10 Manage Containers

10.1 Manage and configure containers

podman is a project in replacement ot docker

$ sudo dnf install docker

it installs podman-docker(fake docker )

You can edit registries.conf file to make podman point to docker registres
$ vim /etc/containers/registries.conf

comment the unqualified-search-registries, create a new line with the new
unqualified-search-registries = ["docker.io"]

To emulated docker cli using podman :
$ sudo touch /etc/containers/nodocker

To search
$ docker search nginx

To pull an image
$ docker pull docker.io/library/nginx
$ docker pull nginx:1.20.2

To view images on a system
$ docker images

To delete an image, use the image id or image name 
$ docker rmi nginx:1.20.2

To run an image to a container
$ docker run nginx:1.20.2 

docker run, creates a new container, docker start, starts an old container that was stopped

To run a docker container in detached mode
$ docker run -d nginx

To explore running containers
$ docker ps
or
$ docker container list

To stop a container, you can user the name or id
$ docker stop <container_id>

To view all(active and stoppped) containers
$ docker ps --all
or
$ docker ps -a

To delete a container (must be stopped first)
$ docker rm <container_name>

NB: You can not delete an image that is used by container
You can force, it will stop and delete the container
$ docker rmi -force nginx

You can force and delete a container
$ docker rm --force <container-name>

You can name a container 
$ docker run -d -p 8080:80 --name mywebserver nginx

port-mapping : 8080 on host : 80 on container



10.2  Perform container management using commands such as podman and skopeo

Installing skopeo
$ sudo yum install skopeo


Inspecting Repositories
$ skopeo inspect docker://registry.fedoraproject.org/fedora:latest

Inspect containers
$ skopeo inspect --config docker://registry.fedoraproject.org/fedora:latest | jq

Copying Images
$ skopeo copy docker://quay.io/buildah/stable docker://registry.kodekloud.com/buildah

$ skopeo copy oci:busybox_ocilayout:latest dir:myemptydirectory

Deleting images
$ skopeo delete docker://localhost:5000/imagename:latest

syncing Registries
$ sudo skopeo sync --src docker --dest dir registry.fedoraproject.org/fedora:latest /home/bob/fedora



10.3 Configure a container to start automatically as a systemd service and attach persistent storage


To swith module streams
$ sudo yum module reset container-tools

$ sudo yum module install container-tools:3.0


Create a directory for service definition
$ mkdir -p ~/.config/systemd/user

Create a directory for persistent storage
$ mkdir ~/container_storage

Populate the storage directory with some content
$ echo "KodeKloud" > ~/container_storage/kodekloud.html

Create a container to generate unit files
$ podman run -d --name container_service -p 1025:8080 -v ~/container_storage:/var/www/html:Z registry.access.redhat.com+rhscl/httpd-24-rhel7

Test container
$ curl 127.0.0.1:1025/kodekloud.html

Create the systemd unit file
$ cd ~/.config/systemd/user

$ podman generate systemd --name container_service --files --new 
This command will generate a service file container-(name).service

Kill and remove the currently running container
$ podman kill container_service
and
$ podman rm container_service

Enable a loggin setting for the user
$ loginctl enable-linger
$ systemctl --user daemon-reload
$ systemctl --user enable --now container-(name).service

-- PRACTICE

loginctl enable-linger bob
export XDG_RUNTIME_DIR=/run/user/$(id -u)
systemctl --user daemon-reload
systemctl --user enable container-kodekloud.service --now