On Thu, Jul 25, 2013 at 5:28 AM, Tom H <[log in to unmask]> wrote:
> On Thu, Jul 25, 2013 at 1:28 AM, David G.Miller <[log in to unmask]> wrote:

>> I'm guessing you could back-port FedUp to EL and have a reasonable shot at
>> upgrading EL-n to EL-n+1. I wouldn't want to guarantee that an arbitrarily
>> complex installation will work though and the people who really want to
>> upgrade are those with really complex systems that they don't want to have
>> to re-create from a clean installation. So we end up stuck with the
>> contradiction that simple installations could probably be upgraded but the
>> complex installations that people really want to upgrade can't.
>
> If you package and script your configuration, there's no such thing as
> a complex system.

Your faith in the ability of scripting to read human minds seems to be
boundless. Mine.... is far lower.

For example, simply updating Subversion from one version to another is
irreversible: all the working copies checked out with Subversion 1.4
(from Scientific Linux 4) to Subversion 1.6.11 (the current copy in
Scientific Linux 6) get updated when used, and are no longer
compatible with the older Subversion 1.4 client. If you have a home
directory that will still be used with SL 4 operating systems in the
same work environment, it's a *big* problem. Similar problems occur
with locally compiled packages that were written to require versions
of Python or gcc that are no longer availalbe in the new OS. And you
would not *believe* the number of packages I've had to help rebundle
in the last 5 years because the authors were unable, or unwilling, to
et off Apache 1.3 and I had to help switch their base OS to something
still supported.