Red Hat Bugzilla – Bug 58568
glibc does not exactly follow nsswitch.conf settings
Last modified: 2016-11-24 10:21:16 EST
Description of Problem:
DNS requests made ahead of NIS requests despite the settings in nsswitch.conf.
Version-Release number of selected component (if applicable):glibc-2.2.4-13
Steps to Reproduce:
1. configure 7.2 as NIS client, check default nsswitch.conf settings: hosts: ..
nis dns. NIS comes first.
2. make sure that NIS hosts map contains some names. For example include following:
3. start "tcpdump port 53" on one terminal and "ping glibcnisbug" on another
tcpdump shows DNS requests made to the default DNS server asking for an IP
address of glibcnisbug.defaultdomain.com, where defaultdomain is "search" from
No DNS requests made, because NIS request must be made first.
This bug was found when DNS server went offline thus causing a huge delay in
name resolution. Investigation revealed that DNS requests were made before NIS
despite settings in nsswitch.conf
I have similar problem when the name servers
for lucon.org were off-line. Even though I put
x.x.x.x ocean.lucon.org lucon.org
in /etc/hosts and there is
hosts: files nisplus nis dns
# ssh lucon.org
took a long time to resolve since it
tried DNS first. I tracked it down
to the way how getaddrinfo works. But I never
found time to fix it since my name server
is working now.
Bug 71546: ldap for user files always used, regardless of nsswitch.conf
Bug 66682: nis for user files always used, regardless of nsswitch.conf
Bug 63631: local users never authenticated if ldap server down
It appears that this nsswitch.conf order problem has been resolved in rawhide.
A clarification on:
You should NOT install those RPMs on a production system. Rawhide
is raw bits. Those RPMs were only in relationship to various DNS
issues. Those rpms have a number of non-DNS related problems.
For example, they cause the rpm command to dump core. They did,
however, resolve the DNS issues, with the possible exception of
excessive IPv6 lookups.
Now there are RPMs which you can use on production systems. RHL9 should handle
this well. I've fixed a few more problem especially related to nscd and ldsp
which will be in the next binary. Closing the bug now.