ubuntu-sethostname.sh

#!/bin/sh
# Filename:     /etc/dhcp/dhclient-exit-hooks.d/sethostname
# Purpose:      Used by dhclient-script to set the hostname of the system
#               to match the DNS information for the host as provided by
#               DHCP.
# logs in /var/log/syslog
#

echo dhclient-exit-hooks.d/sethostname: reason = $reason, interface = $interface

if [ "$reason" != BOUND ] && [ "$reason" != RENEW ] \
   && [ "$reason" != REBIND ] && [ "$reason" != REBOOT ]
then
        return
fi

if [ $interface != "eth0" ]; then
    return
fi

# for debugging:
echo dhclient-exit-hooks.d/sethostname: BEGIN
 
echo new_ip_address=$new_ip_address
echo new_host_name=$new_host_name
echo new_domain_name=$new_domain_name
 
oldhostname=$(hostname -s)
if [ $oldhostname != $new_host_name ]; then
 
    # Rename Host
    echo $new_host_name > /etc/hostname
    hostname -F /etc/hostname
 
    # Rename Host
    echo $new_host_name > /etc/hostname
    hostname -F /etc/hostname

    # Rename Domain
    domainname $new_domain_name

    # Update /etc/hosts if needed
    TMPHOSTS=/etc/hosts.dhcp.new
    if ! grep "$new_ip_address $new_host_name.$new_domain_name $new_host_name" /etc/hosts; then
        # Remove the 127.0.1.1 put there by the debian installer
        grep -v '127\.0\.1\.1 ' < /etc/hosts > $TMPHOSTS
        # Add the our new ip address and name
        echo "$new_ip_address $new_host_name.$new_domain_name $new_host_name" >> $TMPHOSTS
        mv $TMPHOSTS /etc/hosts
    fi
fi
echo dhclient-exit-hooks.d/sethostname: END