Trying Podman as a Docker alternative

Podman as a Docker alternative

Before you begin

In this tutorial we’ll learn how to use Podman instead of Docker to manage containers. A Linux machine with Podman is required to follow this tutorial. These are some examples of how to install Podman (more information about its installation here):

# Install Podman Ubuntu 18.04
$ apt-get update
$ apt-get install software-properties-common -y
$ add-apt-repository -y ppa:projectatomic/ppa
$ apt-get install podman -y

# Install Podman Fedora 29/30
$ dnf install podman

Check installed version:

$ podman -v
podman version 1.6.2

$ podman version
Version:            1.6.2
RemoteAPI Version:  1
Go Version:         go1.11.13
OS/Arch:            linux/amd64

Podman CLI vs Docker CLI

Podman is known by its lightness, not having a daemon like Docker and by using the runC container runtime process. But apart from its lightweight architecture (fewer processes meaning more resources for our containers) we’ve prepared some commands in order to find out if Podman can make our life easier as container administrator.

Podman can connect to the same Docker registries like Docker CLI does to pull images. By default is trying Docker Hub as a default option as you can see in previous results. To log in to private remote repositories:

podman login <registry_url>
podman login docker.io # Docker Hub

Finally, podman login has the option --authfile allowing to pass a registry auth file as a parameter, useful for example to log in to GCR for example:

podman login --authfile my_secret_auth_file.json gcr.io

Podman ps

Start a couple of containers:

$ podman run -d nginx:alpine
$ podman run -d nginx:alpine

Check their status with a built-in watch:

$ podman ps -w n

# updating results every two seconds
$ podman ps -w 2

And finally sort the results:

$ podman ps --sort <title_name>
$ podman ps --sort created
CONTAINER ID  IMAGE                           COMMAND               CREATED        STATUS            PORTS  NAMES
08d139517070  docker.io/library/nginx:alpine  nginx -g daemon o...  2 seconds ago  Up 2 seconds ago         interesting_williams
cf8bed4b6d1a  docker.io/library/nginx:alpine  nginx -g daemon o...  7 minutes ago  Up 7 minutes ago         thirsty_chatelet

Podman logs

This command has a handy -l parameter allowing us to display the logs of the latest container deployed using Podman (without requiring a container name or ID):

podman logs -l
podman logs -l -f # follows log output

Podman stop

Podman command to stop last container:

$ podman stop -l
0189598647d3afef7c63b02d1e9e2980d478a7d0175ee50e2f74cb850b320aab

$ podman ps
CONTAINER ID  IMAGE                           COMMAND               CREATED            STATUS                PORTS  NAMES
1b2f56b56411  docker.io/library/redis:latest  redis-server          8 minutes ago      Up 6 minutes ago             unruffled_chaum
08d139517070  docker.io/library/nginx:alpine  nginx -g daemon o...  About an hour ago  Up About an hour ago         interesting_williams
cf8bed4b6d1a  docker.io/library/nginx:alpine  nginx -g daemon o...  2 hours ago        Up 2 hours ago               thirsty_chatelet

$ podman ps -a
CONTAINER ID  IMAGE                           COMMAND               CREATED            STATUS                    PORTS  NAMES
0189598647d3  docker.io/library/redis:latest  redis-server          6 minutes ago      Exited (0) 4 seconds ago         wizardly_dewdney
...

Podman command to stop all containers in one single command:

$ podman stop -a
0189598647d3afef7c63b02d1e9e2980d478a7d0175ee50e2f74cb850b320aab
1b2f56b56411510aebcc21191919c5fbd8047fe81bd984ae9a3540cadacdf998
08d139517070b1c3bd915e96855dca16ec155006d26e2a627b4f09b451021a0c
cf8bed4b6d1ae900fdd55c85a9de9a9344896e2377de850d271df2393a806a2d

$ podman ps -a
CONTAINER ID  IMAGE                           COMMAND               CREATED            STATUS                     PORTS  NAMES
0189598647d3  docker.io/library/redis:latest  redis-server          7 minutes ago      Exited (0) 32 seconds ago         wizardly_dewdney
1b2f56b56411  docker.io/library/redis:latest  redis-server          8 minutes ago      Exited (0) 2 seconds ago          unruffled_chaum
08d139517070  docker.io/library/nginx:alpine  nginx -g daemon o...  About an hour ago  Exited (0) 2 seconds ago          interesting_williams
cf8bed4b6d1a  docker.io/library/nginx:alpine  nginx -g daemon o...  2 hours ago        Exited (0) 2 seconds ago          thirsty_chatelet

Podman rm

Podman command to remove all containers in one single command (running and stopped containers included):

$ podman rm -a -f
0189598647d3afef7c63b02d1e9e2980d478a7d0175ee50e2f74cb850b320aab
1b2f56b56411510aebcc21191919c5fbd8047fe81bd984ae9a3540cadacdf998
08d139517070b1c3bd915e96855dca16ec155006d26e2a627b4f09b451021a0c
cf8bed4b6d1ae900fdd55c85a9de9a9344896e2377de850d271df2393a806a2d

.. and even their volumes:

$ podman rm -a -f -v

This is a very small portion of the capabilities that Podman can do but as a conclusion we can say that it can do almost the tasks that Docker CLI does plus some extra parameters and filtering.

Finally, you should definitely take a look at these books to fuel your Kubernetes knowledge: