Blame Manuals/Concepts/release.texi

076f77
The upstream vendor has released 4 versions of enterprise Linux that
076f77
CentOS rebuilds the freely available SRPMS for. So, the major CentOS
076f77
releases are CentOS 2, CentOS 3, CentOS 4 and CentOS 5.  The upstream
076f77
vendor releases security updates as required by circumstances. CentOS
076f77
releases rebuilds of security updates as soon as possible. Usually
076f77
within 24 hours (our stated goal is with 72 hours, but we are usually
076f77
much faster).
076f77
076f77
The upstream vendor also releases numbered update sets for Version 3,
076f77
Version 4 and Version 5 of their product (Currently EL 3 update 9, EL
076f77
4 update 6 and EL 5 update 1) 2 to 4 times per year. There are new
076f77
ISOs from the upstream vendor provided for these update sets. Update
076f77
sets will be completed as soon as possible after the vendor releases
076f77
their version ... generally within 2 weeks. CentOS follows these
076f77
conventions as well, so CentOS 3.9 correlates with EL 3 update 9 and
076f77
CentOS 4.6 correlates with EL 4 update 6, CentOS 5.1 correlates to EL
076f77
5 update 1, etc.
076f77
076f77
One thing some people have problems understanding is that if you have
076f77
any CentOS-3 product and update it, you will be updated to the latest
076f77
CentOS-3.x version.
076f77
076f77
The same is true for CentOS-4 and CentOS 5. If you update any CentOS-4
076f77
product, you will be updated to the latest CentOS-4.x version, or to
076f77
the latest CentOS 5.x version if you are updating a CentOS 5 system.
076f77
This is exactly the same behavior as the upstream product. Let's
076f77
assume that the latest EL4 product is update 6. If you install the
076f77
upstream original EL4 CDs (the ones before any update set) and upgrade
076f77
via their up2date, you will have latest update set installed (EL4
076f77
update 6 in our example). Since all updates within a major release
076f77
(CentOS 2, CentOS 3, CentOS 4, CentOS 5) always upgrade to the latest
076f77
version when updates are performed (thus mimicking upstream behavior),
076f77
only the latest version is maintained in each main tree on the CentOS
076f77
mirrors.
076f77
076f77
There is a CentOS Vault containing old CentOS trees. This vault is a
076f77
picture of the older tree when it was removed from the main tree, and
076f77
does not receive updates. It should only be used for reference. 
076f77