changeip.py

#!/usr/bin/env python

import sys
from subprocess import call

gw = '.1'
mask = '255.255.255.0'
net = '.0'
broadcast = '.255'
dns = '8.8.8.8'

network_file = '/etc/network/interfaces'
reboot_text = ''
netdata = {}

def verify(ip_components):
    if ip_components[0] == '0':
        return False
    for octet in ip_components:
        if int(octet) > 255:
            return False
    return True

def reboot_server():
    print (netdata['reboot_text'])
    answer = raw_input('\nWould you like to restart the interface now? (Y/n): ') or "Y"
    if answer.lower() == "y":
        call("sudo ifdown eth0 && sudo ifup eth0", shell=True)

    return

def build_netdata(ipaddress):
    ip_components = ipaddress.split('.')
    baseip = '.'.join(ip_components[0:3])

    if not verify(ip_components):
        print ("This is not a valid IP address:  " + ipaddress)
        exit()

    netdata['ipaddr'] = ipaddress
    netdata['gw'] = baseip + gw
    netdata['mask'] = mask
    netdata['network'] = baseip + net
    netdata['broadcast'] = baseip + broadcast
    netdata['reboot_text'] = "I have created a /24 based IP Address and netmask based on {0}".format(netdata['ipaddr'])

    return netdata

def build_netfile(netdata):
    target_data = ''
    print ("Assuming {} mask, {} default gateway, {} dns.".format (mask, gw, dns))

    target_data += '##  This file written by changeip.py'
    target_data += '\nauto lo'
    target_data += '\niface lo inet loopback\n'
    target_data += '\nauto eth0'
    target_data += '\niface eth0 inet static'
    target_data += '\n  address ' + netdata['ipaddr']
    target_data += '\n  gateway ' + netdata['gw']
    target_data += '\n  netmask ' + netdata['mask']
    target_data += '\n  network ' + netdata['network']
    target_data += '\n  broadcast ' + netdata['broadcast']
    target_data += '\n  dns-nameservers ' + dns
    target_data += '\n'

    return target_data

def build_dhcpfile():
    target_data = '''
    # interfaces(5) file used by ifup(8) and ifdown(8)
    # Include files from /etc/network/interfaces.d:
    source-directory /etc/network/interfaces.d

    # The loopback network interface
    auto lo
    iface lo inet loopback

    auto eth0
    iface eth0 inet dhcp
    '''

    netdata['reboot_text'] = "I have setup the networking to look for a dhcp address."
    return target_data

def write_data(target_data):
    target_file = open(network_file, 'w')
    target_file.truncate()
    target_file.write(target_data)
    target_file.close()

    return

def main(argv):
    if len(argv) < 2:
        print ("Please enter the ip address or 'dhcp' for this server on the command line.")
        print ("Examples:  {0} 10.1.1.12   or   {0} dhcp").format(argv[0])
        exit()
    
    if argv[1].lower() == "dhcp":
        target_data = build_dhcpfile()
    else:
        netdata = build_netdata(argv[1])
        target_data = build_netfile(netdata)

    write_data(target_data)

    print ("\nChanges completed.")
    print ("These changes will not take effect until the system is rebooted or the interface is reset.")

    reboot_server()

if __name__ == '__main__':
    main(sys.argv)