Chapter 7. Working with pods

Containers are the smallest unit that you can manage with Podman, Skopeo and Buildah container tools. A Podman pod is a group of one or more containers. The Pod concept was introduced by Kubernetes. Podman pods are similar to the Kubernetes definition. Pods are the smallest compute units that you can create, deploy, and manage in OpenShift or Kubernetes environments. Every Podman pod includes an infra container. This container holds the namespaces associated with the pod and allows Podman to connect other containers to the pod. It allows you to start and stop containers within the pod and the pod will stay running. The default infra container on the registry.access.redhat.com/ubi8/pause image.

7.1. Creating pods

This procedure shows how to create a pod with one container.

Prerequisites

  • The Podman tool is installed.

    #  yum module install -y container-tools

Procedure

  1. Create an empty pod:

    $ podman pod create --name mypod
    223df6b390b4ea87a090a4b5207f7b9b003187a6960bd37631ae9bc12c433aff
    The pod is in the initial state Created.

    The pod is in the initial state Created.

  2. Optional: List all pods:

    $ podman pod ps
    POD ID         NAME    STATUS    CREATED                  # OF CONTAINERS   INFRA ID
    223df6b390b4   mypod   Created   Less than a second ago   1                 3afdcd93de3e

    Notice that the pod has one container in it.

  3. Optional: List all pods and containers associated with them:

    $ podman ps -a --pod
    CONTAINER ID  IMAGE                 COMMAND  CREATED                 STATUS   PORTS  NAMES               POD
    3afdcd93de3e  registry.access.redhat.com/ubi8/pause            Less than a second ago  Created         223df6b390b4-infra  223df6b390b4

    You can see that the pod ID from podman ps command matches the pod ID in the podman pod ps command. The default infra container is based on the registry.access.redhat.com/ubi8/pause image.

  4. Run a container named myubi in the existing pod named mypod:

    $ podman run -dt --name myubi --pod mypod registry.access.redhat.com/ubi8/ubi  /bin/bash
    5df5c48fea87860cf75822ceab8370548b04c78be9fc156570949013863ccf71
  5. Optional: List all pods:

    $ podman pod ps
    POD ID         NAME    STATUS    CREATED                  # OF CONTAINERS   INFRA ID
    223df6b390b4   mypod   Running   Less than a second ago   2                 3afdcd93de3e

    You can see that the pod has two containers in it.

  6. Optional: List all pods and containers associated with them:

    $ podman ps -a --pod
    CONTAINER ID  IMAGE                                       COMMAND    CREATED                 STATUS                     PORTS  NAMES               POD
    5df5c48fea87  registry.access.redhat.com/ubi8/ubi:latest  /bin/bash  Less than a second ago  Up Less than a second ago         myubi               223df6b390b4
    3afdcd93de3e  registry.access.redhat.com/ubi8/pause                                   Less than a second ago  Up Less than a second ago         223df6b390b4-infra  223df6b390b4

Additional resources

7.2. Displaying pod information

This procedure provides information on how to display pod information.

Prerequisites

  • The Podman tool is installed.

    #  yum module install -y container-tools
  • The pod has been created. For details, see section Creating pods.

Procedure

  • Display active processes running in a pod:

    • To display the running processes of containers in a pod, enter:

      $ podman pod top mypod
      USER   PID   PPID   %CPU    ELAPSED         TTY     TIME   COMMAND
      0      1     0      0.000   24.077433518s   ?       0s     /pause
      root   1     0      0.000   24.078146025s   pts/0   0s     /bin/bash
    • To display a live stream of resource usage stats for containers in one or more pods, enter:

      $ podman pod stats -a --no-stream
      ID             NAME              CPU %   MEM USAGE / LIMIT   MEM %   NET IO    BLOCK IO   PIDS
      a9f807ffaacd   frosty_hodgkin    --      3.092MB / 16.7GB    0.02%   -- / --   -- / --    2
      3b33001239ee   sleepy_stallman   --      -- / --             --      -- / --   -- / --    --
    • To display information describing the pod, enter:

      $ podman pod inspect mypod
      {
         "Id": "db99446fa9c6d10b973d1ce55a42a6850357e0cd447d9bac5627bb2516b5b19a",
         "Name": "mypod",
         "Created": "2020-09-08T10:35:07.536541534+02:00",
         "CreateCommand": [
             "podman",
             "pod",
             "create",
             "--name",
             "mypod"
         ],
         "State": "Running",
         "Hostname": "mypod",
         "CreateCgroup": false,
         "CgroupParent": "/libpod_parent",
         "CgroupPath": "/libpod_parent/db99446fa9c6d10b973d1ce55a42a6850357e0cd447d9bac5627bb2516b5b19a",
         "CreateInfra": false,
         "InfraContainerID": "891c54f70783dcad596d888040700d93f3ead01921894bc19c10b0a03c738ff7",
         "SharedNamespaces": [
             "uts",
             "ipc",
             "net"
         ],
         "NumContainers": 2,
         "Containers": [
             {
                 "Id": "891c54f70783dcad596d888040700d93f3ead01921894bc19c10b0a03c738ff7",
                 "Name": "db99446fa9c6-infra",
                 "State": "running"
             },
             {
                 "Id": "effc5bbcfe505b522e3bf8fbb5705a39f94a455a66fd81e542bcc27d39727d2d",
                 "Name": "myubi",
                 "State": "running"
             }
         ]
      }

      You can see information about containers in the pod.

Additional resources

  • podman pod top man page
  • podman-pod-stats man page
  • podman-pod-inspect man page

7.3. Stopping pods

You can stop one or more pods using the podman pod stop command.

Prerequisites

  • The Podman tool is installed.

    #  yum module install -y container-tools
  • The pod has been created. For details, see section Creating pods.

Procedure

  1. Stop the pod mypod:

    $ podman pod stop mypod
  2. Optional: List all pods and containers associated with them:

    $ podman ps -a --pod
    CONTAINER ID  IMAGE                               COMMAND    CREATED             STATUS                    PORTS   NAMES               POD ID        PODNAME
    5df5c48fea87  registry.redhat.io/ubi8/ubi:latest  /bin/bash  About a minute ago  Exited (0) 7 seconds ago          myubi               223df6b390b4  mypod
    
    3afdcd93de3e  registry.access.redhat.com/ubi8/pause                           About a minute ago  Exited (0) 7 seconds ago          8a4e6527ac9d-infra  223df6b390b4  mypod

    You can see that the pod mypod and container myubi are in "Exited" status.

Additional resources

  • podman-pod-stop man page

7.4. Removing pods

You can remove one or more stopped pods and containers using the podman pod rm command.

Prerequisites

  • The Podman tool is installed.

    #  yum module install -y container-tools
  • The pod has been created. For details, see section Creating pods.
  • The pod has been stopped. For details, see section Stopping pods.

Procedure

  1. Remove the pod mypod, type:

    $ podman pod rm mypod
    223df6b390b4ea87a090a4b5207f7b9b003187a6960bd37631ae9bc12c433aff

    Note that removing the pod automatically removes all containers inside it.

  2. Optional: Check that all containers and pods were removed:

    $ podman ps
    $ podman pod ps

Additional resources

  • podman-pod-rm man page