COT.helpers.api module

API for abstract access to third-party helper tools.

Abstracts away operations that require third-party helper programs, especially those that are not available through PyPI.

The actual helper programs are provided by individual classes in this package.

Functions

convert_disk_image Convert the given disk image to the requested format/subformat.
create_disk_image Create a new disk image at the requested location.
create_install_dir Check whether the given target directory exists, and create if not.
download_and_expand Context manager for downloading and expanding a .tar.gz file.
get_checksum Get the checksum of the given file.
get_disk_capacity Get the storage capacity of the given disk image.
get_disk_format Get the disk image format of the given file.
install_file Copy the given src to the given dest, using sudo if needed.
convert_disk_image(file_path, output_dir, new_format, new_subformat=None)[source]

Convert the given disk image to the requested format/subformat.

If the disk is already in this format then it is unchanged; otherwise, will convert to a new disk in the specified output_dir and return its path.

Current supported conversions:

  • .vmdk (any format) to .vmdk (streamOptimized)
  • .img to .vmdk (streamOptimized)
Parameters:
  • file_path (str) – Disk image file to inspect/convert
  • output_dir (str) – Directory to place converted image into, if needed
  • new_format (str) – Desired final format
  • new_subformat (str) – Desired final subformat
Returns:

  • file_path, if no conversion was required
  • or a file path in output_dir containing the converted image
Raises:

ValueUnsupportedError – if the new_format and/or new_subformat are not supported conversion targets.
create_disk_image(file_path, file_format=None, capacity=None, contents=None)[source]

Create a new disk image at the requested location.

Either capacity or contents or both must be specified.

Parameters:
  • file_path (str) – Desired location of new disk image
  • file_format (str) – Desired image format (if not specified, this will be derived from the file extension of file_path)
  • capacity – Disk capacity. A string like ‘16M’ or ‘1G’.
  • contents (list) – List of file paths to package into the created image. If not specified, the image will be left blank and unformatted.
create_install_dir(directory, permissions=493)[source]

Check whether the given target directory exists, and create if not.

Parameters:
  • directory (str) – Directory to check/create.
  • permissions (int) – Permissions bits to set on the directory.
Returns:

True
download_and_expand(*args, **kwds)[source]

Context manager for downloading and expanding a .tar.gz file.

Creates a temporary directory, downloads the specified URL into the directory, unzips and untars the file into this directory, then yields to the given block. When the block exits, the temporary directory and its contents are deleted.

with download_and_expand("http://example.com/foo.tgz") as d:
    # archive contents have been extracted to 'd'
    ...
# d is automatically cleaned up.
Parameters:url (str) – URL of a .tgz or .tar.gz file to download.
get_checksum(path_or_obj, checksum_type)[source]

Get the checksum of the given file.

Parameters:
  • path_or_obj (str) – File path to checksum OR an opened file object
  • checksum_type (str) – Supported values are ‘md5’ and ‘sha1’.
Returns:

String containing hexadecimal file checksum
get_disk_capacity(file_path)[source]

Get the storage capacity of the given disk image.

Parameters:file_path (str) – Path to disk image file to inspect
Returns:Disk capacity, in bytes
get_disk_format(file_path)[source]

Get the disk image format of the given file.

Warning

If file_path refers to a file which is not a disk image at all, this function will return ('raw', None).

Parameters:file_path (str) – Path to disk image file to inspect.
Returns:(format, subformat)
  • format may be 'vmdk', 'raw', or 'qcow2'
  • subformat may be None, or various strings for 'vmdk' files.
install_file(src, dest)[source]

Copy the given src to the given dest, using sudo if needed.

Parameters:
  • src (str) – Source path.
  • dest (str) – Destination path.
Returns:

True