Just to be clear, when a reconfigure fails you can make any necessary changes and run it again. Guix operations are atomic so it doesn't actually change the state of your system in any way until it finishes.
But, if you're asking about rolling back the "guix pull" so that you can run reconfigure with the older versions as if you had never ran "guix pull" in the first place, then I think you could try this: guix describe which should print out the "commit" used when you last reconfigured the system. Then you could try the following command with <commit-string> replaced with the value you got above: guix pull --commit=<commit-string> That should make sure your package data matches what was used last time you successfully reconfigured. As for the swapfile, it should work exactly how you showed. That error makes me think the problem is with how you set up the swapfile. Did you run "dd" to allocate space for the swapfile?