- colin-passwd.bin:
    - see <https://search.nixos.org/options?channel=unstable&show=users.users.%3Cname%3E.hashedPasswordFile&from=0&size=50&sort=relevance&type=packages&query=users.users>
    - update by running `sudo passwd colin` and then taking the 2nd item from the colin: line in /etc/shadow
    - N.B.: you MUST do `sudo passwd colin` instead of just `passwd`, i guess because of immutable users or something
- guest/authorized_keys.bin
    - who's allowed to login to the guest account