Upgrade from Cent. OS 6. 5 to Cent. OS 7 using redhat upgrade tool. Last month Red Hat released RHEL 7 and few days ago Cent. OS announced the GA of Cent. Uninstall a package using yum remove. To remove a package along with all its dependencies, use yum remove package as. Here is a full guide on how to install phpIPAM on CentOS 7. This should work on all RHEL based distributuons. For this guide I used competely fresh install of CentOS. Centos Install Packages Via Yum Command List' title='Centos Install Packages Via Yum Command List' />Build CentOS Machine. Build a CentOS 6. The CentOS install only needs to include the base packages through a. OS 7. As you may know, starting RHEL 7 Red Hat introduces support for upgrading to major releases RHEL 6. RHEL 7 via a tool called redhat upgrade tool. Not sure if this is 1. Cent. OS at this time, but I found the Cent. OS rpm packages on their development site and thought of giving them a try and luckily it turned out OK. Of course this is only a proof of concept, it may possibly not work by default on production environments, so use with care. For my test I used a fully updated base installation of Cent. OS 6. 5 VM running on Virtual. Box. Download required packagesmkdir p rootupgrade. Packagespreupgrade assistant 1. Packagespreupgrade assistant contents 0. Packagespreupgrade assistant ui 1. Packagesredhat upgrade tool 0. Install preupgrade assistantyum localinstall preupgrade assistant Run preupgrade assistantpreupg This does a check on the installed system and tries to identify potential issues after the upgrade. It should be run until all tests pass successfully. Active Session Limit Windows 2008 Support. Not sure it did anything on my VM as all tests returned not applicable. I havent used the original tool for RHEL7 but I suspect the Cent. OS equivalent is still work in progress, so I decided to skip it. More info on the preupgrade assistant is available in the Red. Hat official documentation. Install redhat upgrade toolyum localinstall redhat upgrade tool 0. Import the Cent. OS 7 rpm gpg keyrpm import http ftp. RPM GPG KEY Cent. OS 7. Run the upgrade tool. The tool can use a local ISO, the local media drive or a network URL to perform the upgrade. The network command argument needs to be followed by a release version rawhide is also supported and a valid installation repository at the time of this writing not all repositories were updated or reachable, so I did some trial and error until I found a working repo which can be defined as a standard URL or a mirror full mirror list is available here. Should this warn you that you didnt run the upgrade assistant, you can force its execution by adding the extra option redhat upgrade tool network 7. A successful run ends with this message Finished. Reboot to start upgrade. Reboot. After restarting the machine, the OS will boot a new grub entry called System Upgrade which is supposed to upgrade all packages previously downloaded by the upgrade tool. I ran into a small problem here Database environment version mismatch likely caused by the rpm tool itself rpm version is 4. Cent. OS 7 and 4. Cent. OS 6. cd mntvarlibrpm. Removing the rpm database files and rebooting worked for me CTRLD or exiting the shell should also work as that would exit the emergency mode and continue from the last step before the error occurred and the upgrade went through without other issues. Cent. OS Linux release 7. CoreUPDATEIf you follow this guide make sure you use the latest releases of the upgrade packages preupgrade assistant and redhat upgrade tool as provided by Cent. OS here. Also note that after the writing of this article, Cent. OS published a wiki page on the upgrade tool so its probably best to use that instead.