[CentOS] Upgrading to CentOS 7

Johnny Hughes johnny at centos.org
Tue May 19 14:37:31 UTC 2015


On 05/19/2015 09:12 AM, Timothy Murphy wrote:
> Johnny Hughes wrote:
> 
>> On 05/19/2015 07:43 AM, Timothy Murphy wrote:
>>> I read in <http://wiki.centos.org/TipsAndTricks/CentOSUpgradeTool>
>>>
>>> "Warning: use of this tool is currently not recommended as several
>>> system- critical packages are of a higher version number in CentOS 6.6
>>> than they are in CentOS 7 so those do not get upgraded correctly. This
>>> renders yum and several other system tools non-functional."
>>>
>>> Does this still hold?
>>> It seems to me a bit pointless to offer a tool
>>> with the warning that it does not work.
> 
>> It is not pointless, some people want to do it.
>>
>> I would not use it.
> 
> First of all, thank you very much, Johnny, for all your work.
> You are doing a fantastic job.

Thank you.

> 
> However, I find your answer here a little odd.
> It's a bit like the surgeon saying, "I wouldn't have this operation,
> but if you want it just lie back."
> 
>> The best way to do any major update is to backup your data, install the
>> OS, bring back your data and make all the newer services (if you are
>> moving things like databases or web directories, etc.).
>>
>> Some people want to take shortcuts to this procedure, and with enough
>> effort, that tool can work.  But to me, there is too much effort and
>> there are too many older packages left around as clutter, so I would
>> never do it.
> 
> If it would take you a lot of time and effort to clean up after the upgrade
> I can't imagine how long it would take me.

It is going to take a long time to fix issues in any Major upgrade.
Most of your apache config files will not work, many times you need to
run an upgrade on database system schemas, maybe new LDAP schema's etc.

That in itself is hard.

Add on top of that, if using the update tool, a bunch of packages that
are running using the compat-glibc from the previous release.  You not
only have to figure out how to do all the updated stuff from above ..
you now have to figure out which of the cruft that exists from the
previous version (which is still on your system as there was no upgrade
for it, etc.) that is needed and what is not.

This problem is not unique to CentOS or even Linux.  Anyone ever upgrade
a domain controller from WinNT-4 to Windows Server 2000 .. or Server
2003 to Server 2008, etc.  Stuff never works like it is supposed to on
in-place upgrades.  You will be, IMHO, fighting problems for the
lifetime of that setup after that.  Much cleaner to upgrade without
cruft from the old OS.

> 
>> Red Hat released this, so we rebuilt it .. that does not mean one should
>> use it.
> 
> Strange.
> 

Not at all .. CentOS is a rebuild of RHEL source code.  I do not agree
with all the package selections they make.  If it were up to me, some
things would be newer or older in many releases .. but it is not up to
me.  If Red Hat releases the Source Code, we build it.

Thanks,
Johnny HUghes

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