Docker vs Podman

How does Docker work?

Docker

• Docker CLI asks the daemon to work with registries, images, containers and kernel.
• Here Docker Daemon provides all the functionality needed to:
  - push and pull images from a registry
  - ask the kernel to run containers
  - copy images to local container storage etc…
• Why using a Docker Daemon is not a great option?
  - a single point of failure
  - Daemon process owns all the child processes — i.e running containers
  - if the daemon fails then there will be orphaned processes
  - Docker containers are designed to be accessed as root users to execute commands that non-root users can’t execute
• Docker Local Repository: /var/lib/docker

How does Podman work?

Podman

• Podman directly interacts with image registry, container and image local storage and linux kernel (via runC container runtime process — not a daemon)
  - Podman is rootless and daemonless
  - Podman supports two modes of operation: rootful, in which case the container runs as root on the host system, and rootless, where the container runs under a standard Unix user account.
• Podman Local Repository (root) : /var/lib/containers (based on Open OCI (Open Container Initiative) standards)
• Podman Local Repository (rootless user) : ~/.local/share/containers (in user home directory)
• One of the Extra features in Podman that is not there in Docker:

podman generate kube <cont_ID>    //to generate kubernetes YAML file

Example:

[opc@control ~]$ podman generate kube 94afd17b052a

# Save the output of this file and use kubectl create -f to import
# it into Kubernetes.
#
# Created with podman-4.0.2
apiVersion: v1
kind: Pod
metadata:
 creationTimestamp: “2023–12–13T03:31:17Z”
 labels:
 app: new3pod
 name: new3_pod
spec:
 containers:
 — image: localhost/hello_from_puneeth:latest
 name: new3
 securityContext:
 capabilities:
 drop:
 — CAP_MKNOD
 — CAP_AUDIT_WRITE

• You can create pods using Podman:

podman pod create — name=test_pod

podman run -dt — pod test_pod quay.io/libpod/alpine_nginx

podman ps — pod

podman pod list