Exercise: Containers review

Containers review

• Build a tagged image from a Containerfile.
• Run it as a Quadlet user service.
• Enable lingering and open the port for another host.

Before you start: reset the servers and complete this chapter's lessons. You work on servera as student, connected with ssh student@servera; lab start and lab grade run on workstation. The lab needs access to registry.access.redhat.com.

On servera, as student:

1. Install podman if needed. Create ~/portal/index.html with Portal is up and a Containerfile that builds on registry.access.redhat.com/ubi9/httpd-24 and copies the page.
2. Build it as localhost/portal:1.
3. Write ~/.config/containers/systemd/portal.container: that image, PublishPort=8080:8080, Restart=always, wanted by default.target.
4. Start portal.service; the container systemd-portal must run.
5. Enable lingering for student, open 8080/tcp permanently, and test from serverb.
6. On workstation, fill in answers.txt.

Start the exercise

[student@workstation ~]$ lab start sa-containers-review
[student@workstation ~]$ ssh student@servera
[student@servera ~]$

The image

[student@servera ~]$ sudo dnf install -y podman > /dev/null
[student@servera ~]$ mkdir -p ~/portal && cd ~/portal
[student@servera portal]$ echo "Portal is up" > index.html
[student@servera portal]$ cat > Containerfile <<'EOT'
FROM registry.access.redhat.com/ubi9/httpd-24:latest
COPY index.html /var/www/html/index.html
EOT
[student@servera portal]$ podman build -t localhost/portal:1 . | tail -2
Successfully tagged localhost/portal:1
8783f7652eb1f58df91e9c935a51986cbb9e3de30809eb517a08e5e4f883b136

The service

[student@servera portal]$ mkdir -p ~/.config/containers/systemd
[student@servera portal]$ cat > ~/.config/containers/systemd/portal.container <<'EOT'
[Unit]
Description=Portal container

[Container]
Image=localhost/portal:1
PublishPort=8080:8080

[Service]
Restart=always

[Install]
WantedBy=default.target
EOT
[student@servera portal]$ systemctl --user daemon-reload
[student@servera portal]$ systemctl --user start portal.service
[student@servera portal]$ sleep 3; systemctl --user is-active portal.service; curl -s localhost:8080
active
Portal is up

Boot and network

[student@servera portal]$ sudo loginctl enable-linger student
[student@servera portal]$ sudo firewall-cmd --permanent --add-port=8080/tcp; sudo firewall-cmd --reload
success
success
[student@serverb ~]$ curl -s -m 3 http://servera:8080/
Portal is up

A reboot of servera is the final proof: the portal answers again after a minute, with nobody logged in.

Grade

On workstation, fill in answers.txt and grade:

Check your work with lab grade sa-containers-review, then put the exercise away with lab finish sa-containers-review.