Podman: Getting Started
Your getting started guide to kickstart the Podman journey
This post is based on the video I made in TechPrimers. If you like the video format, the link for the video is here
What is Podman? How is it different from Docker?
Podman is a Daemonless Container Engine which can run OCI compatible images. It can run only on Linux machines (for now). If you have either Windows or OSX, you will have to use a Virtual Linux VM in VM Box or Hyperkit.
The major differences between Docker and podman (Pod Manager Tool) are —
- Daemoneless — This feature differentiates itself from Docker, which runs a docker daemon to execute tasks. Podman is light-weight and doesn’t require an always running instance for running containers.
- Rootless — Podman can be run as either root or non-root. We can run podman containers as non-root user and still be compliant with running containers.
- Pods — The term Pods originated from Kubernetes. Pods are a collections of containers which are run as close as possible. Podman provides this feature out of the box for running multiple containers together.
Install Podman in Linux
Based on your runtime, you can choose the steps for Podman installation from the official documentation here. I will be using an Amazon EC2 with Linux, hence i will be using the following commands:
sudo curl -L -o /etc/yum.repos.d/devel:kubic:libcontainers:stable.repo https://download.opensuse.org/repositories/devel:/kubic:/libcontainers:/stable/CentOS_7/devel:kubic:libcontainers:stable.repo
sudo yum -y install yum-plugin-copr
sudo yum -y copr enable lsm5/container-selinux
sudo yum -y install podmanTo verify if podman is installed successfully, we can check the version of the podman cli. In this case, I’m using 1.9.3 version of podman cli.
podman versionVersion: 1.9.3
RemoteAPI Version: 1
Go Version: go1.13.4
OS/Arch: linux/amd64
If you are familiar with docker, all the commands work on the same format with podman. There is a getting-started page in the podman site as well.
Some of the most commonly used commands are listed below
podman ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMESpodman images
REPOSITORY TAG IMAGE ID CREATED SIZE
How to run Docker images with Podman?
In order to run containers, I will be using an existing Docker image which I built using Docker sometime ago. The image is present in Github Package Registry (docker.pkg.github.com) here.
To pull the image from Github Package Registry, we need to connect the podman cli with the registry
podman login docker.pkg.github.com -u MovingToWeb
Password:
Login Succeeded!Once the login is successful, I’m going to pull the image which we require using the podman pull command
podman pull docker.pkg.github.com/techprimers/container-images/containers-demo:v2Trying to pull docker.pkg.github.com/techprimers/container-images/containers-demo:v2...
Getting image source signatures
Copying blob f910a506b6cb done
Copying blob c2274a1a0e27 [==================================] 67.5MiB / 67.5MiB
Copying blob f1e7efdf3e83 done
Copying blob e7c96db7181b done
Copying config d0871171aa done
Writing manifest to image destination
Storing signatures
d0871171aaf802ebb4a80c6f2ec9ea6de95f957529bc89e1bae7d294a83e64a5Summary
podman images shows the downloaded images in the local cache
podman imagesREPOSITORY TAG IMAGE ID CREATED SIZE
docker.pkg.github.com/techprimers/container-images/containers-demo v2 d0871171aaf8 11 months ago 125 MB
This image contains a Spring Boot package with actuators enabled in it. We can run this image as a daemon container using the below podman command
podman run -dt -p 8080:8080 containers-demo:v2
2270e63621e8b7f6db6f17c9eb3c8bfe4270ff208d95462139651b6c2532a56cpodman ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
2270e63621e8 docker.pkg.github.com/techprimers/container-images/containers-demo:v2 11 seconds ago Up 10 seconds ago 0.0.0.0:8080->8080/tcp mystifying_edison
This command starts a new container and maps the port 8080 from local VM to the 8080 from the container since the spring boot app is running on 8080.
To check the logs, podman logs <CONTAINER_ID> the command will help us
podman logs 2270e63621e8. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.2.0.RELEASE)2020-09-25 12:21:21.257 INFO 1 --- [ main] c.t.c.ContainersDemoApplication : Starting ContainersDemoApplication v0.0.1-SNAPSHOT on 2270e63621e8 with PID 1 (/containers-demo.jar started by root in /)
2020-09-25 12:21:21.261 INFO 1 --- [ main] c.t.c.ContainersDemoApplication : No active profile set, falling back to default profiles: default
2020-09-25 12:21:24.712 INFO 1 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)
2020-09-25 12:21:24.753 INFO 1 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2020-09-25 12:21:24.753 INFO 1 --- [ main] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.27]
2020-09-25 12:21:24.937 INFO 1 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2020-09-25 12:21:24.937 INFO 1 --- [ main] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 3533 ms
2020-09-25 12:21:26.925 INFO 1 --- [ main] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2020-09-25 12:21:27.474 INFO 1 --- [ main] o.s.b.a.e.web.EndpointLinksResolver : Exposing 2 endpoint(s) beneath base path '/actuator'
2020-09-25 12:21:27.625 INFO 1 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2020-09-25 12:21:27.628 INFO 1 --- [ main] c.t.c.ContainersDemoApplication : Started ContainersDemoApplication in 7.456 seconds (JVM running for 8.582)
Now that the application is UP and running, let’s to access the container’s actuator endpoint, we can use curl to verify the status of the application
curl http://localhost:8080/actuator/health
{"status":"UP"}I have not covered the build part using Podman. Do try building images from a Dockerfile. They should be seamless to run with Docker since podman also follows OCI compatible image format.
Summary
In short, Podman wraps up the features of Docker for providing a light-weight container runtime which can be run as Daemonless and Rootless mode.
Let’s Podman!
