1

"""

     2

    Mount filesystems.

     3

"""

     4

     5

from pvl.backup.invoke import command

     6

     7

import contextlib

     8

import os.path

     9

import logging

    10

    11

log = logging.getLogger('pvl.backup.mount')

    12

    13

    14

class MountError (Exception) :

    15

    pass

    16

    17

class Mount (object) :

    18

    """

    19

        Trivial filesystem mounting

    20

    """

    21

    22

    MOUNT   = '/bin/mount'

    23

    UMOUNT  = '/bin/umount'

    24

    25

    26

    def __init__ (self, dev, mnt, readonly=False) :

    27

        """

    28

            dev         - device path

    29

            mnt         - mount path

    30

            readonly    - mount readonly

    31

        """

    32

    33

        self.dev = dev

    34

        self.mnt = mnt

    35

        self.readonly = readonly

    36

    37

    @property

    38

    def path (self) :

    39

        return self.mnt

    40

    41

    def options (self) :

    42

        """

    43

            Mount options as a comma-separated string.

    44

        """

    45

    46

        options = [

    47

                ('ro' if self.readonly else None),

    48

        ]

    49

    50

        return ','.join(option for option in options if option)

    51

    52

    def open (self) :

    53

        """

    54

            Mount

    55

        """

    56

    57

        # check

    58

        if not os.path.isdir(self.mnt) :

    59

            raise MountError("Mountpoint is not a directory: {mnt}".format(mnt=self.mnt))

    60

    61

        if os.path.ismount(self.mnt) :

    62

            raise MountError("Mountpoint is already mounted: {mnt}".format(mnt=self.mnt))

    63

    64

        if not os.path.exists(self.dev) :

    65

            raise MountError("Device does not exist: {dev}".format(dev=self.dev))

    66

    67

        # mount

    68

        command(self.MOUNT, self.dev, self.mnt, options=self.options())

    69

    70

    def close (self) :

    71

        """

    72

            Un-mount

    73

        """

    74

    75

        # check

    76

        if not os.path.ismount(self.mnt):

    77

            raise MountError("Mountpoint is not mounted: {mnt}".format(mnt=self.mnt))

    78

    79

        # umount

    80

        command(self.UMOUNT, self.mnt)

    81

    91

@contextlib.contextmanager

    92

def mount (dev, mnt, **kwargs) :

    93

    """

    94

        Use a temporary mount:

    95

    96

        with mount('/dev/...', '/mnt', readonly=True) as mount:

    97

            ...

    98

    """

    99

   100

    mount = Mount(dev, mnt, **kwargs)

   101

   102

    # open

   103

    log.debug("open: %s", mount)

   104

    mount.open()

   105

   106

    try :

   107

        log.debug("got: %s", mount)

   108

        yield mount

   109

   110

    finally:

   111

        # cleanup

   112

        log.debug("cleanup: %s", mount)

   113

        mount.close()

   114

   115