OLPC-Update + RPMs WAS:Re: OLPC XO Opera browser as Sugar activity

[Erik Garrison]

On Fri, Jun 27, 2008 at 12:17:57PM -0700, david at lang.hm wrote:
> On Fri, 27 Jun 2008, Erik Garrison wrote:
>
>> We should move away from using olpc-update to upgrade systems.  We
>> should not implement this or any hack to preserve manually installed
>> rpms through olpc-updates.
>>
>> Existing package managers (e.g. apt, rpm) do exactly what we want and
>> more.  Furthermore they are extensively tested and well documented.  Why
>> have we locally manufactured and promoted the square wheels of
>> olpc-update and copy-nand?
>
> every existing package management system makes assumptions about how 
> large an upgrade you are making. even apt (historicly one of the best 
> long-term systems) runs into significant problems if the upgrade that you 
> are making is too large, frequently without being able to identify the 
> problem ahead of time.
>
> with yum, can you (in one step) do an upgrade from Fedora 7 to Fedora 9? 
> I don't think it can.
>

It can't be done in one step, but people use yum for distribution
upgrades already:
http://www.howtoforge.com/upgrading-fedora7-desktop-to-fedora8

Recently I have been completing my Ubuntu distribution-level upgrades in
one step.  So we should know that it is possible that such upgrades can
happen within the scope of a package manager.

> the snapshot based approach has headaches, but the one huge advantage 
> that it does have is the ability to do the upgrade no matter what the 
> condition of the old system image is (including the possibility that the 
> system image is corrupt)
>

IMO, the snapshot approach has headaches for everything *but*
distribution upgrades.  How, for instance, do we issue security updates?
How do we push small bugfixes?  This is problematic for developers,
users, and particularly the support staff which have to sheperd users
through monolithic upgrade processes.

Despite any apparent vitriol to the contrary, I am not suggesting we get
rid of snapshot based upgrades.  They can obviously coexist with a
well-maintained package management system vector for upgrades.  It will
always remain a useful sledgehammer.  However, if we wish to preserve
custom packages across such upgrades I suggest we can use a system such
as yum rather than hacking olpc-update to play nice with the packages.
Evidence strongly suggests that this is possible.

What functionality do we certainly lose by using a package management
system as our default software distribution system?

Erik