Bug 1371683

Summary:	nss-mdns should not unconditionally add itself to /etc/nsswitch.conf during RPM updates
Product:	[Fedora] Fedora	Reporter:	Chris Siebenmann <cks-rhbugzilla>
Component:	nss-mdns	Assignee:	Lennart Poettering <lpoetter>
Status:	CLOSED EOL	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	24	CC:	akos.ladanyi, lpoetter, meta
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Last Closed:	2017-08-08 16:56:32 UTC	Type:	Bug
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Description Chris Siebenmann 2016-08-30 19:22:47 UTC

Description of problem:

If you have explicitly removed 'mdns4_minimal [NOTFOUND=return]' from your
'hosts:' line in /etc/nsswitch.conf, installing any nss-mdns update will
unconditionally add it back. This is completely wrong behavior unless
Fedora considers nss-mdns a required hosts resolution step, and I don't
think it should. In my situation I actively do not want to resolve .local
names from the local network; it is an anti-feature to foist this on me.

Version-Release number of selected component (if applicable):

nss-mdns-0.10-17.fc24.x86_64
nss-mdns-0.10-17.fc24.i686

How reproducible:

Completely.

Steps to Reproduce:
1. Install a Fedora 24 system.
2. Edit /etc/nsswitch.conf to remove 'mdns4_minimal [NOTFOUND=return]'
   from the 'hosts:' line.
3. Do 'dnf reinstall nss-mdns'
4. Observe that mdns4_minimal is back in your /etc/nsswitch.conf

The 'dnf reinstall' is kind of a hack here for simple problem
reproduction, because the real problem comes when either there's
a nss-mdns update within a Fedora release or you upgrade from one
Fedora release to another. However, Fedora 24 doesn't currently
have a nss-mdns update so I can't give you a simpler, exact
reproduction.

Additional info:

This is a problem in nss-mdns's postinstall script, in that it
performs its nsswitch.conf editing without checking to see if
it is being upgraded (or downgraded) instead of installed. The
preuninstall script gets this correct, only force-removing
mdns4_minimal from nsswitch.conf if the RPM is being completely
uninstalled.

(You can see that this is the case by inspection; the if
condition in the script is just '[ -f /etc/nsswitch.conf ]'.
The preuninstall script checks '"$1" -eq 0' as well.)

Comment 1 mathew 2017-01-09 20:13:19 UTC

I had the opposite problem. Upgrading to Fedora 25 overwrote my nsswitch.conf and removed the zeroconf support that I explicitly wanted.

I'm not sure which package did it. 'dnf reinstall nss-mdns' doesn't seem to do it.

So I would add that nss-mdns should not be explicitly removed from /etc/nsswitch.conf during RPM updates either.

Comment 2 mathew 2017-02-21 15:13:54 UTC

And nsswitch.conf just got overwritten again during a routine update. Maybe glibc is doing it?

Comment 3 Fedora End Of Life 2017-07-25 22:45:32 UTC

This message is a reminder that Fedora 24 is nearing its end of life.
Approximately 2 (two) weeks from now Fedora will stop maintaining
and issuing updates for Fedora 24. It is Fedora's policy to close all
bug reports from releases that are no longer maintained. At that time
this bug will be closed as EOL if it remains open with a Fedora  'version'
of '24'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version'
to a later Fedora version.

Thank you for reporting this issue and we are sorry that we were not
able to fix it before Fedora 24 is end of life. If you would still like
to see this bug fixed and are able to reproduce it against a later version
of Fedora, you are encouraged  change the 'version' to a later Fedora
version prior this bug is closed as described in the policy above.

Although we aim to fix as many bugs as possible during every release's
lifetime, sometimes those efforts are overtaken by events. Often a
more recent Fedora release includes newer upstream software that fixes
bugs or makes them obsolete.

Comment 4 Fedora End Of Life 2017-08-08 16:56:32 UTC

Fedora 24 changed to end-of-life (EOL) status on 2017-08-08. Fedora 24 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of
Fedora please feel free to reopen this bug against that version. If you
are unable to reopen this bug, please file a new report against the
current release. If you experience problems, please add a comment to this
bug.

Thank you for reporting this bug and we are sorry it could not be fixed.