Allow --entrypoint to be set to null in a docker run or docker create

[programmerq]

I would like to be able to "unset" an ENTRYPOINT at the command line when creating a container.

Using this Dockerfile and entrypoint.sh as an example:

Dockerfile:

FROM alpine
ADD entrypoint.sh /entrypoint.sh
RUN chmod 755 /entrypoint.sh
ENTRYPOINT ["/entrypoint.sh"]
CMD echo foobar

entrypoint:

#!/bin/sh
echo "I am an entrypoint"
exec "$@"

If I wanted to unset the entrypoint, I would like to be able to run this: docker run --entrypoint='' --rm -it image echo foo

I would expect this to produce the following output:

foo

but it does the following instead:

I am an entrypoint
foo

Providing some way for docker run or docker create to force the ENTRYPOINT to be null without having to create another image would be great.

[mountkin]

Try this
docker run --entrypoint=/bin/echo --rm image foo

[programmerq]

I'm aware that this and other workarounds exist, but that doesn't mean that
this issue couldn't or shouldn't be addressed.
On Jun 13, 2016 5:11 PM, "Shijiang Wei" notifications@github.com wrote:

Try this
docker run --entrypoint=/bin/echo --rm image foo

—
You are receiving this because you authored the thread.
Reply to this email directly, view it on GitHub
#23498 (comment),
or mute the thread
https://github.com/notifications/unsubscribe/AACRnuHYnJydqWbZbVezdavvgV-VZHXkks5qLeOIgaJpZM4I0tri
.

[yongtang]

@programmerq I created a pull request #23718 to address this issue. If --entrypoint= (with empty string "") is passed then docker run or docker create will unset the entrypoint and rely on the default behavior.

Please let me know if there are any issues.

[marcodelapierre]

As regards the entrypoint... should we just ensure that it's unset, and then do everything through the run argument? At this point :

$ podman run -it --rm --entrypoint '' --env-file /home/ubuntu/singularity-hpc/modules/python/3.9.2-slim/99-shpc.sh -v /data docker.io/library/python:3.9.2-slim echo ciao
ciao

The main drawback is that there's no choice over which shell is used

Will keep looking for other ways

[thaJeztah]

most images only have a CMD set, no separate ENTRYPOINT, so you won't have to override it, but you can docker inspect the image to know what it has configured;

docker inspect --format '{{json .Config}}' docker.io/library/python:3.9.2-slim | jq .
{
  "Hostname": "",
  "Domainname": "",
  "User": "",
  "AttachStdin": false,
  "AttachStdout": false,
  "AttachStderr": false,
  "Tty": false,
  "OpenStdin": false,
  "StdinOnce": false,
  "Env": [
    "PATH=/usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
    "LANG=C.UTF-8",
    "GPG_KEY=E3FF2839C048B25C084DEBE9B26995E310250568",
    "PYTHON_VERSION=3.9.2",
    "PYTHON_PIP_VERSION=21.0.1",
    "PYTHON_GET_PIP_URL=https://github.com/pypa/get-pip/raw/b60e2320d9e8d02348525bd74e871e466afdf77c/get-pip.py",
    "PYTHON_GET_PIP_SHA256=c3b81e5d06371e135fb3156dc7d8fd6270735088428c4a9a5ec1f342e2024565"
  ],
  "Cmd": [
    "python3"
  ],
  "Image": "sha256:09147162b3f325a1bdc0df946f3ac8ed04e7690c7d17a754f88fc640cd1a23d4",
  "Volumes": null,
  "WorkingDir": "",
  "Entrypoint": null,
  "OnBuild": null,
  "Labels": null
}