People overestimate the importance of the Internet, and computer systems in general, for storing knowledge. Most of humanity's knowledge, and all of the critical knowledge, is stored in books. Many of those are printed on acid-free paper, which is well-known to survive centuries with essentially zero maintenance.

As long as people don't forget how to read, it's mostly a matter of repopulating the Earth and using libraries as a knowledge base. Even if the knowledge stored in the brains of all surviving humans was somehow wiped out, this should get us back to roughly the start of the 20th century in a relatively short time, and from that point on we can simply expect history to repeat itself (hopefully, without the "catastrophe" though).