Red Hat OpenShift Development I: Introduction to Containers with Podman

Instructions

1. Create a new container with the following parameters:

   • Container name: nginx

   • Container image: registry.ocp4.example.com:8443/redhattraining/podman-nginx-helloworld

   Route traffic from port 8080 on your machine to port 8080 inside of the container. Use the -d option to run the container in the background.

   [student@workstation ~]$ podman run --name nginx -d -p 8080:8080 \
     registry.ocp4.example.com:8443/redhattraining/podman-nginx-helloworld
   Trying to pull registry.ocp4.example.com:8443/redhattraining/podman-nginx-helloworld:latest...
   ...output omitted...
   3c2b...fa84

2. In a web browser, navigate to localhost:8080. You are presented with a 404 Not Found error page.

3. Troubleshoot the issue.

   1. Use the podman cp command to copy the /var/log/nginx/error.log log file in the nginx container to your local machine.

      In your terminal, execute the following command:

      [student@workstation ~]$ podman cp nginx:/var/log/nginx/error.log error.log
      no output expected

   2. View the contents of the log file.

      [student@workstation ~]$ gedit error.log
      2022/04/26 12:19:17 [error] 2#0: *2 "/usr/share/nginx/html/public/index.html" is not found (2: No such file or directory), client: 10.0.2.100, server: _, request: "GET / HTTP/1.1", host: "localhost:8080"
      2022/04/26 12:19:17 [error] 2#0: *2 open() "/usr/share/nginx/html/public/404.html" failed (2: No such file or directory), client: 10.0.2.100, server: _, request: "GET / HTTP/1.1", host: "localhost:8080"

      The server cannot read the /usr/share/nginx/html/public/index.html file.

   3. Verify the contents of the /usr/share/nginx/html/public directory.

      [student@workstation ~]$ podman exec nginx ls /usr/share/nginx/html/public
      ls: cannot access '/usr/share/nginx/html/public': No such file or directory

      The directory does not exist in the container.

   4. Verify the contents of the /usr/share/nginx/html directory.

      [student@workstation ~]$ podman exec nginx ls /usr/share/nginx/html
      404.html
      50x.html
      index.html
      nginx-logo.png
      poweredby.png

      The index.html page exists in the /usr/share/nginx/html directory.

4. Correct the server configuration.

   1. Copy the /etc/nginx/nginx.conf file from the container to your machine.

      [student@workstation ~]$ podman cp nginx:/etc/nginx/nginx.conf .
      no output expected

   2. Open the nginx.conf file in a text editor, such as VSCodium or Gedit.

      In the server directive, change the root parameter to the /usr/share/nginx/html/ value.

      [student@workstation ~]$ gedit nginx.conf
      ...file omitted...
          server {
              listen       8080 default_server;
              server_name  _;
              root         /usr/share/nginx/html/;
      ...file omitted...

      Save the change in the nginx.conf file.

   3. Replace the /etc/nginx/nginx.conf file in the container with the modified nginx.conf file.

      [student@workstation ~]$ podman cp nginx.conf nginx:/etc/nginx
      no output expected

      Note

      You can also use the podman exec command with the --interactive and --tty options to open an interactive shell to modify files directly in a running container. For example, you can use the podman exec -ti nginx vim /etc/nginx/nginx.conf command to interactively modify the nginx.conf file with the vim text editor.

      Keep in mind that changes applied to a running container are temporary and do not persist if you delete the container. For persistent changes, you must rebuild the container image. Rebuilding container images is covered elsewhere in this course.

5. Verify the functionality of the running container.

   1. Reload the server configuration.

      [student@workstation ~]$ podman exec nginx nginx -s reload
      no output expected

   2. In a web browser, navigate to localhost:8080. You are presented with the index.html page contents.