I'm not sure if I'm reading your message as you intended, but for the record, 127.0.0.1 should ALWAYS resolve to "localhost" - without the domain name, and NOT to the canonical hostname. If it does not, then a lot of things break. J' On Sat, Jan 18, 2014 at 10:32:31PM +0100, Ludovic Court??s wrote: So /etc/hosts is not enough for reverse lookups to work. With nscd turned off, I tried this: guile -c '(pk (gethostbyaddr (inet-pton AF_INET "127.0.0.1")))' If nsswitch.conf is removed, then that resolves to ???localhost??? (instead of the actual host name.) If, in addition, resolv.conf is removed, then that fails as seen above. With nsswitch.conf alone, it resolves correctly (Mark was right.) And this works with only ???hosts: files??? in nsswitch.conf. It???s surprising that there???s this discrepancy between how NSS works for getaddrinfo and for gethostbyaddr. At any rate, we may be able to solve this at the libc level. Thanks, Ludo???. -- PGP Public key ID: 1024D/2DE827B3 fingerprint = 8797 A26D 0854 2EAB 0285 A290 8A67 719C 2DE8 27B3 See http://sks-keyservers.net or any PGP keyserver for public key.