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 https://www.getpagespeed.com/files/centos6-eol.repo --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.

[upgrade]
name=upgrade
baseurl=http://buildlogs.centos.org/centos/6/upg/x86_64/
enabled=1
gpgcheck=0


Install (and reinstall) the following packages.

# yum erase openscap -y
# yum install https://buildlogs.centos.org/centos/6/upg/x86_64/Packages/openscap-1.0.8-1.0.1.el6.centos.x86_64.rpm -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 http://mirror.centos.org/centos/7/os/x86_64/RPM-GPG-KEY-CentOS-7

 

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=http://vault.centos.org/7.0.1406/os/x86_64/

 

 


........

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: libpcre.so.0: cannot open shared object file: No such file or directory

 


Simply run the following command to fix it:

 

# ln -s /lib64/libpcre.so.1 /lib64/libpcre.so.0


Additionally, run the following command:

 

# ln -s /usr/lib64/libsasl2.so.3.0.0 /usr/lib64/libsasl2.so.2


Then verify CentOS version using the following command:

 

# cat /etc/redhat-release

CentOS Linux release 7.0.1406 (Core)

 


This should be it!

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