nslookup not resolving hostname

Question

I can't seem to get nslookup to resolve correctly.

Here is my hosts file:

[root@clc-host ge2011.11]# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

192.168.0.101   clc-host
192.168.0.101   clc-host.novalocal

Here is the results of nslookup:

[eamorr@clc-host ge2011.11]$ nslookup clc-host
Server:         10.77.254.1
Address:        10.77.254.1#53

** server can't find clc-host: NXDOMAIN

[eamorr@clc-host ge2011.11]$ nslookup clc-host.novalocal
Server:         10.77.254.1
Address:        10.77.254.1#53

** server can't find clc-host.novalocal: NXDOMAIN

Do you know how I might fix this issue? All I want to do is have "clc-host" resolve to 192.168.0.101. I need both "clc-host" and "clc-host.novalocal" to resolve to 192.168.0.101!!!

Here is " ifconfig -a"

[eamorr@clc-host ge2011.11]$ ifconfig -a
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1450
        inet 192.168.0.101  netmask 255.255.255.0  broadcast 192.168.0.255
        ether fa:16:3e:xx:xx:xx  txqueuelen 1000  (Ethernet)
        RX packets 506130  bytes 500159111 (476.9 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 318940  bytes 80431845 (76.7 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        loop  txqueuelen 0  (Local Loopback)
        RX packets 251781  bytes 57945811 (55.2 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 251781  bytes 57945811 (55.2 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
        ether 52:54:00:xx:xx:xx  txqueuelen 0  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0-nic: flags=4098<BROADCAST,MULTICAST>  mtu 1500
        ether 52:54:00:xx:xx:xx  txqueuelen 500  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

I think there is some internal problem with the DNS and I don't know how to fix it. I don't think it's related to /etc/hosts

Do I need to install a full DNS server locally?

I'm trying to install 3rd party software - the GUI won't accept an IP address and I have to use the machine's hostname, which isn't resolving...

Note your hosts file is invalid, you cannot have two entries for the same IP. You need to include a space-separated list of names after each IP - anything else will result in Odd Things (TM) happening. — Boris the Spider, Jun 27 '16 at 14:28

score 11 · Answer 1 · answered Jun 27 '16 at 11:06

11

nslookup (name server lookup) doesn't work with entries in the host file, instead it queries the DNS system, which doesn't know about names defined in your local hosts file. Try to just ping the name or access it in the web browser.

answered Jun 27 '16 at 11:06

Sven

98,649
14
180
226

Hello, I can ping the machine alright. I need to be able to resolve it! – EHQ Jun 27 '16 at 13:57
1

If you can ping it, you can resolve it. By it's very nature, everything in `/etc/hosts` only works on that exact machine. If you need the entry to work on more than one machine, you need to put into in every one or use DNS anyway. – Sven Jun 27 '16 at 14:00
Oh, and if the installer of the software doesn't work with `hosts` entries, there will be no way around setting up a DNS server. However, even that might fail if the installer insists on a public DNS entry. – Sven Jun 27 '16 at 14:02

HBruijn · Answer 2 · 2016-06-27T12:00:32.627

8

/etc/hosts is not DNS.

Please use the right tool to test; nslookup and dig always consult DNS and never use the entries in /etc/hosts (or for that matter NIS, LDAP or other alternative hosts databases).

The fact that the /etc/hosts file is used at all by your system and the priority it has is determined by the Name Service Switch libraries configured in /etc/resolv.conf

getent hosts <hostname | ip-address> will use the C resolver functions, honours nsswitch.conf and will show entries from your hosts file if those have priority and is what most closely mimics what your system will resolve.

edited Jun 27 '16 at 12:00

answered Jun 27 '16 at 11:53

HBruijn

77,029
24
135
201

I understand /etc/hosts is not DNS. I'm just trying to figure out how to do this simply and cleanly without having to run a DNS server! – EHQ Jun 27 '16 at 13:58
`getent hosts clc-host` returns as expected. But `nslookup` still can't find anything? – EHQ Jun 27 '16 at 13:59
3

@EHQ: As both HBruijn and I said, `nslookup` doesn't work with `host` file entries, period. However, `nslookup` not finding the name doesn't mean your can't use it on your local machine. – Sven Jun 27 '16 at 14:01
I believe that nowadays one should be using `getent ahosts` instead of `getent hosts` because `getent hosts` uses `gethostbyaddr()` or `gethostbyname*()` which are obsolete. If I have understood correctly, `getent hosts` emulates how old UNIX C programs used to work and `getent ahosts` emulates the way moderm programs should work. – Mikko Rantalainen Oct 02 '17 at 06:11

nslookup not resolving hostname

2 Answers2