On Fri, Jun 27, 2014 at 9:49 AM, Lamar Owen <[log in to unmask]> wrote:
> On 06/25/2014 07:42 PM, Nico Kadel-Garcia wrote:
>>
>> On Wed, Jun 25, 2014 at 1:13 PM, Lamar Owen <[log in to unmask]> wrote:
>>>
>>> Yes, it will work partially. To make the switchover complete you need to
>>> do a 'yum distro-sync full' afterwards. While I agree that a reinstall is
>>> cleaner, that isn't a direct answer to your question.
>>
>> You also have to re-install *every single package*, especially those
>> that may have minor, uncertain differences between the two
>> repositories. It can be done, I've done it between CentOS and RHEL and
>> back several times on the same environment.
>
>
> This is what 'yum distro-sync' is supposed to do (distro-sync full works
> based on the package checksums, and is supposed to reinstall every single
> package that has a different checksum than the currently pointed-to repos).
> If it does not do it properly, it's a bug that needs to be filed against the
> upstream yum.

Based on the tests I just did on SL 6.5, the "yum distro-sync" command
relies on package name, not checksums of the installed packages. I
have a local development repository for Samba and RT4 builds that I
do: I deleted and recompoiled the packages, and installed the rebuilt
packages of the same name in the yum repository.

Running "yum distro-sync" failed to detect any discrepancy and did not
re-install them.

>> It's a very expensive process in terms of system resources and local
>> bandwidth.
>
>
> It is that (In my case the new repos were on iSCSI SAN and the process,
> while still taking quite a while, completed smoothly on all three Altix
> systems on which I tried it).

Good. I think that to ensure complete switchover to CentOS, Scientific
Linux, or RHEL, you'll really need to do a "yum reinstall" on every
single package, not just rely on "yum distro-sync"