Podman: A start point

In this post I will show how to install the Podman container tool on RHEL8 based systems.

According to the the definition at Podman official website ,

Podman is a utility provided as part of the libpod library. It can be used to create and maintain containers. The following tutorial will teach you how to set up Podman and perform some basic commands.

Basic concepts before start

We could some differences between architectures according to the following image.

Bare metal: Each app runs in a physical host with an Operating System, these apps need to share the same libraries and environment to run in the same host.
Virtualization: Each app runs in a virtual machine running. We can see an abstraction of physical hardware.
Containers: Containers are the abstraction at the app layers.

Why replace Docker with Podman?

Docker was considered the main tool to run containers for most years. This scenario has changed with the standardization of containers by OCI.

Podman permits you to run, build and deploy applications using Open Container Initiative (OCI)-compatible containers and container images.

We could consider some good points here to use Podman :

Daemonless: It does not require a daemon.
Rootless: It lets you run containers as a non-root user.
systemd: Podman runs containers with Systemd by default.
Kubernetes transition: Podman can generate YAML’s to move to Kubernetes.

Docker scenario: The Docker daemon may cause some problems in the environment like a single point of failure and the daemon own all child processes for the running containers.

Podman scenario: Podman interacts with Linux kernel to manage containers through the runC container runtime process instead of a daemon.

This following document explains why Redhat move from Docker to Podman:

https://www.redhat.com/en/blog/why-red-hat-investing-cri-o-and-podman

Environment

I am running my environment with RHEL8 OS with RedHat developer subscription and the following resource:

1 Libvirt vm with 4 Gbs RAM , 2 vcpus .

Create an account in the quay.io (image repository)

I recommend reading the following document about Developer and Smal Business Production subscriptions :

https://www.redhat.com/en/blog/new-year-new-red-hat-enterprise-linux-programs-easier-ways-access-rhel

This document can be use to RHEL8 based systems too!

Installation

Install the package


[root@podman01 ~]# dnf install podman

2. Check the podman version


[root@podman01 ~]# podman --version
podman version 2.0.5

3. Setup quay repository in /etc/containers/registries.conf file.


registries = ['registry.access.redhat.com', 'registry.redhat.io', 'docker.io' , 'quay.io']

4. Run command podman info


[root@podman01 ~]# sudo podman info

host:
  arch: amd64
  buildahVersion: 1.15.1
  cgroupVersion: v1
  conmon:
    package: conmon-2.0.20-2.module+el8.3.0+8221+97165c3f.x86_64
    path: /usr/bin/conmon
    version: 'conmon version 2.0.20, commit: 77ce9fd1e61ea89bd6cdc621b07446dd9e80e5b6'
  cpus: 2
  distribution:
    distribution: '"rhel"'
    version: "8.3"
  eventLogger: file
  hostname: podman01.example.com
  idMappings:
    gidmap: null
    uidmap: null
  kernel: 4.18.0-240.el8.x86_64
  linkmode: dynamic
  memFree: 2501382144
  memTotal: 3917524992
  ociRuntime:
    name: runc
    package: runc-1.0.0-68.rc92.module+el8.3.0+8221+97165c3f.x86_64
    path: /usr/bin/runc
    version: 'runc version spec: 1.0.2-dev'
  os: linux
  remoteSocket:
    path: /run/podman/podman.sock
  rootless: false
  slirp4netns:
    executable: ""
    package: ""
    version: ""
  swapFree: 2210394112
  swapTotal: 2210394112
  uptime: 49m 53.15s
registries:
  search:
  - registry.access.redhat.com
  - registry.redhat.io
  - docker.io
  - quay.io
store:
  configFile: /etc/containers/storage.conf
  containerStore:
    number: 0
    paused: 0
    running: 0
    stopped: 0
  graphDriverName: overlay
  graphOptions:
    overlay.mountopt: nodev,metacopy=on
  graphRoot: /var/lib/containers/storage
  graphStatus:
    Backing Filesystem: xfs
    Native Overlay Diff: "false"
    Supports d_type: "true"
    Using metacopy: "true"
  imageStore:
    number: 1
  runRoot: /var/run/containers/storage
  volumePath: /var/lib/containers/storage/volumes
version:
  APIVersion: 1
  Built: 1600877882
  BuiltTime: Wed Sep 23 13:18:02 2020
  GitCommit: ""
  GoVersion: go1.14.7
  OsArch: linux/amd64
  Version: 2.0.5

Podman basic operations

In this practice, I will create a WordPress site and following the main operations to practice.

Sign into quay.io


[root@podman01 ~]# podman login quay.io
Username: fajlinuxblog
Password:

Search images with CLI


[root@podman01 ~]# podman search apache

Let’s pull the wordpress image


[root@podman01 ~]#  podman pull quay.io/bitnami/nginx

Show the images


[root@podman01 ~]# podman images
REPOSITORY                                       TAG     IMAGE ID      CREATED       SIZE
quay.io/bitnami/nginx                            latest  91f438133f9c  19 hours ago  93.4 MB

Run a web container


[root@podman01 ~]# sudo podman run -d --name web1 -p 8082:80 quay.io/bitnami/nginx

Check the container proccess


[root@podman01 ~]# sudo podman ps

Execute bash to log into the container


[root@podman01 ~]# podman exec -it web1 /bin/bash 
bash-4.2$

Check the container logs


[root@podman01 ~]# podman logs web1
nginx 19:51:09.05 
nginx 19:51:09.05 Welcome to the Bitnami nginx container
nginx 19:51:09.05 Subscribe to project updates by watching https://github.com/bitnami/bitnami-docker-nginx
nginx 19:51:09.05 Submit issues and feature requests at https://github.com/bitnami/bitnami-docker-nginx/issues
nginx 19:51:09.05 
nginx 19:51:09.05 INFO  ==> ** Starting NGINX setup **
nginx 19:51:09.06 INFO  ==> Validating settings in NGINX_* env vars
nginx 19:51:09.07 INFO  ==> Initializing NGINX

nginx 19:51:09.07 INFO  ==> ** NGINX setup finished! **
nginx 19:51:09.08 INFO  ==> ** Starting NGINX **

Try the access of web server with http://<PODMAN HOST IP ADDRESS>:8082

I hope to write more about Podman and Kubernetes in the future!

That’s all folks!