Docker refusing to run bash

Question

I have the following docker setup:

python27.Dockerfile

FROM python:2.7
COPY ./entrypoint.sh /entrypoint.sh
RUN mkdir /src
RUN apt-get update && apt-get install -y bash libmysqlclient-dev python-pip build-essential && pip install virtualenv
ENTRYPOINT ["/entrypoint.sh"]
EXPOSE 8000
WORKDIR /src
CMD source /src/env/bin/activate && python /src/manage.py runserver

entrypoint.sh

#!/bin/bash

# some code here...
# some code here...
# some code here...

exec "$@"

Whenever I try to run my docker container I get python27 | /bin/sh: 1: source: not found.

I understand that the error comes from the fact that the command is run with sh instead of bash, but I can't understand why is that happening, given the fact that I have the correct shebang at the top of my entrypoint.

Any ideas why is that happening and how can I fix it?

@johnharris85 Yes, I'm installing it in the 4th line in my Dockerfile. — Alexander Nestorov
– Alexander Nestorov, Commented May 7, 2017 at 17:00

Ricardo Branco · Accepted Answer · 2017-05-12 16:40:01Z

2

The problem is that for CMD you're using the shell form that uses /bin/sh, and the /src/env/bin/activate likely contains a "source" command, which isn't available on POSIX /bin/sh (the equivalent builtin would be just .).

You must use the exec form for CMD using brackets:

CMD ["/bin/bash", "-c", "source /src/env/bin/activate && python /src/manage.py runserver"]

More details in:

edited May 12, 2017 at 16:40

answered May 7, 2017 at 17:00

Ricardo Branco

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3 Comments

Alexander Nestorov Over a year ago

Yes, that work. But I still can't understand why is this happening. I mean, the entrypoint get's executed with the command (as arguments) of the CMD. The entrypoint executes exec '$@', which is basically exec source ..... && python ...., and all that inside bash. So why is the source part failing?

Ricardo Branco Over a year ago

See the last part of the last link of my response, on the result of the multiple different ENTRYPOINT / CMD combinations. In your case, it would be: /entrypoint.sh /bin/sh -c source ...

Ricardo Branco Over a year ago

PD: By exec form they mean using the exec*() system calls and not the exec builtin shell command.

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