Comment 2 for bug 1624071

Martin Pitt (pitti) wrote :

Thanks for reporting this, well spotted!

The reason for having "dns" is *not* to guard against failures of resolved -- if the daemon is not running, then nss-resolve already falls back to glibc's resolver (i. e. "dns").

The reason is that libnss-resolve itself might not be available. E. g. you might have the amd64 version installed that inserts itself into nsswitch. But then you start a 32 bit package from an i386 deb which needs libnss-resolve:i386 and that might not be installed. That needs "dns" otherwise you get a "System error" when resolving.

I actually thought that "resolve [NOTFOUND=return] dns" should do the right thing, as that's the crucial case -- its default action is "continue", and if a DNS entry fails validation we don't want to fall back to "dns". The actions for success/unavail/tryagain already seem right. But this doesn't work, "ping" still succeeds and falls back to dns.

So I'm not sure how to solve this. Ideally we would have a syntax which would ignore the absence of the "resolve" NSS module but accept if that says "not found". Or we need to ensure that for any :arch package the corresponding libnss-resolve:arch is installed.