On Mon, 2005-08-22 at 11:01 +0900, Dave Gutteridge wrote:
> Thank you for your assistance.
>
> However, I must say that, as a newbie, I find your comments about CentOS
> being inappropriate for some kinds of application a little odd. Why
> should an application built for Linux not work on a distribution of Linux?
>
Now, here is a misconception.
Items designed for Windows 95 don't always work on Windows XP or Windows
2003 server.
Items built for Mandriva might not work on Redhat. Items built for
CentOS-3 might not work on CentOS-4.
Linux is really just the kernel ... a distribution contains many things
on top of the linux kernel.
Things like shared libraries (shared system files that all other
packages use to run ... very similar to system .dll files in Windows)
Shared libraries usually in /lib, /usr/lib, and /usr/local/lib. Some
shared libraries are in other places ... like the X stuff.
Certain RPM packages are compiled against a certain version of shared
libraries, and they may not (probably won't) work against other versions
(especially earlier versions, and maybe later versions too) of the
shared library.
If you upgrade shared libraries (like what happens if you upgrade KDE
from 3.3 to 3.4, or when installing other packages from outside the base
centos repos) then you might make some programs/packages in CentOS 4 no
longer function. (They might call functions that are removed or renamed
in newer shared libraries).
If you understand what shared libraries do, it might be possible to
change the affected programs (or the shared libraries) to get them to
work in both cases, but initially you will probably beak something ...
just like you would if you upgraded a bunch of DLL files on Windows NT
3.51 server to Windows 2003 Server.
> In any case, I searched around for which build would be most appropriate
> for me, and nowhere did I come across information that clearly said to
> me "You really can't or shouldn't run this kind of software on this
> build". Different distributions came with different philosophies,
> prices, and advantages.
But, because of the release cycle and support lifetime, some
distributions are better able to support certain things. Multimedia
editing, for example, is going to require always upgrading your platform
to newer versions of X, KDE, GNOME. CentOS does not do that within a
release. Gentoo, on the other hand, doesn't really upgrade at all. You
install it once ... and you upgrade forever when a new package comes
out. If Gnome 2.10 is considered stable, it can be installed (and you
can rebuild any other programs that need the new shared libraries). It
is always a moving target where you can get the latest and greatest
software.
I split this off to answer it separately ...
> But if any one of them could not run a Linux
> application, then isn't that build broken?
No, not at all. Linux is the kernel ... there are 2.0, 2.2, 2.4 and 2.6
kernels, and many things are supported in one of those and not in the
others.
----------------
CentOS is an Enterprise class distribution. That means it is designed
to be stable, but not necessarily have all the latest and greatest
features. Major versions are released on long (12-18 month) cycles
(instead of 6 month cycles for non-enterprise distros). The support
lifetime is 7 years (instead of 1-2 years for non-enterprise
distros) ... CentOS-2 has some very old packages that still get security
updates, but that are not going to be upgraded (like apache 1.3.x,
XFree86 4.1.x, gnome 1.4.x, kde 2.2.x, etc.). If you were to try and
install k3b (that requires at least kde 3.2 libraries) you will break
everything that comes with CentOS-2 and needs the KDE 2.2 libraries and
that was all built to work together.
For the major items, CentOS is never going to upgrade. For example
CentOS-3 has Gnome 2.2.x and KDE 3.1.x ... it will stay gnome 2.2.x and
KDE 3.1.x until it retires in 2010. If something was released in gnome
2.8.x, it is not going to be available for CentOS-3 without taking a
risk that you will break compatibility with installed programs.
So, CentOS is designed to be installed and provide what it provides ...
a long term, stable, enterprise distro with a long release cycle (about
18 months) and a long support cycle (7 years). By the time CentOS-5.x
is released (probably around September 2006), items in CentOS-3.x will
be very dated, items in CentOS-4.x will be fairly dated, and items in
CentOS-2.x will be prehistoric :)
But, if you installed an Application on a CentOS-2 server and you have
CentOS-2 installed on 500 workstations that need to use that
application, it will still work great until May 31, 2009 (when CentOS-2
goes away). You will be able to get updates for those workstations and
the server until that point ... although, you will not be able to burn
DVDs from them.
Hopefully this makes sense.
--
Johnny Hughes
<http://www.HughesJR.com/>
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