How to read and write files with Flask with Ubuntu and apache server

Question

I am trying to deploy an app that writes and reads png images with Flask. Locally I can run my script with no errors, except when I run it on my server.

I deployed using this guide on DigitalOcean. It uses apache, wsgi and virtualenv.

This an example of my code:

from flask import Flask
from flask import send_file
from PIL import Image

app = Flask(__name__)

@app.route("/")
def hello():
    img = Image.new('RGB', (200, 100), (255, 255, 255))
    img.save('output.png')
    return send_file('output.png', mimetype='image/png')

if __name__ == "__main__":
    app.run()

I found out that what is causing the problem is img.save('output.png') I found also that if I try to load a font like: font = ImageFont.truetype("Archive.otf", 60) it doesn't work neither. My .png and .otf files are in the same folder as __init__.py

I guess I am messing up with the configuration or the directrory paths of apache. If I run img.save outside the flask enviroment it works, so it is not a problem with libraries or dependencies.

What happens if you provide absolute path to img.save like img.save("/srv/my/server/path/output.png") (of course, the correspoding dir should exists and your Apache have to have enough rights to write there)? — Ilya V. Schurov
– Ilya V. Schurov, Commented Nov 26, 2016 at 15:11
I found out the main problem is that apache or python does not have the rights to write and read files. I am trying to figure out how to do that but without success yet. — Domingo
– Domingo, Commented Nov 26, 2016 at 18:26

Leonora Tindall · Accepted Answer · 2016-11-26 15:15:34Z

2

You need to use an absolute path, like /var/www/somedir/somefile. This is because Flask under Apache does not give Python a usable working directory. I would suggest making the path configurable.

answered Nov 26, 2016 at 15:15

Leonora Tindall

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2 Comments

Domingo Over a year ago

I only managed to save the files in /tmp, I think I need to give apache/python the rights to read and write files, but I am having trouble for that too.

Leonora Tindall Over a year ago

You need to make sure that the Apache user has read/write access to the directories you're trying to use.

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