TCP/IP name resolution

UNIX for Advanced & Expert Users
1

We have 2 Unix boxes.

AIX 4.3 RS/6000
Linux RedHat 6.1 Intel

There is a name server running on the linux machine. This is not used on the AIX machine ( it simply uses /etc/hosts ).

Now i have rsh permission denied problems and i suspect our AIX and tcp/ip name resolution.
I was told to login from the client to the server and run "last | head" to see what hostname the server is seeing.

First case: from LINUX to AIX ( rsh from linux to AIX works fine )
/bunolleken/users/joeri> last | head
joeri pts/20 linuxnol May 07 10:48 still logged in.

Hostname is "linuxnol". I have put this in /etc/hosts.equiv. everything OK

Second case: from AIX to LINUX ( rsh gives permission denied )
( last -a | head )
joeri pts/2 Tue May 7 10:51 still logged in ibm250.nollekens.be.220.4.125.in-addr.arpa

Hostname is "ibm250.nollekens.be.220.4.125.in-addr.arpa".
Weird name. It should simply be "ibm250"

Like i said. There i NO nameserver active on the AIX. simply hosts file.
This is comming from our AIX, right? But from where?

Joeri

2

No, it is comming from the nameserver on linux. The linux box knows the ip address that connected to it. It then uses dns to get the hostname. If you use nslookup (or dig or whatever linix uses) to lookup the ip address of the aix system on the linux system you will get the same result.

This is probably because the reverse entry needs a trailing dot.

3

a- Add the IP, host_name and aliases in the /etc/hosts in both machines.

In the AIX machine

if [ ! f /etc/netsvc.conf ]
then
echo "hosts=local,bind" > /etc/netsvc.conf
else
echo "review the hosts definitions in the /etc/netsvc.conf"
echo "hosts=local,bind"
fi

In the linux machine:

in the /etc/nsswitch.conf
hosts: files dns

b- Add the .rhosts in the home directory of the user in both machines:
example for root:

linux box:
echo "server_aix root" >> $HOME/.rhosts

aix box:
echo "server_linux root" >> $HOME/.rhosts

c- Permit the root login in both machines

linux box:

Add the apropiate entry in the /etc/securetty

aix box:

chuser login=true rlogin=true root

Good luck. Hugo.