How to Quickly Set Up a Podman Environment on CentOS 8

Install Podman

On a CentOS 8 host, install the Podman container runtime: # yum -y install podman Adjust the user namespace limit to allow enough namespaces:

# echo "user.max_user_namespaces=28633" >> /etc/sysctl.d/userns.conf
# sysctl -p /etc/sysctl.d/userns.conf
# user.max_user_namespaces = 28633

Run a Test Container

Verify Podman works by pulling and inspecting the Red Hat UBI image: # podman run ubi8/ubi cat /etc/os-release The command outputs the OS details of the UBI image, confirming the pull succeeded.

Create a Dockerfile

Prepare a directory for the Dockerfile and build a custom image that includes the nano editor:

# mkdir ~/myc
# cd ~/myc
# vim Dockerfile
FROM ubi8/ubi:latest
RUN dnf install -y nano

Build the Custom Image

Build the image and tag it ubi-with-nano:

# podman build -f Dockerfile -t ubi-with-nano
STEP 1/2: FROM ubi8/ubi:latest
STEP 2/2: RUN dnf install -y nano
... (build output)

List images to confirm the new image exists:

# podman images

Run the New Image

Check that nano is available inside the container:

# podman run localhost/ubi-with-nano /usr/bin/which nano
/usr/bin/nano

Start an interactive shell:

# podman run -it localhost/ubi-with-nano /bin/bash
[root@container /]# ls
... (list of directories)

Exit the container with exit.

Manage Containers

List running containers: # podman ps List all containers, including stopped ones:

# podman ps -a

Persist Data with a Bind Mount

Create a host directory to store persistent data: # mkdir /pod_data Run a container binding /pod_data on the host to /storage inside the container (SELinux context :Z):

# podman run -it --volume /pod_data:/storage:Z localhost/ubi-with-nano
[root@container /]# echo "hello podman" >> /storage/msg.txt
[root@container /]# exit
# cat /pod_data/msg.txt
hello podman

The file written inside the container persists on the host after the container stops.