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Podman : A Basic Example of Using Podman With Dockerfiles (Oracle Database and ORDS) on Oracle Linux 8 (OL8)

This articles shows how to use Podman with existing Dockerfiles as a replacement for Docker. It is not meant as a best practice for how to use Podman, but a simple example for people with existing Docker experience.

Related articles.

My Setup

This article described how to install Podman on Oracle Linux 8 (OL8).

I'm doing this installation on my Vagrant build for Podman (here). These are the important locations on the VM.

# The base location for the Git repositories.
BASE_DIR=/u01

# The directory where all the software is sitting on host.
SOFTWARE_DIR=/vagrant/software

If you are running this example from the Vagrant build, the Docker Hub repository (docker.io) is already enabled. There is also a user called "container_user" set up, which can run the podman command without the need for "sudo". The commands in this article assume you have a similar setup. If not, simply add "sudo " to the start of each command.

We need a location to use for persistent storage, so we create the following directories and change their ownership so the container can read/write to them.

mkdir -p /u01/volumes/ol8_19_ords_tomcat
mkdir -p /u01/volumes/ol8_19_ords_db

# As root.
groupadd -g 1042 container_fg
chown -R :container_fg /u01
chmod -R 775 /u01/volumes
chmod -R g+s /u01/volumes
usermod -aG container_fg container_user

Clone the Git Repository

Clone my Dockerfiles repository. We are going to use them without any amendments.

cd ${BASE_DIR}
git clone https://github.com/oraclebase/dockerfiles.git

Make Docker Hub Available

If you are used to using Docker and want to make Docker Hub images available, make the following change in the "/etc/containers/registries.conf" file.

# From:
[registries.search]
registries = ['container-registry.oracle.com', 'registry.access.redhat.com', 'registry.redhat.io']

# To:
[registries.search]
registries = ['container-registry.oracle.com', 'docker.io', 'registry.access.redhat.com', 'registry.redhat.io']

Pull Oracle Linux 8 Image

Pull the latest "oraclelinux:8" image from Docker Hub.

podman pull oraclelinux:8-slim

Build the Database Image

We switch to the "software" directory for the database build, copy the software into place, switch back to the main directory and perform the build.

cd ${BASE_DIR}/dockerfiles/database/ol8_19/software

cp ${SOFTWARE_DIR}/LINUX.X64_193000_db_home.zip .
cp ${SOFTWARE_DIR}/apex_20.1_en.zip .

cd ${BASE_DIR}/dockerfiles/database/ol8_19

podman build --format docker --no-cache -t ol8_19:latest .

Build the ORDS Image

We switch to the "software" directory for the ORDS build, copy the software into place, switch back to the main directory and perform the build.

cd ${BASE_DIR}/dockerfiles/ords/ol8_ords/software

cp ${SOFTWARE_DIR}/apex_20.1_en.zip .
cp ${SOFTWARE_DIR}/apache-tomcat-9.0.34.tar.gz .
cp ${SOFTWARE_DIR}/ords-19.4.0.352.1226.zip .
cp ${SOFTWARE_DIR}/sqlcl-19.4.0.354.0937.zip .
cp ${SOFTWARE_DIR}/OpenJDK11U-jdk_x64_linux_hotspot_11.0.7_10.tar.gz .

cd ${BASE_DIR}/dockerfiles/ords/ol8_ords

podman build --format docker --no-cache -t ol8_ords:latest .

Create a Pod

A pod houses zero to many containers. All containers in the pod can automatically talk to each other on the ports exposed by the containers, so we don't have to worry about any explicit networking. We do have to decide which ports we want to expose to the host server.

Create a new Pod called "my_pod" and make sure the correct ports are exposed. Multiple ports can be created as comma-separated list using the "-p" or "--publish" flag. In the example below we've explicitly listed the "host:container" relationship for each port.

podman pod create --name my_pod --publish=1521:1521,5500:5500,8080:8080,8443:8443

We can see information about the pod using the "ls" and "inspect" commands.

podman pod ls
podman pod inspect my_pod

It is possible to create a pod automatically using the podman create or podman run commands to create a container. Using the --pod=new:{pod_name} flag creates a new pod with the specified name and associates the new container with it.

podman run -dit \
           --name={container_name} \
           --pod=new:{pod_name}
           ...

The pod takes on the characteristics of the container, so I don't like this option. It feels better to create the pod explicitly.

Create a Database Container

We create containers in the normal manner, but instead of using the "--network" flag, we use the "--pod" flag to indicate which pod the container should be created inside. We are going to use the default environment settings inside the container, including all the passwords. This would be silly for a real container, but for this example it keeps things simple. Notice the use of the "--volume" flag to specify the persistent storage.

podman run -dit \
           --name=ol8_19_con \
           --pod=my_pod \
           --volume=/u01/volumes/ol8_19_ords_db/:/u02 \
           ol8_19:latest

We can track the progress of the container start up using the following command.

podman logs --follow ol8_19_con

Create an ORDS Container

We create an ORDS container in a similar manner. We used the default environment settings for the database, so we can mostly use the default environment settings for the ORDS container, as the database port, service and passwords will be set to the same default values. We do need to tell the container where to find the database using the "-e" flag. For Docker we would specify the container name, but for Podman we just use localhost.

podman run -dit \
           --name ol8_ords_con \
           --pod=my_pod \
           -e="DB_HOSTNAME=localhost" \
           -v=/u01/volumes/ol8_19_ords_tomcat:/u01/config/instance1 \
           ol8_ords:latest

We can track the progress of the container start up using the following command.

podman logs --follow ol8_ords_con

Test It

Once both containers are running in the pod, we can access ORDS in the normal way and we'll be presented with the APEX login screen.

https://localhost:8443/ords/

Stopping/Starting the Containers

We can stop and start containers individually, or via the pod.

# Stop all containers in the pod.
podman pod stop my_pod

# Start all containers in the pod.
podman pod start my_pod


# Stop containers individually.
podman stop ol8_ords_con
podman stop ol8_19_con

# Start containers individually.
podman start ol8_ords_con
podman start ol8_19_con

Remove the Containers and Pod

The containers need to be stopped and removed before we can remove the pod. We stop all containers in the pod.

podman pod stop my_pod

Now we can remove the containers and remove the pod.

podman rm -vf ol8_ords_con
podman rm -vf ol8_19_con

podman pod rm my_pod

For more information see:

Hope this helps. Regards Tim...

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