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/centos-linux-repos-8-3.el8.noarch.rpm [Recv failure: Connection reset by peer]
Any suggestions/thoughts?
Thanks
Sunil
@Sunil,
Check your system timezone, date, and time, and set the time and date to the current date…
Thanks, Ravi!
Changed the time and time zone. Now I am unable to remove the old kernel and also unable to upgrade the kernel version.
Any help here
Thanks
Sunil
@Sunil,
There could be three reasons for getting a such error:
1. Incorrect date and time settings
2. Old dnf cache expired
3. CentOS baseURL
Fix these issues by:
Hi Ravi, The server is in USA EST, so I set it to EST time.
Still getting the same error –
[[email protected]~]# dnf install http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/{centos-linux-repos-8-3.el8.noarch.rpm,centos-linux-release-8.5-1.2111.el8.noarch.rpm,centos-gpg-keys-8-3.el8.noarch.rpm}
CentOS-7 - Base 0.0 B/s | 0 B 00:00
CentOS-7 - Updates 0.0 B/s | 0 B 00:00
CentOS-7 - Extras 0.0 B/s | 0 B 00:00
Failed to synchronize cache for repo 'base', ignoring this repo.
Failed to synchronize cache for repo 'updates', ignoring this repo.
Failed to synchronize cache for repo 'extras', ignoring this repo.
Last metadata expiration check: 22:11:40 ago on Mon 06 Feb 2023 11:54:47 AM EST.
[MIRROR] centos-linux-repos-8-3.el8.noarch.rpm: Curl error (56): Failure when receiving data from the peer for http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/centos-linux-repos-8-3.el8.noarch.rpm [Recv failure: Connection reset by peer]
[FAILED] centos-linux-repos-8-3.el8.noarch.rpm: Curl error (56): Failure when receiving data from the peer for http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/centos-linux-repos-8-3.el8.noarch.rpm [Recv failure: Connection reset by peer]
Curl error (56): Failure when receiving data from the peer for http://vault.centos.org/8.5.2111/BaseOS/x86_64/os/Packages/centos-linux-repos-8-3.el8.noarch.rpm [Recv failure: Connection reset by peer]
@Sunil,
It seems your curl doesn’t support SSL/TLS properly. Try to update or upgrade your system with:
Hi Ravi, Still no luck
Complete!
[[email protected] ~]#
@Sunil,
It looks like your repos are empty, I suggest you check the repos in /etc/yum.repos.d/ directory and see the sizes of the base, updates, and extras repository. Also, I suggest your to try to follow the instructions again from the beginning…
Humm…
Be careful, some basic packages will be deleted with those steps of SSH service…
Regards
Hello,
Thanks for the instructions. It did seem easy enough to follow and worked well until:
Google then took me to either irrelevant or highly complex and problematic pages… I’m going to revert my snapshot for maybe another try later.
Uninstall dnf from the centos7 install before starting. Centos7 dnf uses python2, when following the process above the installation of dnf in order should pull a python3 version for you.
Hi,
I followed the procedure but at this stage:
I’m getting the error:
My kernel version after running command
uname -r
:Any idea appreciated.
@Cyrus,
To fix this problem you need to boot into rescue mode, then remove the existing linux-firmware package and then manually download and install kernel, kernel-core, and kernel-modules, linux-firmware using rpm -ivh kernel* command.
After that reboot the machine…
@Ravi Saive,
Works with that long sequence. I am somehow able to
rpm -ivh kernel-modules
after removing a lot of packages related to python3 maybe. Able to show and boot into Centos 8. But since I was deep with a lot of packages in CentOs 7, after doing a lot of dnf removal.I ended up missing some crucial utilities after booting into CentOS 8. Ended up just reinstalling a CentOS 8. Was never able to run:
@John,
Sorry for the trouble, but I think you can install those missing utilities with dnf tool after booting into CentOS 8…