The product which doesn't exist?
If they buy your hackneyed product then learn their mistake, they are going to be very unimpressed with you.
The product exists. I am adding a new feature to the Linux version of the product. I am doing a Linux version of patch management. I had been trying to figure out rollbacks and thought somebody could offer advice.
We have been, for pages. I'll summarize, one more time:
You can advise and warn, but DON'T try to be "smart" and upgrade/downgrade/override things for your users. You will cause damage and pay dearly for this if you try.
Either
1) roll back your own software, and nothing but, or
2) do it right, rolling back EVERYTHING with full backups and the like.
The Windows version of the app does patch management as one of its functions. I am required to implement an equivalent functionality for Linux systems. I have succeeded in gathering patch related data with several popular distributions, and also doing an automated patch install similar to the one the Windows product does. Perhaps, as you say, there is no safe Linux equivalent for rollbacks.
It's an apples to oranges comparison. You're also trying to implement across all UNIX something which you only did on one OS.
I'm wondering why you're refusing to even consider proper backups as a method...
Brandon9000,
Linux does not do patches the way windows does. It uses packages. Some versions even use deltas, but the crux of it is, you cannot do what you are trying to. It is a one way proposition. The only way to avoid that is to try to claim all updates they make to any configuration files owned by a package and store them in some sort of repository linked to the version they are associated with.
You will then have to uninstall the package, install the new package (old version or new version) and then apply the config file for that version, because configuration files sometimes change formats.
LINUX IS NOT WINDOWS BUT FREE. It is an entirely different OS with different structures. EVERYTHING in LINUX is a file. Windows is very different. Is Windows POSIX compliant? Can Windows change kernels on a running OS with a splice? Does Windows have initial ram disks?
What you want are ways to save machine states, but that is an all or nothing proposition.
Might it be possible to do what you want? Sure, but it will take a very clever person a lot of time, and even more code to do it, and even in those cases, they will probably find a corner case that will bite them on the ass so hard, they will bleed money.
I believe that is a correct analysis. My mandate is really not to spend weeks on a single feature, or at least very rarely. They want me to scratch items off my "to do" list and move on. The thing that makes me rather timid about doing anything too creative for rollback is that a customer may apply it to a core pieces of software where the cost of messing up is very high.
As for backups, that sounds like something where I would have to make some assumptions about the box the product finds itself on, and, in general, our customers run the gamut of different environments. Perhaps I misunderstand.
This sounds like the perfect opportunity to build in backup features and sell them an add on product.