~james-page/charms/trusty/cinder/lp1516085-stable

# Copyright 2014-2015 Canonical Limited.

#

# This file is part of charm-helpers.

#

# charm-helpers is free software: you can redistribute it and/or modify

# it under the terms of the GNU Lesser General Public License version 3 as

# published by the Free Software Foundation.

#

# charm-helpers is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU Lesser General Public License for more details.

#

# You should have received a copy of the GNU Lesser General Public License

# along with charm-helpers.  If not, see <http://www.gnu.org/licenses/>.

import os

import re

from stat import S_ISBLK

from subprocess import (

    check_call,

    check_output,

    call

)

def is_block_device(path):

    '''

    Confirm device at path is a valid block device node.

    :returns: boolean: True if path is a block device, False if not.

    '''

    if not os.path.exists(path):

        return False

    return S_ISBLK(os.stat(path).st_mode)

def zap_disk(block_device):

    '''

    Clear a block device of partition table. Relies on sgdisk, which is

    installed as pat of the 'gdisk' package in Ubuntu.

    :param block_device: str: Full path of block device to clean.

    '''

    # sometimes sgdisk exits non-zero; this is OK, dd will clean up

    call(['sgdisk', '--zap-all', '--mbrtogpt',

          '--clear', block_device])

    dev_end = check_output(['blockdev', '--getsz',

                            block_device]).decode('UTF-8')

    gpt_end = int(dev_end.split()[0]) - 100

    check_call(['dd', 'if=/dev/zero', 'of=%s' % (block_device),

                'bs=1M', 'count=1'])

    check_call(['dd', 'if=/dev/zero', 'of=%s' % (block_device),

                'bs=512', 'count=100', 'seek=%s' % (gpt_end)])

def is_device_mounted(device):

    '''Given a device path, return True if that device is mounted, and False

    if it isn't.

    :param device: str: Full path of the device to check.

    :returns: boolean: True if the path represents a mounted device, False if

        it doesn't.

    '''

    is_partition = bool(re.search(r".*[0-9]+\b", device))

    out = check_output(['mount']).decode('UTF-8')

    if is_partition:

        return bool(re.search(device + r"\b", out))

    return bool(re.search(device + r"[0-9]*\b", out))