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I've tested that using a very short lived (TTL of 3 seconds) of a DNS A record. nscd only respects positive-time-to-live from /etc/nscd.conf and not DNS TTLS as it should. It has very nasty side effects if the record in question is (e.g.) the IP of the ldap server :) To reproduce the problem, have a short lived A domain (e.g. 3 seconds) change its IP. hosts $domain will answer the correct new IP after at most 3 seconds, whereas getent hosts $domain will always return the old IP (until the nscd.conf positive-time-to-live expires).
nscd does respect TTL. Only for getaddrinfo but this is OK since no program should have use gethostbyaddr*.
Given the number of pre-2001 software still around (time at which gethostby* calls were marked obsoletes) that indeed use gethostby* (and the number of more recent software using it too, even being obsolete) you are just knowingly breaking them. Quite interesting indeed. Btw I tested this _BUG_ doing: $ getent hosts ttl3.madism.org which after 3 seconds does not make a new request as it should (running nscd in debug mode shows it quite unambiguously). Interestingly enough, getent (from the libc you know) does that: $ ltrace getent hosts ttl3.madism.org > /dev/null __libc_start_main(0x402e40, 3, 0x7fffeead3c08, 0x403c40, 0x403c30 <unfinished ...> mtrace() = <void> setlocale(6, "") = "LC_CTYPE=fr_FR.utf8;LC_NUMERIC=f"... textdomain("libc") = "libc" argp_parse(0x5053e0, 3, 0x7fffeead3c08, 0, 0x7fffeead3af4) = 0 strcmp("hosts", "hosts") = 0 inet_pton(10, 0x7fffeead547b, 0x7fffeead3aa0, 0x5070c0, 0x5070d0) = 0 inet_pton(2, 0x7fffeead547b, 0x7fffeead3aa0, 0, 0x7fffeead3a40) = 0 gethostbyname2(0x7fffeead547b, 10, 0x7fffeead3aa0, 116, 0) = 0 gethostbyname2(0x7fffeead547b, 2, 1, 0, 0x2ae1c05b8790) = 0x2ae1bc33cfe0 inet_ntop(2, 0x5070f8, 0x7fffeead3a40, 46, 0) = 0x7fffeead3a40 printf("%-15s %s", "127.0.0.1", "ttl3.madism.org") = 31 +++ exited (status 0) +++ So now I'm not surprised anymore I guess. You are breaking your own software. IMHO, given how broken gethostby* are with the use of nscd, either hosts caching should be removed, or gethostby* generate a warning at link time so that people get to know that those are not supported at *all*.