/etc/resolv.conf permissions are 600 and name lookups fail for other users?

RaelOM · 10-16-2009, 07:41 AM

So, I'm having a problem and I've never seen it before.

/etc/resolv.conf was mode 600. Users besides 'root' were unable to resolv anything. As another user besides root, a nslookup would result in nameserver timeout and a ping would result in unknown host.

When I change the permissions to 644, it works fine for everyone.

So I understand it makes sense that everyone should have read capability to the resolv.conf file so ping can query who it should get resolution from, but according to our latest backup, this file has been mode 600 for quite some time, so our services should have been failing yesterday and not just appearing this morning?

Does anyone know anything about this?

Yesterday my peer added this server to our Active Directory domain using Likewise, would that have caused this error to appear?

madmadmod · 10-16-2009, 07:44 AM

did your services use cached information?

rizhun · 10-16-2009, 07:47 AM

Weird!

644 is definitely standard for /etc/reslov.conf though.

RaelOM · 10-16-2009, 09:53 AM

Yea, I thought of cache as well, and that's the only explanation I could come to, but if /etc/resolv.conf was 600 for awhile now, shouldn't this have been failing all along?

nsswitch.conf was modified but only for

< passwd: files
< group: files
---
> passwd: files lsass
> group: files lsass

Would that have any effect?

jlliagre · 10-16-2009, 11:08 AM

madmadmod got it right. /etc/resolv.conf need to be readable for all only if the name service cache daemon (nscd) isn't enabled, otherwise, 0600 is just fine.

What says (assuming you are running Solaris 10 or newer):

Code:

svcs -xv name-service-cache

?

RaelOM · 10-16-2009, 11:24 AM

Solaris 9, not using the new service implementation.

I don't see that nscd is running or has ever ran.

jlliagre · 10-16-2009, 11:33 AM

Nscd should and was certainly running before. It just died for some odd reason and that triggered the effect you are observing. Just restart it. It is quite useful anyway beyond that permission issue.

Code:

/usr/sbin/nscd

Note that this wouldn't have happened with Solaris 10 or newer.

RaelOM · 10-16-2009, 12:45 PM

BINGO

Never knew about nscd

Thanks!

I've audited my servers and foud three more with nscd not running but the perms on resolv.conf were correct, so we dodged the bullet and 9 more that had nscd running but bad perms on resolv.conf so we didn't get bit.

I've since fixed the perms and started nscd on all servers.

Thanks!