docker compatibility --platform doesn't work

[fugkco]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind bug

Description

Seems using the --platform tag via docker doesn't pull the expected image.

Steps to reproduce the issue:

1. Use podman to pull an arm64 image, and notice that it works fine:

   $ podman pull --platform linux/arm64 docker.io/node:12-buster-slim
   ...
   $ podman inspect docker.io/library/node:12-buster-slim --format '{{.Architecture}}'
   arm64
   $ docker inspect docker.io/library/node:12-buster-slim --format '{{.Architecture}}'
   arm64
   $ podman rmi node:12-buster-slim
   

2. Compare with to pulling with docker, which pulls the amd64:

   $ docker pull --platform linux/arm64 docker.io/node:12-buster-slim
   ...
   $ podman inspect docker.io/library/node:12-buster-slim --format '{{.Architecture}}'
   amd64
   $ docker inspect docker.io/library/node:12-buster-slim --format '{{.Architecture}}'
   amd64
   

Describe the results you received:
Pulled image is amd64

Describe the results you expected:
Expect docker pull to pull the platform requested, in above case arm64.

Additional information you deem important (e.g. issue happens only occasionally):

Output of podman version:

$ podman version
Version:      3.2.2
API Version:  3.2.2
Go Version:   go1.14.7
Built:        Thu Jan  1 01:00:00 1970
OS/Arch:      linux/amd64

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.21.0
  cgroupControllers: []
  cgroupManager: cgroupfs
  cgroupVersion: v1
  conmon:
    package: 'conmon: /usr/libexec/podman/conmon'
    path: /usr/libexec/podman/conmon
    version: 'conmon version 2.0.27, commit: '
  cpus: 8
  distribution:
    distribution: pop
    version: "21.04"
  eventLogger: journald
  hostname: pop-os
  idMappings:
    gidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
    uidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
  kernel: 5.11.0-7620-generic
  linkmode: dynamic
  memFree: 585052160
  memTotal: 16491663360
  ociRuntime:
    name: crun
    package: 'crun: /usr/bin/crun'
    path: /usr/bin/crun
    version: |-
      crun version 0.20.1.5-925d-dirty
      commit: 0d42f1109fd73548f44b01b3e84d04a279e99d2e
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
  os: linux
  remoteSocket:
    exists: true
    path: /run/user/1000/podman/podman.sock
  security:
    apparmorEnabled: false
    capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: true
    seccompEnabled: true
    seccompProfilePath: /usr/share/containers/seccomp.json
    selinuxEnabled: false
  serviceIsRemote: false
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: 'slirp4netns: /usr/bin/slirp4netns'
    version: |-
      slirp4netns version 1.1.8
      commit: unknown
      libslirp: 4.3.1-git
      SLIRP_CONFIG_VERSION_MAX: 3
      libseccomp: 2.4.3
  swapFree: 123064320
  swapTotal: 4294434816
  uptime: 233h 25m 3.35s (Approximately 9.71 days)
registries:
  search:
  - docker.io
  - quay.io
store:
  configFile: /home/fugkco/.config/containers/storage.conf
  containerStore:
    number: 9
    paused: 0
    running: 8
    stopped: 1
  graphDriverName: overlay
  graphOptions:
    overlay.mount_program:
      Executable: /usr/bin/fuse-overlayfs
      Package: 'fuse-overlayfs: /usr/bin/fuse-overlayfs'
      Version: |-
        fusermount3 version: 3.10.2
        fuse-overlayfs: version 1.5
        FUSE library version 3.10.2
        using FUSE kernel interface version 7.31
  graphRoot: /home/fugkco/.local/share/containers/storage
  graphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "false"
  imageStore:
    number: 27
  runRoot: /run/user/1000/containers
  volumePath: /home/fugkco/.local/share/containers/storage/volumes
version:
  APIVersion: 3.2.2
  Built: 0
  BuiltTime: Thu Jan  1 01:00:00 1970
  GitCommit: ""
  GoVersion: go1.14.7
  OsArch: linux/amd64
  Version: 3.2.2

Package info (e.g. output of rpm -q podman or apt list podman):

$ apt list podman
Listing... Done
podman/unknown,now 100:3.2.2-1 amd64 [installed]
podman/unknown 100:3.2.2-1 arm64
podman/unknown 100:3.2.2-1 armhf
podman/unknown 100:3.2.2-1 s390x

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide? (https://github.com/containers/podman/blob/master/troubleshooting.md)

Not checked with the latest version (not in a position to upgrade right now sadly), but had a look through the changelog and nothing springs out that would have addressed this.

Additional environment details (AWS, VirtualBox, physical, etc.):
Physical

[vrothberg]

Thanks for reaching out, @fugkco.

$ podman pull --platform linux/arm64 docker.io/node:12-buster-slim
...
$ podman inspect docker.io/library/node:12-buster-slim --format '{{.Architecture}}'
arm64

This looks correct to me.

Expect docker pull to pull the platform requested, in above case arm64.

Are you mixing docker and podman? It may be a lack of morning coffee but I do not understand the problem yet. Can you elaborate a bit more?

As far as I can see, Podman behaves correctly and pulls the arm64 image. I tested Docker 20.10.6 which is also pulling down the correct.

$ docker pull --platform linux/arm64 docker.io/node:12-buster-slim
...
$ podman inspect docker.io/library/node:12-buster-slim --format '{{.Architecture}}'
amd64
$ docker inspect docker.io/library/node:12-buster-slim --format '{{.Architecture}}'
amd64

You're using docker pull but podman inspect. Maybe that's the source of confusion?

[fugkco]

Hi @vrothberg,

Thanks for your time!

The issue is that when I point docker-client to podman.socket, and do a docker pull, podman doesn't pull the platform requested by docker client (it looks like it's ignoring it completely). When doing the same with podman directly, it works fine.

$ env | grep DOCKER_HOST
DOCKER_HOST=unix:///run/user/1000/podman/podman.sock
$ docker pull --platform linux/arm64 docker.io/node:12-buster-slim
...
$ docker inspect docker.io/library/node:12-buster-slim --format '{{.Architecture}}'
amd64

Here I am using docker client pointed to podman to pull the arm64 image of node:12-buster-slim, but when inspecting the image (whether via podman or docker), it is evident that podman pulled the amd64 despite the --platform arg explicitly asking for linux/arm64. On the other hand, using podman pull behaves correctly.

I put in the podman inspect commands in there for confirmation that the docker inspect command is indeed seeing the right architecture.

[vrothberg]

@fugkco, thanks for clarifying. I will have a look and provide a fix.

[vrothberg]

Opened #10979