resize-vm-image.py

#!/usr/bin/python

# NOTE: We need the system wide Python(2.6) because that's where
#       the guestfs libs are installed (RHEL6.X)
#       rpm package python-libguestfs is required for this to work
#
#       yum install python-libguestfs
#
# Provide the disk image name as the only argument to this script
#

import guestfs
import sys, string

assert (len (sys.argv) == 2)
disk = sys.argv[1]

# For return values we want a dict object
g = guestfs.GuestFS (python_return_dict=True)

# Add our image
g.add_drive_opts (disk)

# Launch the guestfs back-end (same as run)
g.launch()

# Ask libguestfs to inspect for operating systems.
roots = g.inspect_os()
if len(roots) == 0:
    raise (Error ("inspect_vm: no operating systems found"))

# We should get one device back, likely /dev/sda
devs = g.list_devices()
if len(devs) == 1:
   dev = devs[0]
   print "Found one device: %s" % dev
else:
   print "Found more than one dev, please specify which one you want to operate on.."
   sys.exit(1)

# We are expecting 2 partitions back from this device
# 1st part is boot partition
# 2nd part is pvs with root.fs and swap.vol in it
partitions = g.part_list(dev)
if len(partitions) == 2:
   print "Found 2 partitions"
   # double check that 2nd part is actually #2 and get it's start location
   if partitions[1]['part_num'] == 2:
      part_start = partitions[1]['part_start']
      dev_part = dev + str(partitions[1]['part_num'])
   else:
      print "cant find 2nd partition to modify.."
      sys.exit(2)
else:
   print "expected 2 partitions found %i instead" % len(partitions)

# Get block size
blk_size = g.blockdev_getss(dev)
print "Block size: %i" % blk_size

# Calculate start sector
start_sector = part_start / blk_size
print "Caclulated start sector: %i" % start_sector

# Delete 2nd partition on image
if g.part_del(dev, 2):
   print "Parition delete failed.. Exiting"
   sys.exit(3)
print "Old partition removed"

# Flush device
print "Flushing buffers.."
g.blockdev_flushbufs(dev)

# Recreate 2nd partition -1 means last sector
# NOTE: This command will issue a warning about the kernel failing to re-read the part table, this is ok and expected
# Actually it returns -1 even though it succeeds
try:
  g.part_add(dev, 'p', start_sector, -1)
except RuntimeError as msg:
  print "Part add failed due to re-read of partition table, this is normal and expected.. Ignored.."

print "Partition created/expanded"

# Shutdown and restart guestfs to get our newly expanded partition table to be seen
print "Restarting guestfs (this takes a second)"
g.shutdown()
g.add_drive_opts(disk)
g.launch()

# Resize the PV
if g.pvresize(dev_part):
   print "pvresize failed.. Exiting"
   sys.exit(5)
print "pv resized"

# Find and resize our volumes now
vols = g.lvs()
for vol in vols:
   if string.find(string.split(vol, '/')[-1], "root.fs") >= 0:
      print "root vol is: %s" % vol
      root_vol = vol
   if string.find(string.split(vol, '/')[-1], "swap.vol") >= 0:
      print "swap vol is: %s" % vol
      swap_vol = vol

if g.lvresize(swap_vol, 6144):
   print "lvresize on swap failed.. Exiting"
   sys.exit(6)
print "lvresize on swap succeeded"

if g.lvresize_free(root_vol, 100):
   print "lvresize on root failed.. Exiting"
   sys.exit(7)
print "lvresize on root succeeded"

if g.resize2fs(root_vol):
   print "resize2fs on root vol failed.. Exiting"
   sys.exit(8)
print "resize2fs on root succeeded"

if g.e2fsck(root_vol, correct=True):
   print "e2fsck on root vol failed.. Exiting"
   sys.exit(9)
print "e2fsck on root succeeded"

print "Resize completed, go ahead and boot the vm now"
g.shutdown()
g.close()
sys.exit(0)