[Triumf-linux-managers] SL5 authconfig nis/dns misconfiguration

[Konstantin Olchanski]

On our SL5 machines I was seeing problems with DNS - programs
being stuck inside gethostbyname(), with stack trace indicating they
were doing something inside the NIS code. Very odd.

It turns out that "authconfig --enablenis ..." changes /etc/nsswitch.conf
line "hosts: ..." to read "hosts: files nis dns".

(notice the "nis" entry)

This makes the DNS service to first query NIS, then query
the TRIUMF DNS when resolving hostnames.

This is definitely a mistake because none of the NIS clusters
we use are configured to resolve hostnames via NIS. DNS should
always be used for this.

In fact I see that this problem did not exist in SL4 - I only
see misconfigured SL5 machines, but no misconfigured SL4 ones.

To correct this problem you can edit /etc/nsswitch.conf to
read "hosts: files dns" or run this sed script:

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

Filed Red Hat bug: https://bugzilla.redhat.com/show_bug.cgi?id=472565

-- 
Konstantin Olchanski
Data Acquisition Systems: The Bytes Must Flow!
Email: olchansk-at-triumf-dot-ca
Snail mail: 4004 Wesbrook Mall, TRIUMF, Vancouver, B.C., V6T 2A3, Canada