I am having this issue right now. Exact same.
sudo: unable to resolve host HOSTNAMEHERE: Name or service not known
Host file is stripped down to this after TinyCP install:
127.0.0.1 localhost.localdomain localhost
::1 ip6-localhost ip6-loopback
I added the hostname entry back in just below the local host entry, and after reboot, gone again. This makes TinyCP unusable.