You can try the 'rbk' (Reproducible Build with KVM) script from https://github.com/bmwiedemann/reproducibleopensuse I am using disorderfs in osc builds (in a hacky way) like this: https://github.com/bmwiedemann/reproducible-faketools/blob/master/extra/disorderfs.sh sometimes it also reduces races like in https://build.opensuse.org/request/show/510387 When we produce .pyc files, would that be once python call taking a directory and producing many .pyc files in one go? Then maybe the order of processing them makes a difference and we could avoid that by always processing them in the same order. Is there asynchronous garbage collection that could matter for the reference counts?