Host name not getting resolved

[jayachandran.g]

Hi all

I have two servers in cluster. SRV1 and SRV2.One of the processes in SRV2 server is trying to get the hostname for the SRV1 servers ipaddress.

The Error: Unable to get the hostname for the ipaddress 10.1.1.1 (10.1.1.1 is the SRV1 ipaddress)

I have checked the /etc/hosts file, found that the ipaddress and the host name for this ipaddress is missing in both the servers.

Then I have added the ipaddress and host name in both of the servers.

But then too problem is not solved.

help me, thanks in advance

[RAC_1 · Accepted solution]

Do both servers use /etc/hosts for host name resolution? Check /etc/nsswitch.conf file.

[Victor BERRIDGE]

Hi,
Have you checked your /etc/nsswitch.conf file and /etc/resolv.conf, their perms and for nsswitch.conf if you do have something like:
hosts: files [NOTFOUND=continue] dns

Are these addresses correctly routed?
(correct subnet route, netmask..)

What are the perms on your hosts file? (444)

All the best
Victor

[jayachandran.g]

Hi RAC/Victor

There is no nsswitch.conf (or) resolv.conf file in the servers.

I have already checked and rectified the host file.

entry for the ipaddress 10.1.1.1 was missing previously.And I have already added the missing Ipaddress to the host files.

[Darrel Louis]

Hi,

Have you added the servers to the /etc/hosts file asfollow:

10.1.1.1 srv1.domain.com srv1

And as already mentioned check your /etc/nsswitch.conf file.
If the file doesn't exists copy it.
# cp /etc/nsswitch.files /etc/nsswitch.conf
Modify the line hosts:
hosts: files [ NOTFOUND=continue ] dns

Goodluck

Darrel Louis

[MarkSyder]

You will probably have a file /etc/nsswitch.compat, which can be copied to nsswitch.conf.

You should set it up so it uses files first for hosts.

Mark Syder (like the drink but spelt different)

[Victor BERRIDGE]

Hi again!
What servers and most important what cluster are you talking about?
It may be nothing to do with the servers themselves but more the way a process is looking for his "hostname"...
A cluster like mcSG will have on a host ist address (HW-server) + the addresses of the packages running on it....

All the best
Victor

[Frank de Vries]

Otherwise you can create the nsswitch.conf
in the /etc directory and put this
contents in it

hosts: files [NOTFOUND=continue UNAVAIL=continue] dns [NOTFOUND=return UNAVAIL=continue TRYAGAIN=return]

If will first check your local /etc/hosts
and then check your dns

You can troubleshoot with nslookup command:

I have a host called frank only in /etc/hosts
10.214.9.118 frank

When I use nslookup it will show where it
resolved it.

[orapic@orasrv1:]/etc<>>> nslookup
Using /etc/hosts on: orasrv1

> frank
Using /etc/hosts on: orasrv1

looking up FILES
Name: frank
Address: 10.214.9.118

>

Good luck

[jayachandran.g]

Hi All

Host name to IP address maping is working fine.

Ip to Hostname is not working.

Regards
Jayachandran.G

[spex]

Hi,

Try using nslookup to do reverse DNS:

# nslookup
# nslookup

If the IP address is resolved correctly, try restarting the processes. This will force them to re-read configuration.

Did you create /etc/nsswitch.conf and /etc/resolv.conf ?

PCS

[Jaime Bolanos Rojas.]

Jayachandran,

Even thought it looks like we repeating ourselves, you should have 3 very important files in the system.

/etc/hosts
/etc/nsswitch.conf
/etc/resolv.conf

please make sure that they are on the system and configure properly. You can always type man and the name of the file for more info.

Regards,

jaime.

[Chan 007]

Hi,

1. Try ping from Both servers with Hostname, not down the IP address.

2. Try to ping with those IP address, is this ping working?

3. Try to do a "tracert" from your desktop and check the hosts are reachable.

4. Check for hardcoding IP address in your script.

5. Run netstat -nr and check your gateway and mask are fin on both servers.

Chan

[jayachandran.g]

Hi all

It is working now. Thanks for all of your valuble replies.

Steps that are followed to solve

1) Copied the file nsswitch.files as
nsswitch.conf

#cp nsswitch.files nsswitch.conf

(Tried nsslookup but fialed)

2) Except the line "hosts: file" all other
lines are hashed in the nsswitch.conf.

(Tried nsslookup but failed)

3) As if these servers are there in cluster,
hosts file where having more
then one ipaddress for the same server.

example
cat /etc/hosts

10.1.1.2 SRV1
10.1.1.1 SRV1

I have hased out other entries except for the ipaddress for which the error is reporting

cat /etc/hosts
#10.1.1.2 SRV1
10.1.1.1 SRV1

Now nssokup is working fine.

(Note: I have even removed my nsswitch.conf file then too nsslookup is working fine).

I supspect the entries in the hosts file.

Please correct me if i'm wrong.

[Victor BERRIDGE]

Hi again,

Well you didnt tell us you had 2 entries to the same server in /etc/hosts, otherwise we would have said:
Its the first that is used...

It would have saved time in your first post to have given the content of /etc/hosts...

All the best
Victor

[jayachandran.g]

Hi Victor

I accecpt that is a mistake..

I'm was trying nslookup for ipaddress and not for a hostname.So i felt multiple entires for the same hostname dosen't matter.

#nslookup
>10.1.1.1 (for this ipddress there is only one entry in my host file)

[jayachandran.g]

Thanks for all your help..