Containers with Podman

Podman is a daemonless, rootless, container engine, which is designed to be a drop-in replacement for Docker. As a drop-in replacement for Docker, Podman supports the same commands and syntax.

Podman can support Docker Compose files if you install podman-compose. Some of the other advantages of using podman, is the ability to generate systemd service files or kubernetes Pod yaml from docker or docker-compose files.

Deploying a Container with Podman

To run a container

podman container run -d ngnix

-d or --detach means to run the contaier in the background.

Ports

Like Docker, if you need to access the container from a browser, you need to tell Podman what port the container will listen on. You use -p or --port The syntax is -p host:container.

for example if we want to access ngnix from 8080, we would add '-p 8080:80'

podman container run -d -p 8080:80 ngnix

Volumes

Use -v host-directory:container-directroy or --volume host-directory:container-directroy

If not instructed, podman will create a volume with a unique ID. You can point to a already created volume or host directory.

podman container run -d -v /srv/foo:/foo ngnix

You can also create a volume

podman volume create -name foo

have the container use the volume

podman container run -d -v foo:/foo ngnix

This will create a volume called foo. If created by a non-root user, it is stored in ~/.local/share/containers/storage, in /var/lib/container/storage if created by root. This can be changed in /etc/container/storage.conf or ~./config/container/storage.conf

You can add the volume with -v foo:/var

If you are deploying a rootless contaner on a system running SELinux, you need to add :z or :Z to the end of volumes. If the volume will be accessed by more than one container, use z. If the volume is only accessed by one container use Z. If you want to create a container tailored SELinux policy, look into udica.

Environment Variables

Enviromental variables are used to configure application settings within the container, like user name, passwords, ip of database.

Use --env or -e when invoking a enviromental variable.