On Tue, Feb 25, 2014 at 10:25 AM, Styma, Robert E (Robert) robert.styma@alcatel-lucent.com wrote:
I recently built a CentOS 6 system as my main machine at home. With a bit of help from members of this list, it is now working better than the machine it replaced (RIP). The new machine works so well, that I would like to convert some CentOS 5 machines to CentOS6.
I did some research on the web and the new install is still considered the proper way to upgrade CentOS. Same as Fedora and RHEL. The question becomes, "What makes the Ubuntu developers so clever that they can do major upgrades through their apt based update system?"
There must be some sort of gotcha or tradeoff involved in allowing this.
Does anyone have any insights on why they can get away with this while CentOS cannot?
First, CentOS does exactly what RHEL does, so this is not really a CentOS question.
The tradeoff is that Ubuntu doesn't go to the effort to ensure that for 7+ years you can do updates and not have anything that was previously working break because a change from the update. RHEL/CentOS may not be perfect at this, but breakage is very, very rare because the updates are mostly backported security/bug fixes that don't change behavior. Ubuntu does more frequent updates of the included package versions (even with their LTS version) and if a package changes behavior that is left as your problem. By the time RHEL does it's next major release, you have a many-year jump in the underlying package versions with enough changes that even if you could do an automated update it would probably be a bad idea (there may be things as drastic as new filesytem choices, etc.). A fresh install of CentOS isn't difficult and you should have a plan to backup/restore your own data anyway, so once you get used to the timing it works out pretty well to match up major releases with replacing hardware and/or general cleaning up of your own applications and data.