Ubuntu Enterprise Cloud
I had problems with ssh passwordless logins taking ages on the hadoop Ubuntu cluster I was working on. This was fixed by adding a 'UseDNS no' entry to /etc/ssh/sshd_config file and restarting the ssh daemon using the command sudo /etc/init.d/ssh restart.
The compute nodes on the cluster could not access the internet so NAT had to be setup on the head hadoop node.
Where eth0 is the network card with access to the private network.
The following NAT was setup as follows using the command 'sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE' and '/proc/sys/net/ipv4/ip_forward' file entry should be 1.
Restart dnsmasq using the following command 'sudo /etc/init.d/dnsmasq restart'.
Configure the NAT with the following command 'iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE'. Where eth1 is the network card with access to the internet.
I tested the cluster by pinging a url on the internet with the command 'ping -c 4 google.com' the result was as follows
PING google.com (188.8.131.52) 56(84) bytes of data.
64 bytes from wy-in-f104.1e100.net (184.108.40.206): icmp_seq=1 ttl=51 time=18.8 ms
64 bytes from wy-in-f104.1e100.net (220.127.116.11): icmp_seq=2 ttl=51 time=18.8 ms
64 bytes from wy-in-f104.1e100.net (18.104.22.168): icmp_seq=3 ttl=51 time=18.9 ms
64 bytes from wy-in-f104.1e100.net (22.214.171.124): icmp_seq=4 ttl=51 time=18.8 ms
--- google.com ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3004ms
rtt min/avg/max/mdev = 18.800/18.840/18.912/0.106 ms
thus proving that the NAT settings had worked.
Information used was from the page http://www.ubuntugeek.com/sharing-internet-connection-in-ubuntu.html for this blog