On 2022-01-22 at 21:23, gene heskett wrote: > On Saturday, January 22, 2022 9:08:02 PM EST David Wright wrote: > >> On Sat 22 Jan 2022 at 19:07:35 (-0500), The Wanderer wrote: >> > This is the line which contains the directives involved. >> > >> > The 'files' directive tells your system to check local files first; >> > the list of files involved is in the FILES section near the end of >> > 'man nsswitch.conf', and /etc/hosts is in that list. >> > >> > The 'mdns4_minimal' directive tells your system to check "multicast >> > DNS" first; I'm not familiar with the details of this, but Google >> > should be helpful. The [NOTFOUND=return] tag says - I think - that >> > if this check returns a report that the lookup was successful but >> > that no match was found, the system should return that result and >> > stop checking. >> > >> > The 'dns' directive tells your system to check the DNS system proper. >> > Given that this is after the [NOTFOUND=return] tag, as far as I can >> > see this should never be reached, but I presume it's there for a >> > reason; my best guess is that mDNS will usually not be available, so >> > the check will return UNAVAIL, which (per the man page) will by >> > default tell the system to continue to the next check (which is this >> > one). >> >> Rather than its not being available, it shouldn't even try with mDNS >> unless the name ends in .local, so it will skip to dns. Hmm. Looking at nsswitch.conf(5), it seems clear that the mdns4_minimal module must return *something* in that case, so I wonder what it might be. The obvious thing to return is NOTFOUND, but this tag turns the result of that from "continue to try the next thing" to "stop processing, and report back that no match was found", so that isn't plausible. >> This is what catches people out when they think that .local is a good >> choice for some random LAN, rather than one from the recommended list: >> .corp, .home or .mail. >> > You're changing the subject again. It doesn't look that way to me; he's explaining something I misunderstood, which provides more context. This might be branching out a bit from what your original discussion was about, but that's neither unexpected (thread drift is a thing, as are subthreads) nor - so long as your original subject is still being addressed, which it seems to be - a real problem. > AFAIK, the only .local is in the users directory, as a subdir. Exactly > NONE of my hostnames contain a .local postfix. That's exactly as expected. For the hostnames which are in /etc/hosts, the lookup process won't ever get this far, so the question of a '.local' suffix won't even become relevant. For the hostnames which aren't in that file, since none of them have that suffix, the mdns4_minimal entry in nsswitch.conf won't ever trigger, so any names that get that far will just proceed on for lookup via standard DNS. -- The Wanderer The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man. -- George Bernard Shaw
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