Or will just be for trying to install some group of packages and if some error happens immediatly revert?
No. It uses the normal tools available through Monticello, but provides a convenient interface. Furthermore it runs some additional code to keep the image in a clean state. For example it ensures that every working copy has an repository assigned, that repositories pointing to the same physical location are of the same instance, that unused repositories get removed again, that categories are properly ordered, that unload operations do not leave empty categories and protocols, etc.
I always tough that monticello have complete control over the packages installed and unloaded from an image. I also assumed that it cleaned its mess after each operation. It is good to know this. But, a question, shouldn't this be part of Monticello. Or monticello fixed so to not leave dirty images behind it. Well that is just a comment. I know that there are alread a dozen monticello versions. :)
This is not only the fault of Monticello. Some of the problems (duplicated or missing repositories, wrongly ordered categories) only arise when you want to load multiple packages. Lukas -- Lukas Renggli http://www.lukas-renggli.ch