Upgrade from CENTOS6 to Centos7 step

1. Backup

2. Install dependency list

Yum source file/etc/yum.repos.d/upgrade.repo, content is

[Upgrade]name=upgradebaseurl=http://dev.centos.org/centos/6/upg/x86_64/ enabled=1gpgcheck=0

Install dependent packages

Yum Install preupgrade-assistant-contents redhat-upgrade-tool preupgrade-assistant

3. Verifying the Upgrade

Execute the command you just installed

Preupg

Importing Yum's GPG key

RPM--import http://mirror.centos.org/centos/rpm-gpg-key-centos-7

4. Start the upgrade

To perform an upgrade command

7 --instrepo=http://mirror.centos.org/centos/7/os/x86_64

If an error is encountered

Error:database disk image is malformed

Clear Cache, Retry again

Yum Clean Dbcache

5. Restart

Reboot

Upgrade from CENTOS6 to Centos7 step