Iptables Port Redirection

How to redirect to another port on the same server:

iptables -t nat -A PREROUTING -p tcp -i eth0 -d $SERVER –dport 25 -j DNAT –to $SERVER:2525

Redirect a port to another server ($SERVER2):

iptables -t nat -A PREROUTING -p tcp -i eth0 -d $SERVER1 –dport 25 -j DNAT –to $SERVER2:25
iptables -A FORWARD -p tcp -i eth0 -d $SERVER2 –dport 25 -j ACCEPT
iptables -t nat -A POSTROUTING -d $SERVER2 -p tcp –dport 25 -o eth0 -j MASQUERADE
iptables -A FORWARD -p tcp -i eth0 -s $SERVER2 –sport 25 -j ACCEPT
iptables -t nat -A POSTROUTING -p tcp -s $SERVER2 –sport 25 -j SNAT –to $SERVER1

Power requirements for Dell servers

Dell PowerEdge 1550
Total Power (Watts): 317
Total Power (VA): 453
Total Thermal (BTU/hr): 1083

Dell PowerEdge 1650
Total Power (Watts): 206
Total Power (VA): 294
Total Thermal (BTU/hr): 704

Dell PowerEdge 1850
Total Power (Watts): 287
Total Power (VA): 410
Total Thermal (BTU/hr): 980

Dell PowerEdge 1950
Total Power (Watts): 317
Total Power (VA): 453
Total Thermal (BTU/hr): 1083

Dell PowerEdge 2650
Total Power (Watts): 267
Total Power (VA): 381
Total Thermal (BTU/hr): 912

Dell PowerEdge 2850
Total Power (Watts): 398
Total Power (VA): 568
Total Thermal (BTU/hr): 1359

Dell PowerEdge 2950
Total Power (Watts): 356
Total Power (VA): 508
Total Thermal (BTU/hr): 1216

List open files

This command lists regular files that are open by running processes:

lsof -n | grep REG

Or just grep for the file you are looking for:

lsof -n | grep $filename

You can also see what ports are open using lsof -i.