F32, mDNS, and nsswitch.conf

[Kevin Becker]

I've been using Fedora on my laptop for a few years now, and on a newly
built desktop for since just last summer.  I've never had an issue
upgrading, but I only recently became aware of the recommended post-
install steps.

https://docs.fedoraproject.org/en-US/quick-docs/dnf-system-upgrade/

So this time, after upgrading to Fedora 32 I followed the guide.  When
I was looking through the results of rpmconf -a, I chose to install the
newer config files as I hadn't made any local changes, except in
sshd_config. 

After the upgrade, it turned out I could no longer print from my
desktop.  My printer was discovered via mDNS and configured
automatically in the past, it was really nice actually.  I tried on my
laptop as well and had the same result.  I basically ignored it for a
few days, installing updates and seeing if it was fixed, but it never
was.  Monday I had a bunch of printing to do for my kid's "remote
learning" school assignments so I figured I'd dig into it. It turns out
mdns4_minimal had been removed from host resolution in nsswitch.conf. 
I restored the nsswitch.conf.bak on both machines and my printer is
back in business.

I'm not sure if this is a bug?  Was it removed for a reason or should I
report it?  Maybe it has been gone for a while now, and I've just been
bringing the config forward.  I suspect whatever package adds mDNS
functionality also adds the entry to the default config and then I
resotred the default back so this is basically user error.

[Tom Horsley]

On Tue, 05 May 2020 19:48:22 -0400
Kevin Becker wrote:

>  It turns out
>  mdns4_minimal had been removed from host resolution in nsswitch.conf. 
>  I restored the nsswitch.conf.bak on both machines and my printer is
>  back in business. 
Files like nsswitch.conf seem to be configured by the new
authselect stuff, though God knows which profile you need
to select to make it work. (Why mdns4_minimal helps, I have
no idea, it usually is what screws up my systems and I
have to take it out to make things work).

[Kevin Becker]

Well, my printer was autodiscovered and configured via mDNS, so with
the mnds4_minimal entry missing, it was not able to resolve the name. I
could've  gone an manually added it by IP address or a static DNS name
but I liked the simplicity of it working "automagically" and I never
remember the exact syntax I need and whether to set it up an IPP or
HTTP or LPR printer.  

I've had issues with the mdns4_minimal entry in the past when accessing
work resources over VPN, presumably because we have a .local Active
Directory domain at work and mDNS uses .local as well.  IIRC I had to
move the mdns entry further back in the list to make it work, but that
was a few years ago and probably on ubuntu.  I never had to mess with
it in Fedora until now.



On Tue, 2020-05-05 at 19:55 -0400, Tom Horsley wrote:
>  On Tue, 05 May 2020 19:48:22 -0400
>  Kevin Becker wrote:
>  
>  > It turns out
>  > mdns4_minimal had been removed from host resolution in
>  > nsswitch.conf. 
>  > I restored the nsswitch.conf.bak on both machines and my printer is
>  > back in business.
>  
>  Files like nsswitch.conf seem to be configured by the new
>  authselect stuff, though God knows which profile you need
>  to select to make it work. (Why mdns4_minimal helps, I have
>  no idea, it usually is what screws up my systems and I
>  have to take it out to make things work).
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Hi.

On Tue, 05 May 2020 19:48:22 -0400 Kevin Becker wrote:

>  It turns out mdns4_minimal had been removed from host resolution in
>  nsswitch.conf. 
This is a known bug:

 
https://fedoraproject.org/wiki/Common_F32_bugs#mDNS_.28multicast_DNS.29_b...

  This is resolved in the Fedora 32 final release.

Not quite sure thus ...

-- 
francis

[Kevin Becker]

I waited until the final release before upgrading.  But it's good to
know this is actually a bug and has already been found.
Thanks.

On Wed, 2020-05-06 at 13:03 +0200, Francis.Montagnac(a)inria.fr wrote:
>  Hi.
>  On Tue, 05 May 2020 19:48:22 -0400 Kevin Becker wrote:
>  > It turns out mdns4_minimal had been removed from host resolution
>  > innsswitch.conf.
>  
>  This is a known bug:
>    
>
> https://fedoraproject.org/wiki/Common_F32_bugs#mDNS_.28multicast_DNS.29_b...
>  
>    This is resolved in the Fedora 32 final release.
>  Not quite sure thus ...
>  -- francis_______________________________________________users
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