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✏️ Editing: qemu_nbd.py

"""
Qemu Command Wrapper

The qemu system comes with powerful tools, such as qemu-img and qemu-nbd which
are used here to build up kvm images.
"""

import glob
import logging
import os
import tempfile
import time

import salt.crypt
import salt.utils.path

# Set up logging
log = logging.getLogger(__name__)

def __virtual__():
    """
    Only load if qemu-img and qemu-nbd are installed
    """
    if salt.utils.path.which("qemu-nbd"):
        return "qemu_nbd"
    return (
        False,
        "The qemu_nbd execution module cannot be loaded: the qemu-nbd binary is not in"
        " the path.",
    )

def connect(image):
    """
    Activate nbd for an image file.

CLI Example:

.. code-block:: bash

salt '*' qemu_nbd.connect /tmp/image.raw
    """
    if not os.path.isfile(image):
        log.warning("Could not connect image: %s does not exist", image)
        return ""

if salt.utils.path.which("sfdisk"):
        fdisk = "sfdisk -d"
    else:
        fdisk = "fdisk -l"
    __salt__["cmd.run"]("modprobe nbd max_part=63")
    for nbd in glob.glob("/dev/nbd?"):
        if __salt__["cmd.retcode"](f"{fdisk} {nbd}"):
            while True:
                # Sometimes nbd does not "take hold", loop until we can verify
                __salt__["cmd.run"](
                    f"qemu-nbd -c {nbd} {image}",
                    python_shell=False,
                )
                if not __salt__["cmd.retcode"](f"{fdisk} {nbd}"):
                    break
            return nbd
    log.warning("Could not connect image: %s", image)
    return ""

def mount(nbd, root=None):
    """
    Pass in the nbd connection device location, mount all partitions and return
    a dict of mount points

CLI Example:

.. code-block:: bash

salt '*' qemu_nbd.mount /dev/nbd0
    """
    __salt__["cmd.run"](
        f"partprobe {nbd}",
        python_shell=False,
    )
    ret = {}
    if root is None:
        root = os.path.join(tempfile.gettempdir(), "nbd", os.path.basename(nbd))
    for part in glob.glob(f"{nbd}p*"):
        m_pt = os.path.join(root, os.path.basename(part))
        time.sleep(1)
        mnt = __salt__["mount.mount"](m_pt, part, True)
        if mnt is not True:
            continue
        ret[m_pt] = part
    return ret

def init(image, root=None):
    """
    Mount the named image via qemu-nbd and return the mounted roots

CLI Example:

.. code-block:: bash

salt '*' qemu_nbd.init /srv/image.qcow2
    """
    nbd = connect(image)
    if not nbd:
        return ""
    return mount(nbd, root)

def clear(mnt):
    """
    Pass in the mnt dict returned from nbd_mount to unmount and disconnect
    the image from nbd. If all of the partitions are unmounted return an
    empty dict, otherwise return a dict containing the still mounted
    partitions

CLI Example:

.. code-block:: bash

salt '*' qemu_nbd.clear '{"/mnt/foo": "/dev/nbd0p1"}'
    """
    ret = {}
    nbds = set()
    for m_pt, dev in mnt.items():
        mnt_ret = __salt__["mount.umount"](m_pt)
        if mnt_ret is not True:
            ret[m_pt] = dev
        nbds.add(dev[: dev.rindex("p")])
    if ret:
        return ret
    for nbd in nbds:
        __salt__["cmd.run"](f"qemu-nbd -d {nbd}", python_shell=False)
    return ret

MR SKB