rocky-linux · sspencerwire · Apr 19, 2024 · Apr 3, 2024 · Apr 3, 2024
diff --git a/docs/gemstones/containers/podman.md b/docs/gemstones/containers/podman.md
@@ -1,6 +1,6 @@
 ---
 title: Podman
-author: Neel Chauhan
+author: Neel Chauhan, Antoine Le Morvan
 contributors: Steven Spencer, Ganna Zhyrnova
 date: 2024-03-07
 tags:
@@ -10,21 +10,89 @@ tags:
 
 # Introduction
 
-[Podman](https://podman.io/) is a Docker-compatible alternative container runtime that, unlike Docker, is included in the Rocky Linux repositories and can run containers as a `systemd` service.
+[Podman](https://podman.io/) (Pod Manager) is a container and container image management tool compatible with the [OCI](https://opencontainers.org/) (Open Container Initiative).
+
+Podman:
+
+* works without daemon (it can run containers as a `systemd` service),
+* allows you to manage containers as an unprivileged user (no need to be root),
+* is included, unlike docker, in the Rocky Linux repositories.
+
+That makes Podman not only a docker-compatible alternative container runtime, but much more.
 
 ## Install Podman
 
 Use the `dnf` utility to install Podman:
 
-```
+```bash
 dnf install podman
 ```
 
+You can retrieve the list of available podman subcommands with the following command:
+```bash
+$ podman --help
+
+Manage pods, containers and images
+
+Usage:
+  podman [options] [command]
+
+Available Commands:
+  attach      Attach to a running container
+  auto-update Auto update containers according to their auto-update policy
+...
+```
+
+Here is a non-exhaustive list of the most commonly used subcommands:
+
+| Subcommand  | Description                                                     |
+| ----------- | --------------------------------------------------------------- |
+| `build`     | Build an image using instructions from Containerfiles           |
+| `commit`    | Create new image based on the changed container                 |
+| `container` | Manage containers                                               |
+| `cp`        | Copy files/folders between a container and the local filesystem |
+| `create`    | Create but do not start a container                             |
+| `exec`      | Run a process in a running container                            |
+| `image`     | Manage images                                                   |
+| `images`    | List images in local storage                                    |
+| `info`      | Display podman system information                               |
+| `init`      | Initialize one or more containers                               |
+| `inspect`   | Display the configuration of object denoted by ID               |
+| `kill`      | Kill one or more running containers with a specific signal      |
+| `login`     | Log in to a container registry                                  |
+| `logs`      | Fetch the logs of one or more containers                        |
+| `network`   | Manage networks                                                 |
+| `pause`     | Pause all the processes in one or more containers               |
+| `ps`        | List containers                                                 |
+| `pull`      | Pull an image from a registry                                   |
+| `push`      | Push an image to a specified destination                        |
+| `restart`   | Restart one or more containers                                  |
+| `rm`        | Remove one or more containers                                   |
+| `rmi`       | Remove one or more images from local storage                    |
+| `run`       | Run a command in a new container                                |
+| `start`     | Start one or more containers                                    |
+| `stats`     | Display a live stream of container resource usage statistics    |
+| `stop`      | Stop one or more containers                                     |
+| `system`    | Manage podman                                                   |
+| `top`       | Display the running processes of a container                    |
+| `unpause`   | Unpause the processes in one or more containers                 |
+| `volume`    | Manage volumes                                                  |
+
+!!! NOTE
+
+    Podman can execute almost any Docker commands thanks to its similar CLI interface.
+
+If you need to use a compose file, remember to install the ``podman-compose`` package :
+
+```bash
+dnf install podman-compose
+```
+
 ## Adding a container
 
 Let us run a [Nextcloud](https://nextcloud.com/) self-hosted cloud platform as an example:
 
-```
+```bash
 podman run -d -p 8080:80 nextcloud
 ```
 
@@ -62,3 +130,167 @@ systemctl enable nextcloud
 Replace `compassionate_meninsky` with your container's assigned name.
 
 When your system reboots, Nextcloud will restart in Podman.
+
+## DockerFiles
+
+A DockerFile is a file used by docker to create custom container images, and good news, as Podman is fully compatible with Dockerfile, you can then build your container images with Podman in the same way as you would with Docker.
+
+We will create an httpd server based on a RockyLinux 9.
+
+Create a folder dedicated to our image:
+
+```bash
+mkdir myrocky && cd myrocky
+```
+
+Create an `index.html` file that will be served by our webserver:
+
+```bash
+echo "Welcome to Rocky" > index.html
+```
+
+Then, create a `Dockerfile` file with the following content:
+
+```text
+# Use the latest rockylinux image as a start
+FROM rockylinux:9
+
+# Make it uptodate
+RUN dnf -y update
+# Install and enable httpd
+RUN dnf -y install httpd
+RUN systemctl enable httpd
+# Copy the local index.html file into our image
+COPY index.html /var/www/html/
+
+# Expose the port 80 to the outside
+EXPOSE 80
+
+# Start the services
+CMD [ "/sbin/init" ]
+```
+
+We are now ready to build our image called `myrockywebserver`:
+
+```bash
+$ podman build -t myrockywebserver .
+
+STEP 1/7: FROM rockylinux:9
+Resolved "rockylinux" as an alias (/etc/containers/registries.conf.d/000-shortnames.conf)
+Trying to pull docker.io/library/rockylinux:9...
+Getting image source signatures
+Copying blob 489e1be6ce56 skipped: already exists
+Copying config b72d2d9150 done
+Writing manifest to image destination
+STEP 2/7: RUN dnf -y update
+Rocky Linux 9 - BaseOS                          406 kB/s | 2.2 MB     00:05    
+Rocky Linux 9 - AppStream                       9.9 MB/s | 7.4 MB     00:00    
+Rocky Linux 9 - Extras                           35 kB/s |  14 kB     00:00    
+Dependencies resolved.
+================================================================================
+ Package                   Arch      Version                 Repository    Size
+================================================================================
+Upgrading:
+ basesystem                noarch    11-13.el9.0.1           baseos       6.4 k
+ binutils                  x86_64    2.35.2-42.el9_3.1       baseos       4.5 M
+...
+Complete!
+--> 2e8b93d30f31
+STEP 3/7: RUN dnf -y install httpd
+Last metadata expiration check: 0:00:34 ago on Wed Apr  3 07:29:56 2024.
+Dependencies resolved.
+================================================================================
+ Package                Arch       Version                  Repository     Size
+================================================================================
+Installing:
+ httpd                  x86_64     2.4.57-5.el9             appstream      46 k
+...
+Complete!
+--> 71db5cabef1e
+STEP 4/7: RUN systemctl enable httpd
+Created symlink /etc/systemd/system/multi-user.target.wants/httpd.service → /usr/lib/systemd/system/httpd.service.
+--> 423d45a3cb2d
+STEP 5/7: COPY index.html /var/www/html/
+--> dfaf9236ebae
+STEP 6/7: EXPOSE 80
+--> 439bc5aee524
+STEP 7/7: CMD [ "/sbin/init" ]
+COMMIT myrockywebserver
+--> 7fcf202d3c8d
+Successfully tagged localhost/myrockywebserver:latest
+7fcf202d3c8d059837cc4e7bc083a526966874f978cd4ab18690efb0f893d583
+```
+
+We can now launch our podman image and check if it was well started:
+
+```bash
+$ podman run -d --name rockywebserver -p 8080:80 localhost/myrockywebserver
+282c09eecf845c7d9390f6878f9340a802cc2e13d654da197d6c08111905f1bd
+
+$ podman ps
+CONTAINER ID  IMAGE                              COMMAND     CREATED         STATUS         PORTS                 NAMES
+282c09eecf84  localhost/myrockywebserver:latest  /sbin/init  16 seconds ago  Up 16 seconds  0.0.0.0:8080->80/tcp  rockywebserver
+```
+
+We launched our podman image in daemon mode (`-p`) and give it `rockywebserver` as a name (option `--name`).
+
+As we redirect the port 80 (protected) to the port 8080 with the `-p` option, let's check if we are listening on:
+
+```bash
+ss -tuna | grep "*:8080"
+tcp   LISTEN    0      4096                *:8080             *:*
+```
+
+We can now check if the index.html file is accessible:
+
+```bash
+$ curl http://localhost:8080
+Welcome to Rocky
+```
+
+Congrats! We can now stop and destroy our running image, giving its name we provided during its creation:
+
+```bash
+podman stop rockywebserver && podman rm rockywebserver
+```
+
+If you relaunch the build process, you can observe that `podman` will use a cache at each step of the build:
+
+```bash
+$ podman build -t myrockywebserver .
+
+STEP 1/7: FROM rockylinux:9
+STEP 2/7: RUN dnf -y update
+--> Using cache 2e8b93d30f3104d77827a888fdf1d6350d203af18e16ae528b9ca612b850f844
+--> 2e8b93d30f31
+STEP 3/7: RUN dnf -y install httpd
+--> Using cache 71db5cabef1e033c0d7416bc341848fbf4dfcfa25cd43758a8b264ac0cfcf461
+--> 71db5cabef1e
+STEP 4/7: RUN systemctl enable httpd
+--> Using cache 423d45a3cb2d9f5ef0af474e4f16721f4c84c1b80aa486925a3ae2b563ba3968
+--> 423d45a3cb2d
+STEP 5/7: COPY index.html /var/www/html/
+--> Using cache dfaf9236ebaecf835ecb9049c657723bd9ec37190679dd3532e7d75c0ca80331
+--> dfaf9236ebae
+STEP 6/7: EXPOSE 80
+--> Using cache 439bc5aee524338a416ae5080afbbea258a3c5e5cd910b2485559b4a908f81a3
+--> 439bc5aee524
+STEP 7/7: CMD [ "/sbin/init" ]
+--> Using cache 7fcf202d3c8d059837cc4e7bc083a526966874f978cd4ab18690efb0f893d583
+COMMIT myrockywebserver
+--> 7fcf202d3c8d
+Successfully tagged localhost/myrockywebserver:latest
+7fcf202d3c8d059837cc4e7bc083a526966874f978cd4ab18690efb0f893d583
+```
+
+Hopefully, you can clear that cache thanks to the `prune` subcommand:
+
+```bash
+podman system prune -a -f
+```
+
+| Options     | Description                                             |
+| ----------- | ------------------------------------------------------- |
+| `-a`        | Remove all unused data, not only the external to podman |
+| `-f`        | No prompt for confirmation                              |
+| `--volumes` | Prune volumes                                           |