cloud-init: Can write_files be merged? - cloud-init

Question

Can write_files be merged? I can't seem to get the merge_how syntax correct. Only files in the last write_files are being created.
Thanks

Answer 1

The answer is yes.
When working with multi-part MIME, you must add the following to the header of each part.
Merge-Type: list(append)+dict(no_replace,recurse_list)+str()
Below is a modified version of the helper script provided in the cloud-init documentation.
#!/usr/bin/env python3
import click
import sys
import gzip as gz
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
#click.command()
#click.option('--gzip', is_flag=True,
help='gzip MIME message to current directory')
#click.argument('message', nargs=-1)
def main(message: str, gzip: bool) -> None:
"""This script creates a multi part MIME suitable for cloud-init
A MESSAGE has following format <filename>:<type> where <filename> is the
file that contains the data to add to the MIME message. <type> is the
MIME content-type.
MIME content-type may be on of the following:
text/cloud-boothook
text/cloud-config
text/cloud-config-archive
text/jinja2
text/part-handler
text/upstart-job
text/x-include-once-url
text/x-include-url
text/x-shellscript
EXAMPLE:
write-mime-multipart afile.cfg:cloud-config bfile.sh:x-shellscript
"""
combined_message = MIMEMultipart()
for message_part in message:
(filename, format_type) = message_part.split(':', 1)
with open(filename) as fh:
contents = fh.read()
sub_message = MIMEText(contents, format_type, sys.getdefaultencoding())
sub_message.add_header('Content-Disposition',
'attachment; filename="{}"'.format(filename))
sub_message.add_header('Merge-Type',
'list(append)+dict(no_replace,recurse_list)+str()')
combined_message.attach(sub_message)
if gzip:
with gz.open('combined-userdata.txt.gz', 'wb') as fd:
fd.write(bytes(combined_message))
else:
print(combined_message)
if __name__ == '__main__':
main()