Set hostname

To set the hostname in Red Hat / CentOS 5:

vi /etc/sysconfig/network   #change it here
vi /etc/hosts               #and here
echo server1.example.com > /etc/hostname   #and here
hostname server1.example.com   #and here for good measure
/sbin/service network restart    #restart the network

for Ubuntu you just need

echo server1.example.com > /etc/hostname   #here
vi /etc/hosts                              #and here

Regenerate ssh server key

• The standard way to do this is:

rm /etc/ssh/ssh_host_*
dpkg-reconfigure openssh-server