Hi, any idea if (when?) a new version of those RPMs with rollback included will become available for CentOS 4? Thanks, MaZe.
On Wed, 13 Jul 2005, Maciej �enczykowski wrote:
any idea if (when?) a new version of those RPMs with rollback included will become available for CentOS 4?
it scarcely matters -- rpm rollback is a essentially unattainable mirage, due to the unbounded nature of %pre and %post actions possible.
- Russ Herrold
On 7/13/05, R P Herrold herrold@owlriver.com wrote:
On Wed, 13 Jul 2005, Maciej ¯enczykowski wrote:
any idea if (when?) a new version of those RPMs with rollback included will become available for CentOS 4?
it scarcely matters -- rpm rollback is a essentially unattainable mirage, due to the unbounded nature of %pre and %post actions possible.
I wouldn't go that far (though obviously I understand the issues from the previous email). My goal with autorollback and a few patchs to the regular rollback code was to make it possible to rollback (automatically) a failed upgrade. That said scriptlets may in some cases need changing to work properly/intuitavily in a rollback transaction.
For the most part, because RedHat scriptlets are typically drop dead simple I do see any issues with their packages in a rollback. The way RedHat does scriptlets is really the best way to do them (that is as little as necessary), but sometimes you get a package from some other source (or maybe your own...we all have our reasons) that is a bit more complex. It is these complex scriptlets that need to take the possibility of a rollback into account.
So in short, I don't think rollback feature is that useless, but I really don't think it or the package universe it supports is completely there yet either.
Cheers...james
- Russ Herrold
CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
On Wed, 13 Jul 2005, James Olin Oden wrote:
On 7/13/05, R P Herrold herrold@owlriver.com wrote:
it scarcely matters -- rpm rollback is a essentially unattainable mirage, due to the unbounded nature of %pre and %post actions possible.
I wouldn't go that far (though obviously I understand the issues from the previous email). My goal with autorollback and a few patchs to the regular rollback code was to make it possible to rollback (automatically) a failed upgrade. That said scriptlets may in some cases need changing to work properly/intuitavily in a rollback transaction.
and within that limited scope, it may well work. I can easily think of the circumstance that is does not -- the 'upgradeany' transition from (RHEL|CentOS-)3 [2.4 kernel, modutils, and friends] to (RHEL|CentOS-)4 [2.6, etc] is a one way trip as to the general, used for a while install, case, in almost all circumstances.
In a narrow scope, with strong Change Management, and defined Sepcifications and Requirements, it should be possible to audit and stabilize the relevant scriptlets. Say I was rolling out 20k units in a telephony control application, ** without on-host end user level application services needed **, it could be done.
But in working through a cost-benefit analysis recently on a project of similar scale, I think I pretty throughly convinced the proponent of a 'rollback' approach, that I could automatedly rip out and re-provision and re-configure more consistently, cheaper, and quicker, than the 'rollback' based approach.
It is a fascinating area, JOO is well respected by me for his work in this field, and this topic has been hashed in more detail on the RH hosted rpm-list, and the Duke hosted rpm-devel mailing lists, for those intersted in more detail.
- Russ Herrold
On 7/13/05, Maciej Żenczykowski maze@cela.pl wrote:
Hi, any idea if (when?) a new version of those RPMs with rollback included will become available for CentOS 4? Thanks, MaZe.
If you mean plain jane standard "RPM Transactional Rollback" feature. It should be there, and has been there since somewhere in the RH 9/AS 2.1 days. If you mean autorollback, then I, and I do not speak for the CentOS developers, would not expect to see the latest autorollback code in any release of CentOS 4 as Centos 4 is based on RHEL 4 and errata for RPM in RedHat releases almost never occurs, and thus such an update is not likely to occur in CentOS 4.
Also, I would have to say as the person that wrote the autorollback code, that its not the right choice for most people. The code definately as far as I have seen can be safe in its inert state (i.e. you have not choosen to use it) but once you start trying to use it (or horrors a CentOS was distributed with it on by default) you have stepped into the zone of perferct configuration management. This especially true if you build packages that have complex opaque scriptlets, as you must really think through all the different ways in which your code could run. Also, as it is presently, there is no way to know if your scriptlet code is running in a "normal" upgrade or a "rollback" upgrade (where I work we have a one off patch that provides this but its truly heinous hack involving semaphore files). It doesn't mean this won't be added later, but beyond anything autorollback is an EXPERIMENTAL feature.
OK, did I scare you way? Well if not I would happily answer any questions on using it, take patches to improve it and so on, but I just felt the caveat emptor needed to be put out there.
Cheers...james
CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
OK, Thanks, I think you did manage to successfully scare me away :) Any comments on the progeny centos4 autorollback rpm rpms? Cheers, MaZe.
Their based on my set of patches for RHEL 3 rpm. It runs through my test harness and works fine as far as I have know. I have yet to use that particular set in a production environment because I'm still back on Centos 3/RHEL 3.
Have you read my article, BTW:
http://www.linuxjournal.com/article/7034
It gives a good description of how to use the standard transactional rollback feature of rpm.
http://lee.k12.nc.us/~joden/misc/patches/rpm
Gives some info on autorollback.
I would love for you to test out rollback and autorollback, but I want your eyes wide open before deploying on production (this being a relative term of course) systems, understanding what the feature can and cannot do.
Cheers...james
On 7/13/05, Maciej Żenczykowski maze@cela.pl wrote:
OK, Thanks, I think you did manage to successfully scare me away :) Any comments on the progeny centos4 autorollback rpm rpms? Cheers, MaZe. _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Just did now - very nice article. Think I'll stick to normal rollback, with rsync and local repository backup :) I'm more familiar with the 'hard way of doing things' and don't have the time currently to invest in discovering the right way (sad ain't it? thankfully I've only had to backout of one upgrade of squid during the last few months...) Cheers, MaZe.
On Wed, 13 Jul 2005, James Olin Oden wrote:
Their based on my set of patches for RHEL 3 rpm. It runs through my
test harness and works fine as far as I have know. I have yet to use that particular set in a production environment because I'm still back on Centos 3/RHEL 3.
Have you read my article, BTW:
http://www.linuxjournal.com/article/7034
It gives a good description of how to use the standard transactional rollback feature of rpm.
http://lee.k12.nc.us/~joden/misc/patches/rpm
Gives some info on autorollback.
I would love for you to test out rollback and autorollback, but I want your eyes wide open before deploying on production (this being a relative term of course) systems, understanding what the feature can and cannot do.
Cheers...james
On 7/13/05, Maciej Żenczykowski maze@cela.pl wrote:
OK, Thanks, I think you did manage to successfully scare me away :) Any comments on the progeny centos4 autorollback rpm rpms? Cheers, MaZe. _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
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James Olin Oden -
Maciej Żenczykowski -
R P Herrold