Pass environment variables in a dockerfile with a script

Question

I'm starting to use Docker and I'm making a webservice using Flask. In order to connect to databases I need to tell the service the credentials to connect. I don't want to put the variable directly on the Dockerfile or worst, on code. I thought of passing them through environment variables that are set on build time via a shell script called on the Dockerfile.

The thing here is that I've tried using CMD,RUN and ENTRYPOINT to achieve this without success.

Here's the last version of my Dockerfile:

FROM python:2.7-slim


WORKDIR /app
ADD . /app



RUN pip install --upgrade pip
RUN pip install -r requirements.txt
EXPOSE 5000



ENTRYPOINT ["python"]
CMD ["/app/con.sh"]
CMD ["-u","app.py"]

The script is named con.sh and has a structure like this:

export REDSHIFT_HOST="[Host of the DB]"
export REDSHIFT_USER="[DB user]"
export REDSHIFT_PASSWD="[DB password]"
export POSTGRES_DB="[DB name]"
export MODEL_IP="[endpoint of another service]"
export USER_SF="[user]"
export PASS_SF="[pass]"
export TOKEN="[Token]"
export INSTANCE_URL="[URL]"

What I get from this is:

    Traceback (most recent call last):
  File "app.py", line 4, in <module>
    from clean_leads import *
  File "/app/clean_leads.py", line 13, in <module>
    HOST = os.environ['REDSHIFT_HOST']
  File "/usr/local/lib/python2.7/UserDict.py", line 40, in __getitem__
    raise KeyError(key)
KeyError: 'REDSHIFT_HOST'

Which confirms that the environment variables didn't get set.

Did you try `setenv REDSHIFT_HOST "[HOSTOF DB]" – user1767754 Nov 27 '17 at 19:04 — user1767754, Nov 27 '17 at 19:04

score 1 · Accepted Answer · answered Nov 27 '17 at 19:16

You have two CMD statements in your Dockerfile, which isn't going to work. You can only have 1 CMD statement, so your last one is going to overwrite the first.

From the Docker documentation:

There can only be one CMD instruction in a Dockerfile. If you list more than one CMD then only the last CMD will take effect.

You'll need to combine your CMDs into a single statement.

See here: Execute a script before CMD

score 0 · Answer 2 · answered Nov 27 '17 at 19:11

0

You seem to be looking for an .env file.

Create a file in the format <variable>=value with the variables you want to set.

REDSHIFT_HOST="[Host of the DB]"
REDSHIFT_USER="[DB user]"
REDSHIFT_PASSWD="[DB password]"
# ...

Then pass it to your run command with the --env-file option (name it .env for instance):

sudo docker run --rm -ti --env-file .env alpine sh

You can then check the output of echo $REDSHIFT_HOST:

"[Host of the DB]"

Also, take a look at this part of the docs.

answered Nov 27 '17 at 19:11

grovina

2,999
19
25

That should work, but i wanted to do it on build time since I plan on deploying it into gcloud's container engine and I don't know if its possible to tell kubernets to set the environment variables and less to make it from a file – Dudley Díaz Nov 28 '17 at 19:14

Pass environment variables in a dockerfile with a script

2 Answers2