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Old 10-03-2008, 11:55 PM
"William L. Maltby"
 
Default Putting CentOS 5.2 kernel on CentOS 4.x

On Fri, 2008-10-03 at 16:21 -0700, Scott Silva wrote:
> on 10-3-2008 2:48 PM Fong Vang spake the following:
> > Has anyone tried to install a CentOS 5.x kernel on a CentOS 4.x system?
> > Is this doable? I"m aware of the dependencies but I'm curious if anyone
> > has done this successfully.
> >
> > Basically, we have a few hundred 4.x systems that cannot be upgraded to
> > 5.x, yet, but we do need the kernel update to fix the XFS problem as
> > described here: http://bugs.centos.org/view.php?id=3125
> >
> You would be on your own with that! Do you have a non-critical system you can
> test on? You would probably need to get the source rpm and build it on a 4.x
> devel system.

Hmmm... Reaching through the half-heimers-fogged brain...

ISTR that the critical item is the APIs (binary compat) provided by
glibc. If so, the glibc-2.5-24.i686 on 5.2 and the 2.3.4-2.41 are
probably different enough that binary compatibility would be broken.

Further, compiling the recent kernel on 4.x might be also difficult
because the source compatibility might be broken (although not certain)
due to parameter changes introduced in the newer kernel version.

But, that's a whole bunch of "ifs" that may be worth investigating,
depending on available time, resources and time constraints.

If one does get a clean compile and no apps break, very fortunate. If
the source must be changed, be sure to maintain diffs that can be
applied when new versions with critical fixes (like security) appear.

Overall, my personal bias would be to avoid the whole scenario.

> <snip sig stuff>

If any of my above is FUD, please forgive. It's hard to recall so much
from so long ago.

--
Bill

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http://lists.centos.org/mailman/listinfo/centos
 
Old 10-04-2008, 12:39 AM
"Fong Vang"
 
Default Putting CentOS 5.2 kernel on CentOS 4.x

So you're saying that the CentOS 4.x system is married with the 2.6.9 kernel?* Maybe the packaging of the kernel RPM is different between 4.x and 5.x, but why would a 5.x kernel not work on a 4.x system, especially considering you can always download the latest kernel from the kernel source tree and run that so this doesn't sound right.


I just need the later kernel, not the new glibc which will break compatibility.

On Fri, Oct 3, 2008 at 4:55 PM, William L. Maltby <CentOS4Bill@triad.rr.com> wrote:



On Fri, 2008-10-03 at 16:21 -0700, Scott Silva wrote:

> on 10-3-2008 2:48 PM Fong Vang spake the following:

> > Has anyone tried to install a CentOS 5.x kernel on a CentOS 4.x system?

> > Is this doable? *I"m aware of the dependencies but I'm curious if anyone

> > has done this successfully.

> >

> > Basically, we have a few hundred 4.x systems that cannot be upgraded to

> > 5.x, yet, but we do need the kernel update to fix the XFS problem as

> > described here: http://bugs.centos.org/view.php?id=3125

> >

> You would be on your own with that! Do you have a non-critical system you can

> test on? You would probably need to get the source rpm and build it on a 4.x

> devel system.



Hmmm... Reaching through the half-heimers-fogged brain...



ISTR that the critical item is the APIs (binary compat) provided by

glibc. If so, the glibc-2.5-24.i686 on 5.2 and the 2.3.4-2.41 are

probably different enough that binary compatibility would be broken.



Further, compiling the recent kernel on 4.x might be also difficult

because the source compatibility might be broken (although not certain)

due to parameter changes introduced in the newer kernel version.



But, that's a whole bunch of "ifs" that may be worth investigating,

depending on available time, resources and time constraints.



If one does get a clean compile and no apps break, very fortunate. If

the source must be changed, be sure to maintain diffs that can be

applied when new versions with critical fixes (like security) appear.



Overall, my personal bias would be to avoid the whole scenario.



> <snip sig stuff>



If any of my above is FUD, please forgive. It's hard to recall so much

from so long ago.



--

Bill



_______________________________________________

CentOS mailing list

CentOS@centos.org

http://lists.centos.org/mailman/listinfo/centos



_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 
Old 10-04-2008, 12:57 AM
"Bart Schaefer"
 
Default Putting CentOS 5.2 kernel on CentOS 4.x

On Fri, Oct 3, 2008 at 5:39 PM, Fong Vang <sudoyang@gmail.com> wrote:
> So you're saying that the CentOS 4.x system is married with the 2.6.9
> kernel? Maybe the packaging of the kernel RPM is different between 4.x and
> 5.x, but why would a 5.x kernel not work on a 4.x system, especially
> considering you can always download the latest kernel from the kernel source
> tree and run that so this doesn't sound right.

If system call interfaces have changed, you *can't* always download
and run the latest kernel from the kernel source tree. Sometimes
programs that make system calls have to be recompiled along with the
kernel. I haven't paid attention to whether there was any such change
introduced frm 2.6.9 to 2.6.18; I'd sort of expect a bigger change in
the version number if so.

Aside from the binary compatibility issue. though, occasionally things
like the layout of /proc and /dev change in incompatible ways. The
introduction of udev between CentOS 3 and 4 makes it seriously
problematic to run a CentOS 4 or 5 kernel on a CentOS 3 system, for
example. You may have to install more than just the kernel.
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Old 10-04-2008, 10:50 AM
"William L. Maltby"
 
Default Putting CentOS 5.2 kernel on CentOS 4.x

Please, take the time to intersperse your replies. Top-posting makes it
harder to follow.

On Fri, 2008-10-03 at 17:39 -0700, Fong Vang wrote:
> So you're saying that the CentOS 4.x system is married with the 2.6.9
> kernel?

No.

> Maybe the packaging of the kernel RPM is different between 4.x and
> 5.x, but why would a 5.x kernel not work on a 4.x system, especially
> considering you can always download the latest kernel from the kernel
> source tree and run that so this doesn't sound right.

I don't believe rpm packaging is an issue. As long as prerequisites are
satisfied, rpm would do its thing.

Anything is possible. And may even be easy. The CentOS wiki has a page
on making your own kernel. *Usually* this is done within the same major
branch, for good reasons. Often it is just to enable some feature which
is disabled by default by upstream. Within the same major kernel
version, this is often no problem as efforts have been made to avoid
breaking ABI by the glibc and kernel folks.

Expand your consideration to a system view. Kernel provides basic
functions and management. To use these, system calls are used. These
have required parameters. They must have the right attributes, order,
etc. Most of these interfaces are provided through a set of libraries,
glibc being the predominate one, that provide an Application Binary
Interface (ABI) made to match a major kernel version. This does
insulate, to some degree, the applications from changes in the
underlying kernel. Applications can make the system calls directly and,
thus, are not insulated if they do so. If if that is not done, there are
limits. If the kernel changes are too great, relative to the specific
version of glibc and other libraries, the binary interface may be broken
in certain areas.

If you upgrade the glibc (and any other needed libraries - might be only
a few, I don't know) to support the kernel, then the applications may
need to be recompiled to use the new libraries. And other libraries that
depend on glibc, and other apps/libs that depend on those, and other ...

None of this is certain. In C (and C++) which, IIRC, is the language
used, there are techniques that can allow for certain types of
mismatches. But this does take more code.

>
> I just need the later kernel, not the new glibc which will break
> compatibility.

Like the other person said, give it a shot. But as he said, use a test
system.

Last, consider the following. System maintenance. As upgrades occur in
the kernel and/or libraries and applications, you may have a maintenance
nightmare. One very small change in any of the components may render
your system unreliable or even not runnable. You may have to maintain
many sources yourself. Even 1 source may be tough. Automatic updates may
not be at all feasible. You may miss, or be unable to install, critical
security updates or fixes without great effort.

Summary in "real world" terms: you can't stick the pistons, conn rods,
intake manifold, ... from a 1966 Pontiac GTO (389 c.i., tri-power, ...)
in a Ford 302 very easily. :-(

So, just proceed with caution, consider long-term impact and how smart
or dumb you might appear to those who matter later on.

If the later kernel is your *primary* factor, build (beg, borrow, steal)
a system around it.

> <snip>

--
Bill

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