[CentOS] Moving the system from 5.3 to 5.4

[Brian Mathis]

On Tue, Jan 19, 2010 at 3:30 PM, Bowie Bailey <Bowie_Bailey at buc.com> wrote:
> John R Pierce wrote:
>> Renato Botelho wrote:
>>
>>> My question is not *how* to update, but how the rpm detects a
>>> new version is available and automatically update to rpms from
>>> 5.4 version.
>>>
>>>
>>
>> I believe it gets the updates from /5/  on the yum repos, not /5.x/
>> so when /5/ has rolled to be a link to /5.4/ instead of /5.3/, voila,
>> its getting the components from there.
>>
>
> Exactly.  The "5.3" and "5.4" versions are a just collection of
> updates.  When the updates that make up 5.4 are pushed out to the repos,
> you get updated to 5.4 on your next "yum update".
>
> --
> Bowie


To be more precise, any particular OS version (5.3, 5.4, etc...) is a
collection of packages.  Each package has its own version number that
is totally separate from the "OS" version.  All of the package version
information is stored in the RPM database, and the "yum" tool looks at
this database and compares package versions to those on the centos.org
servers.  If it finds packages that need updating, yum lists them as
having an update available.

An OS version is a snapshot of package versions that someone (redhat)
has decided to stick a version number onto.  So centos 5.3 is just as
list of packages at a certain version.  However, as soon as it is
released, any package might have an update to it.  OS versions tend to
have updates that make some bigger changes to the system, as opposed
to typical updates that are mainly security fixes.

The centos servers manage the OS versions by making a link from 5 ->
5.4, for example.  The files in /etc/yum.repos.d define how yum finds
the servers and updates.