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Bug 472565

Summary: authconfig --enablenis breaks DNS
Product: Red Hat Enterprise Linux 5 Reporter: Konstantin Olchanski <olchansk>
Component: authconfigAssignee: Tomas Mraz <tmraz>
Status: CLOSED NEXTRELEASE QA Contact: BaseOS QE <qe-baseos-auto>
Severity: medium Docs Contact:
Priority: medium    
Version: 5.2   
Target Milestone: rc   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
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Clone Of: Environment:
Last Closed: 2008-11-24 20:09:12 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description Konstantin Olchanski 2008-11-21 19:16:57 UTC 
authconfig-5.3.21-3.el5.x86_64 option "--enablenis" changes /etc/nsswitch.conf to read "hosts: files nis dns". Notice how by adding the "nis" entry, this configures DNS to query NIS before querying any name servers.

This behaviour is surprising. As a long time NIS user and administrator I have never ever used NIS to resolve DNS queries.

This actually happens to misbehave. I see programs stuck inside gethostbyname(), with gethostbyname() in turn being stuck trying to make NIS calls. (This is a no-bug - do not use NIS to do DNS!)

RHEL4 does not seem to have this problem. I see most of my SL4 machines read "hosts: files dns", so at least some older versions of authconfig did not have this problem.

Anyhow, I see no mention of any of this in authconfig documentation, authconfig rpm changelog or in Red Hat bugzilla.

To undo this unwanted change, run this sed script:

sed 's/^hosts:.*/hosts: files dns/' -i /etc/nsswitch.conf

K.O.
Comment 1 Tomas Mraz 2008-11-24 20:09:12 UTC 
As far as I know this was always the case - even in the RHEL-4 authconfig that if you enable nis for user information it will add it to hosts: in nsswitch.conf. 

So this is no regression.

But in the 5.3 update of Red Hat Enterprise Linux, there will be a new enhancement of authconfig that it will support --enablepreferdns option which will make it to put dns just after files before any other services such as nis.