[Sussex] Activating Red Hat Enterprise Linux

[Nico Kadel-Garcia]

Jon Fautley wrote:
> On Thu, 11 Oct 2007 19:40:26 +0100
> "Nico Kadel-Garcia" <nkadel at gmail.com> wrote:
>
>   
>> On 10/11/07, Jon Fautley <jfautley at redhat.com> wrote:
>>     
>>> On Thu, 11 Oct 2007 13:36:34 +0100
>>> Brendan Whelan <b_whelan at mistral.co.uk> wrote:
>>>
>>>       
>>>> We ordered a RedHat Enterprise Linux license with an HP server
>>>> but it it taking weeks to get the actual number. I therefore
>>>> installed RHEL 5 on a server without using the installation
>>>> number and have how obtained an evaluation number. Does any one
>>>> know how I enter the number into the system? Thanks, Brendan
>>>>         
>>> Enter the activation code on the RHN website. Details should have
>>> been provided when you got the eval code. Then use rhn_register to
>>> register the system using your RHN account details.
>>>
>>> You could also raise a support case, and hassle HP to get your
>>> activation code over to you ;)
>>>       
>> Yould also use CentOS in the short term, and switch over when the
>> license is available. I've got tools for exactly that purpose if you
>> want them.
>>     
>
> I'd be interested to see how that works.
>
> Firstly, a bit of background...
>
> The "CentOS is RHEL" thing is a little misleading. You need to remember
> that one of the really important parts of how a distribution is built
> is the toolchain and build environment used to physically build the
> packages.
>   
Oh, my. Yes, this is completely agreed. From experience, the similarity 
is extremely good, enough that it's only when related tools do 
optimizations like "check for the version of redhat-release to select 
which options to use" that you get into trouble.

> CentOS have a different build environment to Red Hat (because ours is a
> custom-developed, in house solution). As such, I do not believe that
> CentOS can claim "100% Binary Compatibility" with RHEL. Sure, they use
> the same packages (and make a few tweaks), but in terms of how the
> packages are built, that's a whole different story.
>
> (if you want to see how much difference a different toolchain can make,
> I'm sure there's plenty of Gentoo ricers^Wusers that will be able to
> explain it to you ;)
>   
Been there, done that, have the T-shirt. Yes indeedy, this is true: it's 
particularly an issue with CPAN modules, and stuff compiled locally to 
replace the built-in RPM versions. (I've had tremendous issues dealing 
with software written in mod_perl 1.26 on an CentOS 4 system, with 
locally compiled Apache *and* a locally compiled Perl! It got.... pretty 
odd on that system.)
> So...
>
> This leads onto a bigger question - how do your 'migration tools' work?
> If it's just a case of swapping out redhat-release, and installing
> up2date/yum then this isn't going to wash with our support teams, I'm
> afraid. You would need to reinstall *each and every package* on your
> system to move from CentOS to a supported RHEL configuration. Sure, you
> might have a CentOS 'apache' RPM on your system, that's built from
> exactly the same source RPM as the RHEL version, but this is not going
> to be supported by Red Hat because it's been rebuilt. Sorry :(
>   
Ahh. I do an rsync download of an entire local RHEL mirror (assembled 
from installation CD's), make sure to install the critical 
redhat-release and RedHat registration tools and yum software (which 
takes work for RHEL 4, since it doesn't include yum and I have to grab 
yum and sqlite from RPMforge or a local repository), then replace every 
single component of /var/log/rpmpkgs with the "rpm -U --replacepkgs" 
command. Then I use tools like "yum list extras" to identify packages 
that have to be switched over and are not automatically over, and use 
tools like "for name in `rpm -qa`; do echo on $name: rpm -qi | grep 
'Build Host' | awk '{print $NF}'`; done" to get a list of build hosts 
that are *not redhat.com, and make sure those packages get removed or 
transferred to RHEL versions. It takes a bit of work, and it would be 
easier if the yum plugins for RHEL were more yum standards compliant. 
And it would be a *lot* easier if RHEL had easier ways to actually make 
a yum mirror repository of updates.

The only one it breaks on is "nss", which can be forcefully deleted and 
re-installed without too much pain.
> Just to explain my position, and where this email is coming from. This
> is not a dig at anyone that wishes to use CentOS over RHEL, or wants to
> migrate from one to the other (it's a damn sight easier to migrate to
> CentOS from RHEL than the other way around).
>   
Amen. Getting away from the DRM of RedHat package management tools since 
RHEL came out makes a lot of things easier. You do give up on the 
commercial support, and the ability to influence where RedHat is going 
as a customer.

> Oh, and for any of the conspiracy theorists kicking around, this isn't
> a dig at CentOS either. We love you guys :)
>   
Me, too. I've done several Beowulf clusters this way, and it's 
wonderful. I've actually *sent* RedHat copies of my tools for doing this.