Migration from CentOS-5 to CentOS-6

1. Direct Upgrades Are Not Supported

An anaconda or yum upgrade is completely unsupported. See 6.0 Release Notes

Some users have managed an anaconda upgrade as discussed below. One way to migrate from CentOS-5 to CentOS-6 is the following:

1.1. Safest Migration

• Take and test a full backup of the old system.
• Bring up a second system with CentOS-6 either on new hardware, or on an alternate set of disks/partitions.
• Port over applications, data, and settings for users and the system from CentOS-5 to CentOS-6 looking for file and application syntax and operational differences.
• Look for /etc/*.rpm* configuration files backups left over from updates and compare old to current versions, adapting as required.
• Take down old system and move to new system.

• A forum user has posted their experience, as encountered by them, of issues when moving from CentOS 5.6 to 6.0 on the desktop

1.2. Riskier Migration

• Backup the system, as above.
• Do a fresh install of CentOS-6.
• Find out which applications work from old data.

1.3. Living on the Edge

Anaconda has an option which can be used to force the installer to recognize and try to upgrade an existing installation. This is the boot-time option upgradeany. Use it in the installer by interrupting the boot process, pressing the the <Tab> key to interrupt the boot process, and to edit the boot line to append that string at the end of the boot line.

Several known issues (not all of them !) when using this method to migrate from CentOS-5 to CentOS-6:

• The CentOS-5 centos-release has an epoch of 10 while the CentOS-6 version epoch has been intentionally reset to 0. This will result in centos-release and thus repo definitions and release version not being updated. This must be handled manually before or after the upgrade. See the Release Notes for the method.

• Package naming has changed for many packages so there may not be a direct equivalent. Examples, CentOS-5 -> CentOS-6:

  • yum-fastestmirror -> yum-plugin-fastestmirror

  • yum-priorities -> yum-plugin-priorities

  • Others ...

• The utility package-cleanup from yum-utilities can be used to help - see the man page. Useful switches include --orphans, --dupes, and --problems.

• The command: rpm -qa --last produces a list of packages in the order of installation and can be helpful in identifying old leftover packages, as can: rpm -qa | grep c5.

All in all, probably much more trouble than a fresh install and migration. There is of course no guarantee that the resulting system will not have hidden issues and instabilities. Once again, this path is unsupported.

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This page created and maintained by PhilSchaffner. Other Wiki contributors are invited to make corrections, additions, or modifications.