Wednesday, May 28, 2014

GSoC 2014 - week 2

It's been a week (and one day) since my last post, so I'd like to share my progress. I've been continuing with refactoring the mock initialization and splitting the functionality into smaller pieces.

DNF support
I've implemented suport for using DNF as a package manager instead of Yum. Both package managers are used through a common abstract class and which one is used is decided based on the configuration ('package_manager' option, which defaults to yum when unspecified). This behavior can be overriden by explicitly passing --yum or --dnf commandline options. There have been some concerns whether the installroot support in DNF is working correctly, but I've been able to do a rebuild of a package using DNF exclusively and it worked fine without any changes to the config.

Direct interaction with package manager
One of the features I mentioned in my proposal was providing direct interaction with the package manager. Current mock allows invoking only small subset of commands that Yum/DNF provide. I added a '--pm-cmd' command that allows invoking arbitrary package management commands. There are also '--yum-cmd' and '--dnf-cmd' that are just shortcuts to specifying '--yum' or '--dnf' and the '--pm-cmd' option.
mock --yum-cmd reinstall expat-devel

Mock interactivity
The week before I implemented shared locking that allows multiple mock processes to operate on the same buildroot and I was able to get more instances of mock shell. But that was only part of what needed to be done, because other mock commands had their own cleanup logic, thus usually killing still running processes and clashing while unmounting shared devices. I've been working on integrating the new initialization/cleanup scheme into all remaining commands and now there shouldn't be such clashes anymore. I've also made the cleanup more reliable (runs even if exception is raised) and the initialization more resistant - dealing with possible remaining mounts from previous run without needing the user to unmount them manually. I'm also trying to make the startup faster by marking what parts of initialization which were already done, therefore don't need to be repeated.

Next steps
I'd like to start making foundation for the main feature I want to implement - support for using LVM for storing buildroot images and therefore being able to leverage it's snapshoting features.

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