Setup script for dnsmasq on sandbox

dnsmasq-setup.py

#!/usr/bin/python
#
# Sandbox dnsmasq setup script
# 
# Jak Spalding <jak.spalding@bbc.co.uk>
# 2012-03-03
#
# for Python 2.4

import re
import subprocess
import os.path
import shutil
import sys

def main():
	checkifroot()
	print '************************'
	print '* dnsmasq setup script *'
	print '************************'
	ip = raw_input('What is the IP address you want to use (e.g. 192.168.1.7)?\n');
	print 'Checking IP address format...',
	checkip(ip)
	print 'Checking that dnsmasq is installed...',
	checkdnsmasq()
	print 'Adding dnsmasq hosts file (using %s)...' % ip,
	addhostsfile(ip)
	print 'Adding dnsmasq configuration...',
	addconfig()
	print 'Attempting to add dnsmasq to system startup...',
	addstartup()
	print 'Starting dnsmasq service...'
	startdnsmasq()
	print '************************'
	print '*       all done!      *'
	print '************************'
	print 'You can now point your mobile device to use DNS server of', ip		

def checkip(ip):
	ret = re.match('(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)', ip)
	if ret == None:
		print "ERROR: That's not a valid IP address!"
		sys.exit(1)
	print 'OK'

def checkifroot():
	try: 
		user = subprocess.Popen(['whoami'], stdout=subprocess.PIPE).communicate()[0]
	except OSError:
		print 'ERROR: Unable to run whoami to check if user is running as root'
		sys.exit(1)
	user = user.strip()
	#print 'current user = %s' % user
	if user != 'root':
		print 'ERROR: You have to run this script as root.'
		sys.exit(1)

def checkdnsmasq():
	ret = 1
	try: 
		ret = subprocess.call(['dnsmasq','-v'], stderr=subprocess.STDOUT, stdout=subprocess.PIPE);
	except OSError:
		ret = 1
	if ret != 0:
		print "ERROR: Please install dnsmasq (e.g. yum install dnsmasq)!"
		sys.exit(1)
	print 'OK'

def addhostsfile(ip):
	fp = '/etc/dnsmasq.hosts'
	contents = '%s pal.sandbox.dev.bbc.co.uk static.sandbox.dev.bbc.co.uk' % ip

	if os.path.isfile(fp):
		print 'File %s exists.. overwriting' % fp

	f = open(fp, 'w')
	try:
		f.write(contents)
	finally:
		f.close()

	print 'OK'

def addconfig():
	fp = '/etc/dnsmasq.conf'
	contents = "no-hosts\naddn-hosts=/etc/dnsmasq.hosts"

	if os.path.isfile(fp):
		print 'Making a backup of', fp
		shutil.move(fp, fp + '.bak')

	f = open(fp, 'w')
	try:
		f.write(contents)
	finally:
		f.close()
	
	print 'OK'

def addstartup():
	ret = 1
	try: 
		ret = subprocess.call(['chkconfig','--level','3','dnsmasq','on'], stderr=subprocess.STDOUT, stdout=subprocess.PIPE);
	except OSError:
		ret = 1
	if ret != 0:
		print "ERROR: Failed to add dnsmasq to system startup! (Return value was %d)" % ret
		sys.exit(1)
	print 'OK'

def startdnsmasq():
	ret = 1
	try: 
		ret = subprocess.call(['service','dnsmasq','restart']);
	except OSError:
		ret = 1
	if ret != 0:
		print "ERROR: Failed to start dnsmasq... you'd better fix that!"
		sys.exit(1)	


try:
	main()
except KeyboardInterrupt:
	print 'Bye!'
sys.exit(0)