Generate configdrive suitable for ironic in pure Python

genconfigdrive.py

#!/usr/bin/env python

import base64
import contextlib
import gzip
import os
import sys
import StringIO

import pycdlib  # GNU LGPL v2.1 - not possible to include in Apache 2.0-licensed code :(

"""Generate configdrive from prepared on-disk directory."""

# This should be possible to generalize and populate the iso from filenames and their content
# w/o reading them from disk, purely from Python data structure of lists/dicts/strings
def populate_iso(dirname, iso):
    for root, dirs, files in os.walk(dirname, topdown=True):
        relroot = os.path.relpath(root, dirname)
        if relroot == '.':
            relroot = ''
        for d in dirs:
            iso.add_directory('/%s' % os.path.join(relroot, d),
                              rr_name=d,
                              joliet_path='/%s' % os.path.join(relroot, d))
        for f in files:
            iso.add_file(os.path.join(root, f),
                         '/%s.;1' % os.path.join(relroot, f),
                         rr_name=f,
                         joliet_path='/%s' % os.path.join(relroot, f))


def create_iso(dirname, fileobj):
    with contextlib.closing(pycdlib.PyCdlib()) as iso:
        # these settings are mostly copied from 'genisoimage' arguments OpenStack Nova uses
        # to create the configdrive ISO
        # maximum interchange_level is choosen to hopefully accomodate for some of those options
        # (leading dots etc).
        # Volume label is what configdrive is expected to have by cloud-init,
        # but currently mounting this shows volume label padded with some symbols.
        iso.new(interchange_level=4,
                joliet=True,
                rock_ridge='1.09',
                vol_ident='config-2')
        populate_iso(dirname, iso)
        iso.write_fp(fileobj)


def create_configdrive(dirname, outfile):
    """Create a configdrive from directory.
    
    The resulting file is written in base64-encoded gzipped ISO format
    suitable to paste into instance_info of ironic node or
    to serving it from HTTP for the same sake.
    """
    with contextlib.closing(StringIO.StringIO()) as gzip_fp:
        with gzip.GzipFile(fileobj=gzip_fp, mode='w') as g:
            with contextlib.closing(StringIO.StringIO()) as iso_fp:
                create_iso(dirname, iso_fp)
                g.write(iso_fp.getvalue())
        with open(outfile, 'w') as out:
            out.write(base64.b64encode(gzip_fp.getvalue()))

            
def main():
    if len(sys.argv) != 3:
        print('Usage: %s <DIRNAME> <OUTPUT-FILE-NAME>' % sys.argv[0])
        exit(1)
    create_configdrive(*sys.argv[1:])


if __name__ == '__main__':
    main()