How to upgrade CentOS 6 to CentOS 7

Use the CentOS Vault repository:

Since CentOS 6 is EOL we need to point our yum to the vault repo, for this we run the following command:


# curl --output /etc/yum.repos.d/CentOS-Base.repo

Installing Redhat upgrade tool:

redhat-upgrade-tool is not available on standard repositories, you must setup the repository to install it.

# vi /etc/yum.repos.d/upgrade.repo

Place the following entries in it.


Install (and reinstall) the following packages.

# yum erase openscap -y
# yum install -y
# yum install redhat-upgrade-tool preupgrade-assistant-contentsyum install redhat-upgrade-tool preupgrade-assistant-contents -y


PreUpgrade Assistant:

Run the following command to check the potential problem you might encounter with an upgrade from CentOS 6 to CentOS 7 before making a changes to the system.

# preupg


From the output of the previous command you can find what packages will be affected by this upgrade.

Perform the actual upgrade:

We are going to use the repo file for the upgrade, issue the following command to import the GPG key:

# rpm --import


As per the man page, the following command is used to upgrade CentOS 6; this will download the necessary packages from the internet:


# centos-upgrade-tool-cli --network=7 --force --instrepo=




setting up system for upgrade
Finished. Reboot to start upgrade.

Now reboot the server.

# reboot

Upgrade to CentOS 7:

The server will boot with the redhat-upgrade-tool kernel to upgrade the CentOS 6, now you can find the upgrade progress/activity via console.


Upgrade  from CentOS 6 to CentOS 7 - Upgrading the Packages


Now you can see the installation of the packages.

READ  Configure iSCSI Target & Initiator on CentOS 7 / RHEL7

Upgrade  from CentOS 6 to CentOS 7 - Upgrading the Packages


Once completed, you will get the login screen.


Upgrade  from CentOS 6 to CentOS 7 - Login

Some times after the reboot you might get an error like this:


grep: error while loading shared libraries: cannot open shared object file: No such file or directory


Simply run the following command to fix it:


# ln -s /lib64/ /lib64/

Additionally, run the following command:


# ln -s /usr/lib64/ /usr/lib64/

Then verify CentOS version using the following command:


# cat /etc/redhat-release

CentOS Linux release 7.0.1406 (Core)


This should be it!

  • upgrade centos, centos 6, centos 7
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