I am completely new to Docker and Linux and I am trying to make a simple Alpine based image that runs a cronjob every minute. That is, it should pint “Hello” every minute.
Steps to reproduce:
Make a docker file with the following content:
<code># Use an official Alpine image as a parent image
FROM alpine:latest
# Install cron and any other dependencies you might need
RUN apk update &&
apk add dcron wget curl logrotate
# Add crontab file in the cron directory
ADD crontab /etc/crontabs/root
# Give execution rights on the cron job
RUN chmod 0644 /etc/crontabs/root
# Create the log file to be able to run tail
RUN touch /var/log/cron.log
# Run the command on container startup using the JSON array syntax
CMD ["sh", "-c", "env > /var/log/cron.env && crond -f -d 8"]
</code>
<code># Use an official Alpine image as a parent image
FROM alpine:latest
# Install cron and any other dependencies you might need
RUN apk update &&
apk add dcron wget curl logrotate
# Add crontab file in the cron directory
ADD crontab /etc/crontabs/root
# Give execution rights on the cron job
RUN chmod 0644 /etc/crontabs/root
# Create the log file to be able to run tail
RUN touch /var/log/cron.log
# Run the command on container startup using the JSON array syntax
CMD ["sh", "-c", "env > /var/log/cron.env && crond -f -d 8"]
</code>
# Use an official Alpine image as a parent image
FROM alpine:latest
# Install cron and any other dependencies you might need
RUN apk update &&
apk add dcron wget curl logrotate
# Add crontab file in the cron directory
ADD crontab /etc/crontabs/root
# Give execution rights on the cron job
RUN chmod 0644 /etc/crontabs/root
# Create the log file to be able to run tail
RUN touch /var/log/cron.log
# Run the command on container startup using the JSON array syntax
CMD ["sh", "-c", "env > /var/log/cron.env && crond -f -d 8"]
Make a file called crontab and save it in the same folder as the dockerfile:
<code>* * * * * /bin/echo "Hello" >> /var/log/cron.log 2>&1
</code>
<code>* * * * * /bin/echo "Hello" >> /var/log/cron.log 2>&1
</code>
* * * * * /bin/echo "Hello" >> /var/log/cron.log 2>&1
Build the image with the command:
<code>docker build -t my-alpine-cron .
</code>
<code>docker build -t my-alpine-cron .
</code>
docker build -t my-alpine-cron .
Run the image and you should see the error message:
<code>2024-07-28 13:10:44 setpgid: Operation not permitted
</code>
<code>2024-07-28 13:10:44 setpgid: Operation not permitted
</code>
2024-07-28 13:10:44 setpgid: Operation not permitted
Why am I getting this error? What can I do to solve it?
OS Version/build: Windows 10 x64
App version: Docker Desktop 4.32.0