#!/usr/bin/python

import os, os.path

def st_dev_to_devicename(st_dev):
    '''Try to convert st_dev to a devicename by walking /sys/block.
    Yes, this will only work for block devices. Yes, that's intentional.'''
    (major,minor) = (os.major(st_dev),os.minor(st_dev))
    for root, dirs, files in os.walk('/sys/block',topdown=True):
        if root == '/sys/block': continue
        if 'dev' in files:
            dev_f = open(root+'/dev')
            dev = dev_f.readline().strip()
            dev_f.close()
        else:
            continue
        if not dev.startswith('%s:' % major):
            del dirs[:] 
        elif dev == "%s:%s" % (major,minor):
            return os.path.basename(root)
    return None


fn = 'images/stage2.img'
bootpath='/boot/upgrade'
somepath = bootpath + '/' + os.path.basename(fn)
st_dev = os.stat(somepath).st_dev
bootdev = st_dev_to_devicename(st_dev)
mtab = open("/etc/mtab")
mountpoint = ''
for line in mtab:
    (dev,mp,rest) = line.split(' ',2)
    if dev.endswith(bootdev):
        mountpoint = mp
if mountpoint:
    print '(%s, %s)' % (bootdev,somepath.replace(mountpoint,''))