reswap.py

#!/usr/bin/env python

"""
mostly-hot-resize a swap device from a Xen VM.
(Py 2/3)

usage:
vm  # swapoff -a
host# ./reswap.py /etc/xen/vmname.cfg xvda1 1g
vm  # swapon -a
"""

import os
import sys
import imp
import subprocess

if sys.version_info[:2] <= (2, 7):
    input = raw_input

if len(sys.argv) != 4:
    print("usage: reswap.py <config path> <device name> <new_size>")
    exit(1)

vm_cfg = imp.load_source('cfg', sys.argv[1])
device = sys.argv[2]
new_size = sys.argv[3]

name = vm_cfg.name
print("vm name: %s" % name)

swap_config = ''
swap_file = ''
for d in vm_cfg.disk:
    parts = d.split(',')
    if parts[1] == device:
        assert parts[0].startswith('file:')
        swap_config = d
        swap_file = parts[0][5:]  # skip file:
        break
else:
    print("swap device not found.")
    exit(1)

print("swap: %s (%s)" % (swap_file, swap_config))

blklist = subprocess.check_output(['xl', 'block-list', name])
blklist = blklist.split('\n')
blklist = [l.split() for l in blklist]
blklist = [(p[0], p[6]) for p in blklist[1:] if p]

for blkn, blkpath in blklist:
    blkdev = subprocess.check_output(['xenstore-read', blkpath + '/dev']).strip()
    if blkdev == device:
        break
else:
    print("block device not found")
    exit(1)

print("blk: %s (%s) -> %s" % (blkn, blkdev, blkpath))
print(subprocess.check_output(['xenstore-ls', blkpath]))

print(" ---- ")
print("okay? [y] (SWAPOFF FIRST!)")
if input() != 'y':
    print("aborted")
    exit(1)

def run_print(args):
    print(">" + " ".join(args))
    print(subprocess.check_output(args))

run_print(['xl', 'block-detach', name, blkn])
run_print(['truncate', '-s', new_size, swap_file])
run_print(['mkswap', swap_file])
run_print(['xl', 'block-attach', name, swap_config])

print(" ---- ")
print("done, you can swapon -a")