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Lab 1: Podman Introduction

Prerequisites

Make sure to register for a free account at Docker Hub.

Setting Up Podman

Follow installation instructions for podman.

Working with podman - "Hello World" using Tomcat

In this section we will walk through finding an image, pulling it to the local environment, instantiating a container from the image, stopping the container and removing the stopped container.

Launch a shell and confirm that podman is installed. The version number isn't particular important.

$ podman -v
podman version 3.4.4

Search for tomcat

$ podman search tomcat

Pull tomcat image

$ podman pull docker.io/library/tomcat

Validate the pull of the tomcat image

$ podman images

REPOSITORY                TAG     IMAGE ID      CREATED     SIZE
docker.io/library/tomcat  latest  08efef7ca980  2 days ago  679 MB

Create a container based on the image, we use the following parameters:

  • -d runs the container in detached mode returning only the container ID
  • -p : binds the host port to the exposed container port
  • --name is used to provide a container name
  • remember all these options have to be before the image definition
$ podman run -d --name tomcat-1 -p 8080:8080 tomcat

Find the container instance

$ podman ps

Stop the container instance and delete the stopped instance.

$ podman stop tomcat-1
$ podman rm tomcat-1

Working with podman - Leveraging CouchDB

After running a Tomcat instance we will work with a CouchDB image leveraging similar options

  • -e allows to set environment variables
  • imagename:TAG allows to specify a certain image tag to pull from the repository
$ podman run -d -p 5984:5984 --name couchdb-1 -e COUCHDB_USER=admin -e COUCHDB_PASSWORD=password apache/couchdb:latest

Unable to find image 'apache/couchdb:latest' locally
latest: Pulling from apache/couchdb
d121f8d1c412: Pull complete
77bb2d366040: Pull complete
93df8fed85d6: Pull complete
Digest: sha256:95bb69dd700df71578ac1b4011f40ca66369e6d132b80f1520a3d21e7bff084f
Status: Downloaded newer image for apache/couchdb:latest
4de83b227b03bf17a42a1915d87928e310c44764ef9776083963276eb114e908

The output above was captured while the image was still downloading from docker-hub. When the download is done you don't see anything from the container. Instead you see a long hex id like 4de83b227b03bf17a42a1915d87928e310c44764ef9776083963276eb114e908. This is the id of the container.

Here is how you would see the running container. Notice only the first part of that long hex id is displayed. Typically this is more than enough to uniquely identify that container. podman ps provides information about when the container was created, how long it has been running, the name of the image, as well as the name of the container. Note that each container must have a unique name. You can specify a name for each container as long it is unique.

$ podman ps
CONTAINER ID   IMAGE                            COMMAND        CREATED        STATUS       PORTS                   NAMES
4de83b227b03   docker.io/apache/couchdb:latest  /opt/couchdb   4 minutes ago  Up 4 minutes 0.0.0.0:5984->5984/tcp  couchdb-1

To validate CouchDB is up an running execute a curl command against the exposed port. You should receive a JSON-based welcome message.

$ curl localhost:5984
{"couchdb":"Welcome","version":"3.1.1","git_sha":"ce596c65d","uuid":"509813e7f91cb260fb30039f7421abab","features":["access-ready","partitioned","pluggable-storage-engines","reshard","scheduler"],"vendor":{"name":"The Apache Software Foundation"}}

Create a new customer database with the following curl command.

$ curl -X PUT http://admin:password@localhost:5984/customer
{"ok":true}

Insert a customer entry to the database leveraging the following HTTP PUT request.

$ curl -X PUT http://admin:password@localhost:5984/customer/1 -d '{"firstName": "Hugo", "lastName": "Boss"}'
{"ok":true,"id":"1","rev":"1-b8745a7b645d3f29f0b19274bf63707b"}

To finalize our tests we will retrieve the created document from the customer database.

$ curl -X GET http://admin:password@localhost:5984/customer/1
{"_id":"1","_rev":"1-b8745a7b645d3f29f0b19274bf63707b","firstName":"Hugo","lastName":"Boss"}

Now let's clean up the environment. Begin with stopping the container leveraging the given name.

$ podman stop couchdb-1
4de83b227b03

Notice the image still exists. Go ahead and try to delete the CouchDB image with podman rmi apache/couchdb

$ podman rmi apache/couchdb
rror: 1 error occurred:
        * could not remove image 1916ea74a583b0e0df17b2d14418095ce7a614027cb363d014f2b8af584ebcf2 as it is being used by 1 containers: image is being use

Oops, we can't delete the image until we remove the couchdb container. Note that podman ps -a will show us all the containers, not just the ones that are running.

$ docker ps -a
4de83b227b03   docker.io/apache/couchdb:latest  /opt/couchdb/bin/... 17 minutes ago   Exited (0) 4 minutes ago   couchdb-1

With podman rm <container name|id> you can remove a container. Delete the couchdb container, delete the couchdb image and make sure it's gone.

$ podman rm couchdb-1

$ podman rmi apache/couchdb
Untagged: apache/couchdb:latest
Untagged: apache/couchdb@sha256:95bb69dd700df71578ac1b4011f40ca66369e6d132b80f1520a3d21e7bff084f
Deleted: sha256:1916ea74a583b0e0df17b2d14418095ce7a614027cb363d014f2b8af584ebcf2
Deleted: sha256:9894abfedce3d1ad1832f96f48c62b1e2c5e7f0e7e79d5b35e3d766df588221c
Deleted: sha256:79de819838b0479a03a484cff2f8df9e64207de6f1f0303c508b3627c64754bc
Deleted: sha256:618ec9e04da8fe87c14a90caacf957f9308124e219604fc3d5b60a6e4ba52df8
Deleted: sha256:e8c96b7c719eb50273cd44b25aaf5b108e5334088912e749f88ad1356c32cb04
Deleted: sha256:19760c4688fcb49f88e75d80de15dc559cad3eb014bbc3d6f42140ae7beac721
Deleted: sha256:e6fa3b97bbfb030a9f33b6c8a96034ef1e58a5559490fbe87e7b4124ddaf15e0

$ podman images
REPOSITORY                   TAG                 IMAGE ID            CREATED             SIZE
docker.io/library/tomcat     latest              08efef7ca980        2 days ago          679 MB

Congratulations, you have done your first steps with Podman.

Optional Lab 1

If you want to build your own image you can checkout the /node_docker folder in this repository and build + test your own based on a simple Node.JS sample (look into the README for some hints).