`/bin/sh: 1: python: not found` 当通过 docker 中的 cron 运行时

Question

I want to repeatedly call a script via cron in a docker container, but when I switch from one time execution to execution via cron the official python image suddenly can't seem to find python.

Dockerfile:

FROM python:3.7-slim

COPY main.py /home/main.py

#A: works
CMD [ "python", "/home/main.py" ]

#B: doesn't work
#RUN  apt-get update && apt-get -y install -qq --force-yes cron
#COPY hello-cron /etc/cron.d/hello-cron
#CMD ["cron", "-f"]

main.py

import time

for i in range(90000):
    print(i)
    time.sleep(5000)

hello-cron:

* * * * * root python /home/main.py > /proc/1/fd/1 2> /proc/1/fd/2
#

When I switch A for B in the Dockerfile the error message is: /bin/sh: 1: python: not found

Thank you all for he quick responses! Adding PATH=/usr/local/bin in the cron file solved my problem.

Answer 1

Cron doesn't set up the PATH environment variable the same as a normal login shell so python can't be found. It should work if you specify a complete path to the Python executable, eg replace python with /usr/bin/python (or whatever the path to your Python executable happens to be). Alternatively you can explicitly set the PATH environment variable in the Cron configuration file to include the directory where Python can be found.