How to change the linux hostname?

# hostname
test.com

# hostname server.com

# hostname
server.com

# vi /etc/hostname
server.com

Now restart and see the changes.

Netstat in Linux

List all ports
# netstat -a | more

List all tcp ports using netstat -at
# netstat -at

List all udp ports using netstat -au
# netstat -au

List only listening ports
# netstat -l

List only listening TCP Ports using netstat -lt
# netstat -lt

List only listening UDP Ports using netstat -lu
# netstat -lu

List only the listening UNIX Ports using netstat -lx
# netstat -lx

Show statistics for all ports
# netstat -s

Show statistics for TCP/UDP ports
# netstat -st
# netstat -su

Display PID and program names
# netstat -pt

Don’t resolve host, port and user name
# netstat -an

Print netstat information continuously
# netstat -c

Find the non supportive Address families in your system
# netstat --verbose

Display the kernel routing information
# netstat -r

Find out on which port a program is running
# netstat -ap | grep ssh

Find out which process is using a particular port
# netstat -an | grep ':80'

Show the list of network interfaces
# netstat -i

Display extended information on the interfaces
# netstat -ie