How To Upgrade Centos 6 to Centos 7

tutorial how to upgrade centos 6 to centos 7 the latest release of the CentOS operating system. redhat-upgrade-tool is not available on standard repositories, you must setup the repository to install it. Before upgrade centos 6 to Centos 7 continuing with the upgrade process, you must have a backup. Having a backup is very important because if anything goes wrong, you can restore from it and have your OS server working again.

here is CentOS 7 Major Changes

  • Following are the more notable changes are included in this release are:
  • Updated Kernel to 3.10.0
  • Added support for Linux Containers
  • Open VMware Tools & 3D graphics drivers out of the box
  • OpenJDK-7 as default JDK
  • Upgrade from 6.5 to 7.0 using preupg command
  • LVM-snapshots with ext4 and XFS
  • Switch to grub2, systemd and firewalld
  • Default XFS file system
  • iSCSI and FCoE in kernel space
  • Support for PTPv2
  • Support for 40G Ethernet Cards
  • Supports installations in UEFI (Unified Extensible Firmware Interface) Secure Boot form on compatible hardware

CentOS 7 Release Notes

Before you go for CentOS 7.0 after CentOS 6.x, I suggest you to consider following things, because many of things have been changed in this release.

  • grub is now replaced with grub2
  • init is now replaced with systemd
  • Difficultly in understanding and editing grub.conf (grub2)
  • Difficultly in understanding /etc/init.d
  • No more text log files for system log (journalctl instead)
  • No more ext4 filesystem, added XFS as default filesystem
  • CentOS 6.x will be supported until 2020

Installing prerequisites on your centos login as root
First, add the yum repository for developer software by creating the file /etc/yum.repos.d/upgrade.repo. Populate it with the following contents:

You can now install the required packages, preupgrade-assistant-contents, redhat-upgrade-too, and preupgrade-assistant:

Verifying upgrade
you can verify system if this is ready to upgrade to CentOS 7 using the preupgrade assistant tool. This tool will examine the current setup and confirm that it’s ready for an upgrade:

In this case, the result looked like this:

import the GPG key. We will be using the one from the CentOS team:

Now You can Starting the upgrade to centos 6
start the upgrade after importing the GPG key:

If you get the following error message:

Try executing the following command and try again:

last step Rebooting the server
CentOS is now initializing your server for upgrade. You will need to reboot the server so CentOS can upgrade the operating system, from CentOS 6 to CentOS 7:

You can monitor progress via the online console

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