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Inhaltsverzeichnis

erstes Docker Image selbst bauen
- Pakete
- Image bauen
  - testen
Dockerfile - Docker Images weiterbauen
Docker Image aktualisieren

erstes Docker Image selbst bauen

Pakete

Rocky Linux (10):

dnf config-manager --enable crb
dnf install -y epel-release
dnf install -y debootstrap

Debian (ab 12)

apt install -y debootstrap

Image bauen

¹⁾

sudo debootstrap --variant=minbase trixie ./debian http://debian/debian
sudo tar cC debian/ . | docker image import - ingo/debian:trixie

Tag latest hinzufügen:

docker image ls ingo/debian:trixie

→ id rauskopieren (z.B. dc9f1edde160)

docker image tag dc9f1edde160 ingo/debian:latest

testen

docker container run ingo/debian echo hello world

→ hello world

Dockerfile - Docker Images weiterbauen

mkdir nginx
cd nginx

Dockerfile

FROM ingo/debian:trixie
 
ENV DEBIAN_FRONTEND=noninteractive
RUN set -eux; \
  apt-get -qq update; \
  apt-get install -y --no-install-recommends nginx
RUN echo 'A warm welcome from your Dockerfile' > /var/www/html/index.html
EXPOSE 80
ENTRYPOINT ["/usr/sbin/nginx", "-g", "daemon off;"]
 
ARG REFRESHED_AT=2026-01-07
LABEL version="0.0.1"
LABEL maintainer="me@example.com"
LABEL org.opencontainers.image.authors="me@example.com"
LABEL org.opencontainers.image.created=$REFRESHED_AT

²⁾

podman

ENTRYPOINT / CMD / run-Command

`ENTRYPOINT`	`CMD`	run-Command	ausgeführt wird
["script.sh"]			script.sh
["script.sh"]		/bin/dash	script.sh /bin/dash
["script.sh"]	["httpd"]		script.sh httpd
["script.sh"]	["httpd"]	/bin/dash	script.sh /bin/dash
	["/bin/sh"]		/bin/sh
	["/bin/sh"]	/bin/dash	/bin/dash
			/bin/bash ³⁾

Image mit den Erweiterungen aus dem Dockerfile bauen:

docker build -t='ingo/nginx:0.0.1' .

Image anzeigen:

docker image ls ingo/nginx:0.0.1

→ id rauskopieren (z.B. 5879d7773761) Image taggen:

docker image tag 5879d7773761 ingo/nginx:latest

Container starten:

docker container run -d -p 80:80 --name my_nginx ingo/nginx

Zugriff auf nginx testen:

curl -s http://localhost:80

→ im Browser http://localhost öffnen

Docker Image aktualisieren

Dockerfile

…
RUN ln -sf /dev/stdout /var/log/nginx/access.log \
    && ln -sf /dev/stderr /var/log/nginx/error.log
…

docker build --no-cache --pull -t='ingo/nginx:0.0.2' .

podman

podman build --no-cache -t='ingo/nginx:0.0.2' .

→ allerdings werden dann alle 12 STEPs neu gebaut.

TODO: liegt das an dem fehlenden –pull? AI Slop Vermutung: Docker built your image without errors because it keeps un-namespaced local images as-is. In contrast, Podman automatically prefixes locally built or untagged registry images with localhost/ to prevent collisions with official registries. When you use the –pull flag, Podman is forced to try downloading a fresh version of that base image from an external source. Because it sees localhost/ingo/debian:trixie, Podman literally looks for a web-facing registry running on your actual machine (https://localhost/v2/). Since you don't have a container registry service actively running on port 443 of your host machine, the network request fails with „connection refused“

Unter Debian mit Docker version 26.1.5+dfsg1, build a72d7cd klappt –pull auch nicht. ERROR: failed to solve: ingo/debian:trixie: failed to resolve source metadata for docker.io/ingo/debian:trixie: pull access denied, repository does not exist or may require authorization: server message: insufficient_scope: authorization failed

Jetzt noch mal Container starten und

docker logs

ansehen.

Bauen mit einem Release Zeitstempel:

REFRESHED_AT=$(date '+%Y-%m-%d')
docker build --no-cache --pull \
  --build-arg REFRESHED_AT=$REFRESHED_AT \
  -t='ingo/nginx:0.0.2' \
  -t=ingo/nginx:$REFRESHED_AT .

¹⁾

anders als das Image aus https://hub.docker.com/_/debian ist dieses Image nicht reproduzierbar

²⁾

https://docs.docker.com/reference/dockerfile/

³⁾

https://docs.docker.com/reference/dockerfile/#understand-how-cmd-and-entrypoint-interact sagt error, not allowed. Docker Version 20.10.24+dfsg1 hat bash ausgeführt.