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Just random notes at this point: - Razor is a package management system replacing rpm and yum. Razor implements management of packages installed on the system, dependency solving, and upgrading in a small compact code base with minimal dependencies. - Key points: one file format for package sets, specified and implemented by razor; no point in splitting dep-solver and package manager, there is too much implementation overlap. By hand coding the on-disk format we have a solid foundation on which to implementing fast dependency solving, error recovery etc. No complex dependencies in package management stack. In other words, package management is *simple*, no need to overdesign it. - Use one simple file format as the core of the system. The razor package set data structure represents a set of packages and is used for the current installed set, the sets available from upstream sources, and the set currently being install during a transaction. Tiered systems such as rpm+yum, deb+apt etc end up duplicating and reimplementing common operations on packages. Other systems typically pull in external database libraries to manage the package meta data and in some cases each layer in the stack uses a different database dependency to represent essentially the same data. - Using external database libraries may seem a good idea up front, but monotone vs git is a good example of how you need to control the data structure and the on-disk format to really get excellent performance. The razor package set data structure is fairly simple; it's an read-only, mmap()'able on-disk data structure. The package set has a sorted index of the packages in the set, a sorted index of all dependencies and a sorted, compact directory of all files in all the packages. Operations such as merging package sets, satisfying requires from one set against another can all be implemented in linear time. Razor implements the package set representation down to the bytes on the disk and can optimize the representation and access methods to make the necessary operations fast and reliable. - The set of installed packages on a system is represented by just one package set file. As we install a set of new packages, we prepare the new package set a temporary file and once the install has succeeded, we copy the package set file to the real filename. If there is a system crash, razor will notice the temporary file on boot and resume the update. - We want to keep the number of dependencies down in a system critical component such as the package manager. Between rpm and yum we're pulling in berkeley db, sqlite, expat, python. - During update of several packages rpm+yum leaves the system in an inconsistent state for long periods of time. Power failure in this window causes critical system corruption. We want to minimize the window.