# Containers Containers allows developers to test and build applications on any computer by putting it in a container bundled with software code, libraries, and config files Docker
- software used to create and manage containers - can be installed on Linux - daemon can be controlled natively - not supported in RHEL 8
Podman
- developed by Red Hat 2018 as an alternative to docker - daemon less, open source, linux native tool to develop, manage and run containers
Red Hat provides a set of CLI tools
- podman - directly managing pods and container images (run, stop, start, ps attach, etc) - buildah - for building, pushing, and signing container images - skopeo - copying, inspecting, deleting, signing images - runc - providing container run and build features to podman and buildah - crun - optional runtime that can be configured and give greater flexibility, control & security for rootless containers
- images - containers can be created through images and containers can be converted to images - pods - groups of containers deployed together on the host
Basic Commands
dnf install podman -y install podman
alias docker=podman used when switching from docker to podman
podman -v check podman version
podman info check podman environment (see registries) if loading an image, looks locally, then to registries by order listed
Image --> Run Container --> Remove it
podman search httpd search container registries for an image
podman pull docker.io/library/httpd download image from a registry
podman images list downloaded images
podman run -d --name web1 -p 8080:80 docker.io/library/httpd create & start a container from an image
podman ps list running containers
curl localhost:8080 (or web) [http://localhost:8080](http://localhost:8080) verify application is accessible
podman stop web1 stop a container gracefully
podman rm -f web1 remove a container
Image --> Create Container --> Start Container
podman pull docker.io/library/httpd download image from a registry
podman create --name web2 -p 8081:80 docker.io/library/httpd create a container
podman ps -a verify status is created -a all containers
podman start web2 start an existing container
podman ps verify container status is running
curl localhost:8081 (or web) [http://localhost:8081](http://localhost:8081) verify application is accessible
podman logs web2 view output generated by container
Quadlet (Modern RHEL10) systemd container management
mkdir -p /etc/containers/systemd create directory for quadlet definitions
nano /etc/containers/systemd/web3.container … \[Unit\] Description=Apache Web Container \[Container\] Image=docker.io/library/httpd ContainerName=web3 PublishPort=8082:80 \[Service\] Restart=always \[Install\] WantedBy=multi-user.target create quadlet container definition file define systemd metadata description define container-specific settings specifies container image assigns name maps host port to container port defines systemd behaviour automatically restart container if it stops definte boot settings allow service to start automatically during boot
systemctl daemon-reload reload systemd configuration
systemctl enable --now web3.service enable service at boot and start now
systemctl status web3.service verify service status
podman ps verify container status is running
curl localhost:8082 (or web) [http://localhost:8082](http://localhost:8082) verify application is accessible