The 03.07.10 at 09:55, Peer Stefan wrote:
This is a new one to me, but I encountered many other problems. E.g. DNS-caching after the TTL expired, etc.
Contrary to its name, nscd does not caches explicitly DNS. Acording to its man page: Nscd provides cacheing for the passwd(5), group(5) and hosts(5) databases through standard libc interfaces, such as getpwnam(3), getpwuid(3), getgrnam(3), getgrgid(3), gethostbyname(3) and others. Each cache has a separate TTL (time-to-live) for its data; modifying the local database ( /etc/passwd, and so forth) causes that the cache becomes invalidated within fifteen seconds. Note that the shadow file is specifically not cached. getspnam(3) calls remain uncached as a result. And: Nscd doesn't know anything about the underlaying protocols for a service. This also means, that if you change /etc/resolv.conf for DNS queries, nscd will continue to use the old one if you have configured /etc/nss witch.conf(5) to use DNS for host lookups. In such a case, you need to restart nscd. And, the suse configuration dissables caching of DNS. The /etc/nscd.conf has: # !!!!!WARNING!!!!! Host cache is insecure!!! The mechanism in nscd to # cache hosts will cause your local system to not be able to trust # forward/reverse lookup checks. DO NOT USE THIS if your system relies on # this sort of security mechanism. Use a caching DNS server instead. enable-cache hosts no Previously, I used to disable it to conserve memory. Now I have it always enabled, and I don't notice it existence. Now that I think... it is watching for certain files being modified: it might be responsible for peridic disk activity. I would try to disable it in laptops. -- Cheers, Carlos Robinson