RHCSA Practical Lab Series – Building a Container Image with Podman

🔍 Lab 13: Creating a Custom Container Image

📌 Objective

In this lab, you will:

✔ Install Podman and required container tools
✔ Download a Containerfile and build a container image
✔ Ensure the image is named appserver
✔ Verify the created image

📌 Step 1: Install Container Management Tools

🔹 Ensure container-tools is installed:

[root@node1 ~]# dnf -y install container-tools

📌 Explanation:

• Installs Podman and other required tools for container management.
• The -y flag automatically confirms installation.

✅ Once installed, proceed to Step 2.

📌 Step 2: Switch to devops User

🔹 Log in as devops to manage containers:

[root@node1 ~]# ssh devops@node1

📌 Why? Running containers as a non-root user improves security in production environments.

✅ If successfully logged in, the prompt should change to [devops@node1 ~]$.

📌 Step 3: Authenticate with the Container Registry

🔹 Log in to the container registry to pull and push images:

[devops@node1 ~]$ podman login -u admin -p SecurePass123 registry.cloudnetops.tech

📌 Explanation:

• podman login → Authenticates with a container registry.
• -u admin → Uses admin as the username.
• -p SecurePass123 → Password for authentication.
• registry.cloudnetops.tech → The container registry URL.

✅ If login is successful, proceed to Step 4.

📌 Step 4: Download the Containerfile

🔹 Retrieve the Containerfile from the remote server:

[devops@node1 ~]$ wget http://classroom/Containerfile

📌 Explanation:

• wget → Downloads files from a remote server.
• http://classroom/Containerfile → The URL hosting the Containerfile.

✅ Once downloaded, you should see a file named Containerfile in the current directory.

📌 Step 5: Build the Container Image

🔹 Use Podman to build the image and tag it as appserver:

[devops@node1 ~]$ podman build -t appserver .

📌 Explanation:

• podman build → Builds a container image from a Containerfile.
• -t appserver → Tags the image as appserver.
• . → Uses the current directory as the build context.

✅ If the build succeeds, the image is now stored locally.

📌 Step 6: Verify the Built Image

🔹 List available images to confirm the build:

[devops@node1 ~]$ podman images

📌 Expected Output:

REPOSITORY                           TAG      IMAGE ID       CREATED         SIZE
localhost/appserver                  latest   3f4b1e2c1a56   2 minutes ago   125MB

✅ If appserver appears in the list, the image was built successfully.

🔹 Inspect the image details:

[devops@node1 ~]$ podman inspect appserver

📌 Step 7: Run and Test the Container (Optional)

🔹 Run the newly built container to test its functionality:

[devops@node1 ~]$ podman run -d --name test_app -p 8080:80 appserver

📌 Explanation:

• -d → Runs the container in detached mode.
• --name test_app → Assigns a name to the running container.
• -p 8080:80 → Maps port 8080 on the host to port 80 in the container.
• appserver → Uses the newly built image.

🔹 Check if the container is running:

[devops@node1 ~]$ podman ps

📌 Expected Output:

CONTAINER ID  IMAGE       COMMAND  CREATED        STATUS        PORTS       NAMES
a1b2c3d4e5f6  appserver   ...      10 seconds ago  Up 5 seconds  8080->80/tcp test_app

✅ If the container is running, it was successfully deployed!

✅ Final Summary

✔ Installed Podman and container tools
✔ Logged in as a non-root user (devops)
✔ Pulled a Containerfile and built an image (appserver)
✔ Verified the image and tested container execution

📌 Next Lab: Running a Container as a Systemd Service

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