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?
On Tue, Feb 25, 2014 at 10:25 AM, Styma, Robert E (Robert) <robert.styma at 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. -- Les Mikesell lesmikesell at gmail.com
On 02/25/2014 10:25 AM, Styma, Robert E (Robert) 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? >The reason is this ... You could work out a procedure to do an in place yum upgrade .. it would involve doing all kinds of stuff with python versions so that yum and the rpm database could live through the update. Even after you did this, most of your data would not be usable. Because .. In CentOS-5 to CentOS-6 look at php. You move from php-5.1.6 to php-5.3.3 ... almost none of the php websites would work after an upgrade. Same for things like mysql in CentOS-4 to CentOS-5, it went from version 4.1.22 to version 5.0.95. Lots of things required to do this upgrade to the actual data. So, if you upgrade in place, you get finished and you have a broken system until you figure out how to fix all of your data and config files .. and the difference is 3-4 years worth of in version numbers (unlike 6 months at most in a bleeding edge distro). Skip 2 versions (EL4 to EL6) and it is even more change (5-8 years of difference). Distros that upgrade in place BREAK your one system and it does not work until you figure it out. Also, not every package in the old system exists or has a replacement in the new system, so you have orphaned cruft left on your machines. If you upgrade onto another machine, you can do an install, move over your data and configs one by one, work out all the problems and get the fixes in, etc. You can move services one at a time, change pointers, never have downtime. If you upgrade i place, BAM .. down until you figure it all out. I guess other distros that upgrade in place don't care that you are left with a broken system. If you absolutely insist to upgrade in place ... boot the new DVD for the new version and at the command line do: linux upgradeany That will let you upgrade in place and end up with broken data/configs with things that do not start, etc .. just like the other distros who do in place upgrades. When it breaks (it will), then you get to keep all the pieces :) -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 198 bytes Desc: OpenPGP digital signature URL: <http://lists.centos.org/pipermail/centos/attachments/20140225/fcfabbb0/attachment-0002.sig>
> 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?To add to Les' points, Fedora has offered in place upgrade, going at least as far back as FC1 -> FC2. I seem to recall that I used to be able to upgrade my free RHL (non-enterprise) versions in place, as well, but I won't swear to it. -- Mike Burger http://www.bubbanfriends.org "It's always suicide-mission this, save-the-planet that. No one ever just stops by to say 'hi' anymore." --Colonel Jack O'Neill, SG1