Accept --entrypoint=["some","argument"] for create/run command

[Romain-Geissler-1A]

Description

Hi,

It seems for now --entrypoint=argument can only specify a single argument string. It would be cool if we were able to specify a multiple arguments json array, like in a Dockerfile. Podman already supports this json array syntax.

Reproduce

> docker run -t -i --rm --entrypoint='["python3","--version"]'  quay.io/fedora/fedora
docker: Error response from daemon: failed to create task for container: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: exec: "[\"python3\",\"--version\"]": executable file not found in $PATH: unknown.

Expected behavior

It works fine (ie runs python3 --version like it does with podman:

> podman run -t -i --rm --entrypoint='["python3","--version"]'  quay.io/fedora/fedora
Python 3.12.0

docker version

Client:
 Version:           25.0.2
 API version:       1.43 (downgraded from 1.44)
 Go version:        go1.21.6
 Git commit:        29cf629
 Built:             Thu Feb  1 00:22:06 2024
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          24.0.6
  API version:      1.43 (minimum version 1.12)
  Go version:       go1.20.7
  Git commit:       1a79695
  Built:            Mon Sep  4 12:31:49 2023
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.6.24
  GitCommit:        61f9fd88f79f081d64d6fa3bb1a0dc71ec870523
 runc:
  Version:          1.1.9
  GitCommit:        v1.1.9-0-gccaecfc
 docker-init:       
  Version:          0.19.0
  GitCommit:        de40ad0

docker info

Client:
 Version:    25.0.2
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.12.1
    Path:     /usr/libexec/docker/cli-plugins/docker-buildx

Server:
 Containers: 9
  Running: 6
  Paused: 0
  Stopped: 3
 Images: 80
 Server Version: 24.0.6
 Storage Driver: overlay2
  Backing Filesystem: xfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 61f9fd88f79f081d64d6fa3bb1a0dc71ec870523
 runc version: v1.1.9-0-gccaecfc
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 5.14.0-362.8.1.el9_3.x86_64
 Operating System: Red Hat Enterprise Linux 9.3 (Plow)
 OSType: linux
 Architecture: x86_64
 CPUs: 12
 Total Memory: 31.05GiB
 Name: nceswbbaprd1320.rnd.amadeus.net
 ID: 2cdf1796-faae-40cd-8ece-afacd1c5b2d9
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false
 Default Address Pools:
   Base: 10.225.0.0/16, Size: 24

Additional Info

No response

[cpuguy83]

What is the use case for this?
You can do docker run --entrypoint python3 quay.io/fedora/fedora --version
I'm not quite sure why people really use --entrypoint at all except to overwrite what's in the image.

[Romain-Geissler-1A]

The image may define both an ENTRYPOINT and CMD and in this case you might want to override just the entrypoint while keeping the default CMD. This custom entry point can be some wrapper binary which takes multiple parameter (as ENTRYPOINT in a dockerfile might accept multiple parameters).

[fheinecke]

What is the use case for this?

There are some poorly designed services with features (such as Github Actions job services) that can take an --entrypoint arg, but don't provide any other way to potentially specify container command or args. This would be a nice workaround, under the assumption that third parties won't fix their software.