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diff --git a/src/virtBootstrap/utils.py b/src/virtBootstrap/utils.py
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+++ b/src/virtBootstrap/utils.py
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+# Authors:
+#   Cedric Bosdonnat <cbosdonnat@suse.com>
+#   Radostin Stoyanov <rstoyanov1@gmail.com>
+#
+# Copyright (C) 2017 SUSE, Inc.
+# Copyright (c) 2017 Radostin Stoyanov
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program 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 General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+Module which contains utility functions used by virt-bootstrap.
+"""
+
+import errno
+import fcntl
+import hashlib
+import json
+import os
+import sys
+import tempfile
+import logging
+
+from subprocess import CalledProcessError, PIPE, Popen
+
+# pylint: disable=invalid-name
+# Create logger
+logger = logging.getLogger(__name__)
+# Default virtual size of qcow2 image
+DEF_QCOW2_SIZE = '5G'
+if os.geteuid() == 0:
+    LIBVIRT_CONN = "lxc:///"
+    DEFAULT_IMG_DIR = "/var/lib/virt-bootstrap/docker_images"
+else:
+    LIBVIRT_CONN = "qemu:///session"
+    DEFAULT_IMG_DIR = os.environ['HOME']
+    DEFAULT_IMG_DIR += "/.local/share/virt-bootstrap/docker_images"
+
+
+def checksum(path, sum_type, sum_expected):
+    """
+    Validate file using checksum.
+    """
+    algorithm = getattr(hashlib, sum_type)
+    try:
+        handle = open(path, 'rb')
+        content = handle.read()
+        handle.close()
+
+        actual = algorithm(content).hexdigest()
+        if not actual == sum_expected:
+            logger.warning("File '%s' has invalid hash sum.\nExpected: %s\n"
+                           "Actual: %s", path, sum_expected, actual)
+            return False
+        return True
+    except Exception as err:
+        logger.warning("Error occured while validating "
+                       "the hash sum of file: %s\n%s", path, err)
+        return False
+
+
+def execute(cmd):
+    """
+    Execute command and log debug message.
+    """
+    cmd_str = ' '.join(cmd)
+    logger.debug("Call command:\n%s", cmd_str)
+
+    proc = Popen(cmd, stdout=PIPE, stderr=PIPE)
+    output, err = proc.communicate()
+
+    if output:
+        logger.debug("Stdout:\n%s", output)
+    if err:
+        logger.debug("Stderr:\n%s", err)
+
+    if proc.returncode != 0:
+        raise CalledProcessError(proc.returncode, cmd_str)
+
+
+def safe_untar(src, dest):
+    """
+    Extract tarball within LXC container for safety.
+    """
+    virt_sandbox = ['virt-sandbox',
+                    '-c', LIBVIRT_CONN,
+                    '-m', 'host-bind:/mnt=' + dest]  # Bind destination folder
+
+    # Compression type is auto detected from tar
+    # Exclude files under /dev to avoid "Cannot mknod: Operation not permitted"
+    params = ['--', '/bin/tar', 'xf', src, '-C', '/mnt', '--exclude', 'dev/*']
+    execute(virt_sandbox + params)
+
+
+def format_number(number):
+    """
+    Turn numbers into human-readable metric-like numbers
+    """
+    symbols = ['', 'KiB', 'MiB', 'GiB']
+    step = 1024.0
+    thresh = 999
+    depth = 0
+    max_depth = len(symbols) - 1
+
+    while number > thresh and depth < max_depth:
+        depth = depth + 1
+        number = number / step
+
+    if int(number) == float(number):
+        fmt = '%i %s'
+    else:
+        fmt = '%.2f %s'
+
+    return(fmt % (number or 0, symbols[depth]))
+
+
+def size_to_bytes(string, fmt):
+    """
+    Convert human readable formats to bytes.
+    """
+    formats = {'B': 0, 'KB': 1, 'MB': 2, 'GB': 3, 'TB': 4}
+    return (string * pow(1024, formats[fmt.upper()]) if fmt in formats
+            else False)
+
+
+def log_layer_extract(layer, current, total, progress):
+    """
+    Create log message on layer extract.
+    """
+    sum_type, sum_value, layer_file, layer_size = layer
+    progress("Extracting layer (%s/%s) with size: %s"
+             % (current, total, format_number(layer_size)), logger=logger)
+    logger.debug('Untar layer: (%s:%s) %s', sum_type, sum_value, layer_file)
+
+
+def untar_layers(layers_list, dest_dir, progress):
+    """
+    Untar each of layers from container image.
+    """
+    nlayers = len(layers_list)
+    for index, layer in enumerate(layers_list):
+        log_layer_extract(layer, index + 1, nlayers, progress)
+        layer_file = layer[2]
+
+        # Extract layer tarball into destination directory
+        safe_untar(layer_file, dest_dir)
+
+        # Update progress value
+        progress(value=(float(index + 1) / nlayers * 50) + 50)
+
+
+def get_mime_type(path):
+    """
+        Get the mime type of a file.
+    """
+    return Popen(["/usr/bin/file", "--mime-type", path],
+                 stdout=PIPE).communicate()[0].split()[1]
+
+
+def create_qcow2(tar_file, layer_file, backing_file=None, size=DEF_QCOW2_SIZE):
+    """
+    Create qcow2 image from tarball.
+    """
+    qemu_img_cmd = ["qemu-img", "create", "-f", "qcow2", layer_file, size]
+
+    if not backing_file:
+        logger.info("Creating base qcow2 image")
+        execute(qemu_img_cmd)
+
+        logger.info("Formatting qcow2 image")
+        execute(['virt-format',
+                 '--format=qcow2',
+                 '--partition=none',
+                 '--filesystem=ext3',
+                 '-a', layer_file])
+    else:
+        # Add backing chain
+        qemu_img_cmd.insert(2, "-b")
+        qemu_img_cmd.insert(3, backing_file)
+
+        logger.info("Creating qcow2 image with backing chain")
+        execute(qemu_img_cmd)
+
+    # Get mime type of archive
+    mime_tar_file = get_mime_type(tar_file)
+    logger.debug("Detected mime type of archive: %s", mime_tar_file)
+
+    # Extract tarball using "tar-in" command from libguestfs
+    tar_in_cmd = ["guestfish",
+                  "-a", layer_file,
+                  '-m', '/dev/sda',
+                  'tar-in', tar_file, "/"]
+
+    compression_fmts = {'x-gzip': 'gzip', 'gzip': 'gzip',
+                        'x-xz': 'xz',
+                        'x-bzip2': 'bzip2',
+                        'x-compress': 'compress',
+                        'x-lzop': 'lzop'}
+
+    # Check if tarball is compressed
+    mime_parts = mime_tar_file.split('/')
+    if mime_parts[0] == 'application' and \
+       mime_parts[1] in compression_fmts:
+        tar_in_cmd.append('compress:' + compression_fmts[mime_parts[1]])
+
+    # Execute virt-tar-in command
+    execute(tar_in_cmd)
+
+
+def extract_layers_in_qcow2(layers_list, dest_dir, progress):
+    """
+    Extract docker layers in qcow2 images with backing chains.
+    """
+    qcow2_backing_file = None
+
+    nlayers = len(layers_list)
+    for index, layer in enumerate(layers_list):
+        log_layer_extract(layer, index + 1, nlayers, progress)
+        tar_file = layer[2]
+
+        # Name format for the qcow2 image
+        qcow2_layer_file = "{}/layer-{}.qcow2".format(dest_dir, index)
+        # Create the image layer
+        create_qcow2(tar_file, qcow2_layer_file, qcow2_backing_file)
+        # Keep the file path for the next layer
+        qcow2_backing_file = qcow2_layer_file
+
+        # Update progress value
+        progress(value=(float(index + 1) / nlayers * 50) + 50)
+
+
+def get_image_dir(no_cache=False):
+    """
+    Get the directory where image layers are stored.
+
+    @param no_cache: Boolean, indicates whether to use temporary directory
+    """
+    if no_cache:
+        return tempfile.mkdtemp('virt-bootstrap')
+
+    if not os.path.exists(DEFAULT_IMG_DIR):
+        os.makedirs(DEFAULT_IMG_DIR)
+
+    return DEFAULT_IMG_DIR
+
+
+def get_image_details(src, raw=False,
+                      insecure=False, username=False, password=False):
+    """
+    Return details of container image from "skopeo inspect" commnad.
+    """
+    cmd = ['skopeo', 'inspect', src]
+    if raw:
+        cmd.append('--raw')
+    if insecure:
+        cmd.append('--tls-verify=false')
+    if username and password:
+        cmd.append("--creds=%s:%s" % (username, password))
+    proc = Popen(cmd, stdout=PIPE, stderr=PIPE)
+    output, error = proc.communicate()
+    if error:
+        raise ValueError("Image could not be retrieved:", error)
+    return json.loads(output)
+
+
+def is_new_layer_message(line):
+    """
+    Return T/F whether a line in skopeo's progress is indicating
+    start the process of new image layer.
+
+    Reference:
+    - https://github.com/containers/image/blob/master/copy/copy.go#L464
+    - https://github.com/containers/image/blob/master/copy/copy.go#L459
+    """
+    return line.startswith('Copying blob') or line.startswith('Skipping fetch')
+
+
+def is_layer_config_message(line):
+    """
+    Return T/F indicating whether the message from skopeo copies the manifest
+    file.
+
+    Reference:
+    - https://github.com/containers/image/blob/master/copy/copy.go#L414
+    """
+    return line.startswith('Copying config')
+
+
+def make_async(fd):
+    """
+    Add the O_NONBLOCK flag to a file descriptor.
+    """
+    fcntl.fcntl(fd, fcntl.F_SETFL,
+                fcntl.fcntl(fd, fcntl.F_GETFL) | os.O_NONBLOCK)
+
+
+def read_async(fd):
+    """
+    Read some data from a file descriptor, ignoring EAGAIN errors
+    """
+    try:
+        return fd.read()
+    except IOError as e:
+        if e.errno != errno.EAGAIN:
+            raise
+        else:
+            return ''
+
+
+def str2float(element):
+    """
+    Convert string to float or return None.
+    """
+    try:
+        return float(element)
+    except ValueError:
+        return None
+
+
+def write_progress(prog):
+    """
+    Write progress output to console
+    """
+    # Get terminal width
+    try:
+        terminal_width = int(Popen(["stty", "size"], stdout=PIPE).stdout
+                             .read().split()[1])
+    except Exception:
+        terminal_width = 80
+    # Prepare message
+    msg = "\rStatus: %s, Progress: %.2f%%" % (prog['status'], prog['value'])
+    # Fill with whitespace and return cursor at the begging
+    msg = "%s\r" % msg.ljust(terminal_width)
+    # Write message to console
+    sys.stdout.write(msg)
+    sys.stdout.flush()