[CentOS-docs] HowTos/MigrationGuide

[Phil Schaffner]

On Mon, 2007-03-26 at 19:13 +0200, Andreas Rogge wrote:
> Hello Phil,
> 
> shouldn't we add something like "Before doing the Migration please 
> upgrade to the most recent release". This would probably help to support
> issues that arise from the migration itself, as we have a "known good" 
> base from where the migration is done (I know, you should always run the 
> latest release. But I'd explicitly mention it again).

Agreed.

> Maybe upstream will fix at least some of the migration issues in the 
> next update spin - at least if we tell them what issues are there.

Maybe, but people with RHEL entitlements need to be involved if they're
going to pay much attention.  At least I've been asked to replicate
problems reported in RH BZ on EL - otherwise they may write it off as
CentOS issues.

> I know we don't support these migrations at all, but it would be great 
> if there was a "Issues you'll probably run into"-section concerning 
> problems that arise when you use "software X" and migrate. Like Gnome's 
> usersettings, migration of evolution and firefox profiles, etc.

The Wiki structure proposed can certainly accommodate as much content of
this type as people are willing to provide.

> We could also add a list of packages that makes CentOS 5 "compatible" to 
> CentOS 4 binaries?
> There are compat-packages, but most people just think "why the hell did 
> my software break? I know there a dependencies in RPM, but I also know 
> that many people are running binary 3rd-party software and stuff dropped 
> in /usr/local and /opt which is not managed with RPM.

Don't know quite how to handle the compat issues other than suggesting
that installing the packages might help, and recommending against
installing non-RPM non ELx packages on an ELx system.  Perhaps
developers or others can comment on this.

> Some of these programs will probably stop working (glibc, libstdc++, 
> ...), so we should provide information how to make a CentOS n+1 system 
> as compatible as possible to CentOS n. Maybe with a list like "if you 
> still want to run X you have to install Y" or maybe just "install 
> compat-* we don't care".
> And we should probably also mention issues where you already use 
> compat-libs on CentOS 4 and what will happen to them on an upgrade (I 
> guess they'll stay in place, but in fact I don't have any idea what the 
> upgrade-code will do)

Me neither.  My approach has been to update or get rid of all old
packages, but some people with legacy apps may not be able to do this.
virtualization may be a better answer for some. VMware Server is a good
option to run older packages without compromising the new system.

> Regards,
> Andreas Rogge

Thanks for the comments.  Now if I can just find time to do some more
editing.

Regards,
Phil