shared memory between containers in pod not working

[PinkJohnOfUs]

/kind bug

Description

Pod uses same IPC namespace, but it is not possible to use /dev/shm

Steps to reproduce the issue:

1. create Pod

podman pod create --name shm-pod

2. run sender and receiver container

podman run --name rx-shm -dt --pod shm-pod alpine
podman run --name tx-shm -dt --pod shm-pod alpine

3. send data over /dev/shm

podman exec -it tx-shm /bin/sh
# echo "blub" > /dev/shm/test

4. try receiving data over /dev/shm

podman exec -it rx-shm /bin/sh
# cat  /dev/shm/test

Describe the results you received:

cat: can't open '/dev/shm/test': No such file or directory

Describe the results you expected:

blub

output of podman pod inspect shm-pod

podman pod inspect shm-pod
{
    "Id": "7356e64626761ae9edab93677508f509c5eba6a234dc2786f1a3f77a4b3b451c",
    "Name": "shm-pod",
    "Created": "2020-10-29T12:24:36.872670983+01:00",
    "CreateCommand": [
        "podman",
        "pod",
        "create",
        "--name",
        "shm-pod"
    ],
    "State": "Running",
    "Hostname": "shm-pod",
    "CreateCgroup": true,
    "CgroupParent": "/libpod_parent",
    "CgroupPath": "/libpod_parent/7356e64626761ae9edab93677508f509c5eba6a234dc2786f1a3f77a4b3b451c",
    "CreateInfra": true,
    "InfraContainerID": "67ebfdee5ac797f63c792a59d9fb3e71cdb8ace0ba03dd5f08209d4848a9e744",
    "InfraConfig": {
        "PortBindings": {},
        "HostNetwork": false,
        "StaticIP": "",
        "StaticMAC": null,
        "NoManageResolvConf": false,
        "DNSServer": null,
        "DNSSearch": null,
        "DNSOption": null,
        "NoManageHosts": false,
        "HostAdd": null,
        "Networks": null
    },
    "SharedNamespaces": [
        "uts",
        "ipc",
        "net"
    ],
    "NumContainers": 3,
    "Containers": [
        {
            "Id": "67ebfdee5ac797f63c792a59d9fb3e71cdb8ace0ba03dd5f08209d4848a9e744",
            "Name": "7356e6462676-infra",
            "State": "running"
        },
        {
            "Id": "76cbe93efd3fae5186ecf5a7a2f2c85426bc8d9cabeb5c333416a179edf2566a",
            "Name": "tx-shm",
            "State": "running"
        },
        {
            "Id": "9d92be4a220664273abb660448ca01b20e299131e46b8c3db386dc7538488d94",
            "Name": "rx-shm",
            "State": "running"
        }
    ]
}

Output of podman version:

Version:      2.1.1
API Version:  2.0.0
Go Version:   go1.15.2
Built:        Thu Jan  1 01:00:00 1970
OS/Arch:      linux/amd64

Output of podman info --debug:

host:
  arch: amd64
  buildahVersion: 1.16.1
  cgroupManager: cgroupfs
  cgroupVersion: v1
  conmon:
    package: 'conmon: /usr/libexec/podman/conmon'
    path: /usr/libexec/podman/conmon
    version: 'conmon version 2.0.20, commit: '
  cpus: 12
  distribution:
    distribution: ubuntu
    version: "18.04"
  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: 5.4.0-52-generic
  linkmode: dynamic
  memFree: 5172588544
  memTotal: 33075073024
  ociRuntime:
    name: runc
    package: 'containerd.io: /usr/bin/runc'
    path: /usr/bin/runc
    version: |-
      runc version 1.0.0-rc10
      commit: dc9208a3303feef5b3839f4323d9beb36df0a9dd
      spec: 1.0.1-dev
  os: linux
  remoteSocket:
    exists: true
    path: /run/user/1000/podman/podman.sock
  rootless: true
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: 'slirp4netns: /usr/bin/slirp4netns'
    version: |-
      slirp4netns version 1.1.4
      commit: unknown
      libslirp: 4.3.1-git
      SLIRP_CONFIG_VERSION_MAX: 3
  swapFree: 4293386240
  swapTotal: 4294434816
  uptime: 28h 50m 17.65s (Approximately 1.17 days)
registries:
  search:
  - docker.io
  - quay.io
store:
  configFile: /home/kiki/.config/containers/storage.conf
  containerStore:
    number: 12
    paused: 0
    running: 3
    stopped: 9
  graphDriverName: vfs
  graphOptions: {}
  graphRoot: /home/kiki/.local/share/containers/storage
  graphStatus: {}
  imageStore:
    number: 35
  runRoot: /run/user/1000/containers
  volumePath: /home/kiki/.local/share/containers/storage/volumes
version:
  APIVersion: 2.0.0
  Built: 0
  BuiltTime: Thu Jan  1 01:00:00 1970
  GitCommit: ""
  GoVersion: go1.15.2
  OsArch: linux/amd64
  Version: 2.1.1

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

Listing... Done
podman/unknown,now 2.1.1~2 amd64 [installed]

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide?

Yes

tested on physical device

[albertxos]

@rhatdan thank you for your great podman4soafee presentation today.
Looking forward to see podman in action.
Is there a way to make your own infra-container implementation?
^^that was my first podman issue ;)

[rhatdan]

Yes you can by modifying containers.conf

 grep infra /usr/share/containers/containers.conf 
# Default command to run the infra container
#infra_command = "/pause"
# Infra (pause) container image name for pod infra containers.  When running a
#infra_image = ""

But I am not sure what you are attempting to do. You might want to look into --init-ctr instead of changing infra image.