Docker and Podman are both tools that allow developers to package applications and their dependencies into isolated environments called containers. These containers are portable and can be deployed easily on any system, making them a popular choice for modern software development.
In this cheatsheet, we will cover the basics of Docker and Podman, including how to build, run, and manage containers, as well as how to work with volumes to persist data. You can use the same commands both for Podman and Docker.
Docker Installation
Install Docker on Linux
curl -sSL https://get.docker.com/ | sh
Start Docker
service start docker
Stop Docker
service stop docker
Docker Lifecycle
Pull (Download) Docker Image fedora
docker pull fedora
Search image fedora
docker search fedora
Run Image Fedora and assign the name “myfedora”
docker run --name myfedora fedora
Run image and removes container when stopped
docker run --rm fedora
Tag the image simple-server as simple-server:0.1
docker image tag simple-server simple-server:0.1
Run a shell on the Container myfedora:
docker exec -it myfedora /bin/bash
Runs a shell on the latest container started:
docker exec -it $(docker ps -q) bash
Build an image on the current directory from a Dockerfile
docker build .
Delete an image
docker rmi <myimage>
Attach to a running Container
docker attach <container>
See the logs of a Container
docker logs <container>
List active containers
docker ps -l
List active running Images
docker ps --format '{{.Image}}'
List available images
docker images
How to fetch only one attribute (f.e. Repository) from the Image List:
docker image ls --format "{{.Repository}}"
How to check all the layers (and their size) of an image
docker image tree my-image
How to stop all containers
docker stop $(docker ps -a -q)
Volumes
Creates a named Volume
docker volume create postgres-vol
How to import a Tar file into a volume (postgres-vol)
podman volume import postgres-vol ~/files/postgres-vol.tar.gz
How to delete a volume
docker volume rm postgres-vol
Start a container mounting a host directory (/home/jboss/deployments) as a volume in the WildFly container
docker run --rm --name wildfly --volume /home/jboss/deployments:/opt/jboss/wildfly/standalone/deployments:Z quay.io/wildfly/wildfly
Start a container mounting a Host directory as named volume in the PostgreSQL Container
docker run --name persisting-db -d --volume postgres-vol:/var/lib/pgsql/data postgresql-13
Ports and IPs
How to collect Socket Statistics from a Container
# First get the Container process ID (PID) for the Container myfedora
podman inspect myfedora --format '{{.State.Pid}}'
# Run the the nsenter command against the PID
sudo nsenter -t PID -n ss -pant
How to map an Host port (8080) with a Container port (8001):
podman run -d -p 8080:8001 --name http-server simple-server
Check mapped ports for the container “http-server”
docker port http-server
Get the IP Address of the last Container started:
docker inspect --format '{{ .NetworkSettings.IPAddress }}' $(docker ps -q)
Check any container’s IP Address:
docker inspect -f '{{ .NetworkSettings.IPAddress }}' http-server
Link Containers
Step 1: Start first CONTAINER
docker run --name CONTAINER
Step 2: Start LINKED container
docker run -d --link CONTAINER:ALIAS --name LINKED <myimag>
Cleanup
Kill running containers
docker kill $(docker ps -q)
Delete old containers
docker ps -a | grep 'weeks ago' | awk '{print $1}' | xargs -r docker rm
Delete stopped containers
docker rm -v `docker ps -a -q -f status=exited`
Delete dangling images
docker rmi $(docker images -q -f dangling=true)
Delete all images
docker rmi $(docker images -q)
Conclusion
In this cheatasheet, we’ve covered some of the most important Docker commands and options, including building images, running containers, managing volumes and networks, and doing regular maintenance of your images.
