When installing the Squid RPM, you get two instances of the error: user squid does not exist - using root Shouldn't the install scripts for squid create these users? It seems that running it as root would be a security hole...
It adds the user as part of the %pre script ; it's possible the useradd failed, I suppose, due to lack of permissions or somesuch.
It's failing because there's a random squid group in NIS. Bleah.