EntryPoint¶

https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#entrypoint

example¶

docker-entrypoint.sh

#!/bin/bash
set -e
exec "$@"

docker entrypoint

COPY ./docker-entrypoint.sh /
ENTRYPOINT ["/docker-entrypoint.sh"]
CMD ["/bin/bash"]

change the docker-entrypoint file to update .condarc channel_alias¶

docker-entrypoint.sh

#!/bin/bash
set -e
# Update channel_alias setting in .condarc
if [ -n "$CONDA_CHANNEL_ALIAS" ]; then
    conda config --set channel_alias "$CONDA_CHANNEL_ALIAS"
fi
exec "$@"

cmd vs entrypoint¶

The main difference between CMD and ENTRYPOINT in a Dockerfile lies in how they are used and overridden when running a container.

CMD¶

• The CMD instruction in a Dockerfile specifies the default command to run when the container starts.

• If a Dockerfile has multiple CMD instructions, only the last one will take effect.

• The CMD instruction can be overridden when running the container by specifying a command at the end of the docker run command. If no command is specified, the CMD instruction from the Dockerfile is executed.

• If the Dockerfile specifies an ENTRYPOINT, the CMD values are appended to the ENTRYPOINT to form the command that is run.

Example:

CMD ["nginx", "-g", "daemon off;"]

ENTRYPOINT¶

• The ENTRYPOINT instruction in a Dockerfile specifies the executable that will run when the container starts.

• If a Dockerfile has multiple ENTRYPOINT instructions, only the last one will take effect.

• The ENTRYPOINT instruction cannot be overridden like CMD. Instead, any commands provided when running the container are passed as arguments to the ENTRYPOINT.

• If the Dockerfile specifies both ENTRYPOINT and CMD, the CMD values are passed as arguments to the ENTRYPOINT.

Example:

ENTRYPOINT ["nginx", "-g", "daemon off;"]

In summary, ENTRYPOINT sets the main command and CMD provides default arguments for that command. When both are used together, CMD values are passed as arguments to ENTRYPOINT.