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"""

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    Mount filesystems.

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"""

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from pvl.backup.invoke import command

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import contextlib

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import logging

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

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class MountError (Exception) :

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    pass

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class Mount (object) :

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    """

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        Trivial filesystem mounting

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    """

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    MOUNT   = '/bin/mount'

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    UMOUNT  = '/bin/umount'

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

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        """

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            dev         - device path

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            mnt         - mount path

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            readonly    - mount readonly

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        """

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        self.dev = dev

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        self.mnt = mnt

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        self.readonly = readonly

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    @property

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    def path (self) :

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        return self.mnt

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    def options (self) :

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        """

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            Mount options as a comma-separated string.

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        """

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        options = [

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

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        ]

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

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    def open (self) :

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        """

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            Mount

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        """

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        # check

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

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

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

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

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

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

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        # mount

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

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    def close (self) :

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        """

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            Un-mount

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        """

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        # check

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

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

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        # umount

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        command(self.UMOUNT, self.mnt)

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    def __repr__ (self) :

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        return "Mount(dev={dev}, mnt={mnt})".format(

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                dev     = repr(self.dev),

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                mnt     = repr(self.mnt),

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        )

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    def __str__ (self) :

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        return self.mnt

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@contextlib.contextmanager

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    """

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        Use a temporary mount:

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            ...

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    """

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    try :

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    finally:

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