Docker : Use Dockerfile2026/05/08

	Use Dockerfile and create Docker images automatically. It is also useful for configuration management.
[1]	For example, Create a Dockerfile that Apache2 is installed and started.

root@dlp:~#

apt -y install docker-buildx

root@dlp:~#

vi Dockerfile

# create new

FROM ubuntu
LABEL Maintainer="ServerWorld <admin@srv.world>"

RUN apt-get update
RUN apt-get -y install tzdata
RUN apt-get -y install apache2
RUN echo "Dockerfile Test on Apache2" > /var/www/html/index.html

EXPOSE 80
CMD ["/usr/sbin/apachectl", "-D", "FOREGROUND"]

# build image ⇒ docker build -t [image name]:[tag] .

root@dlp:~#

docker build -t srv.world/ubuntu-apache2:latest ./

[+] Building 1.1s (9/9) FINISHED                                                                                 docker:default
 => [internal] load build definition from Dockerfile                                                                       0.0s
 => => transferring dockerfile: 305B                                                                                       0.0s
 => [internal] load metadata for docker.io/library/ubuntu:latest                                                           0.0s
 => [internal] load .dockerignore                                                                                          0.0s
 => => transferring context: 2B                                                                                            0.0s
 => [1/5] FROM docker.io/library/ubuntu:latest@sha256:f3d28607ddd78734bb7f71f117f3c6706c666b8b76cbff7c9ff6e5718d46ff64     0.0s
 => => resolve docker.io/library/ubuntu:latest@sha256:f3d28607ddd78734bb7f71f117f3c6706c666b8b76cbff7c9ff6e5718d46ff64     0.0s
 => CACHED [2/5] RUN apt-get update                                                                                        0.0s
 => CACHED [3/5] RUN apt-get -y install tzdata                                                                             0.0s
 => CACHED [4/5] RUN apt-get -y install apache2                                                                            0.0s
 => CACHED [5/5] RUN echo "Dockerfile Test on Apache2" > /var/www/html/index.html                                          0.0s
 => exporting to image                                                                                                     1.0s
 => => exporting layers                                                                                                    0.0s
 => => exporting manifest sha256:df9756eaa0adea8deb22be4b35b58b1551ff9ef552f22321f66b715cc448ee74                          0.0s
 => => exporting config sha256:d7556517944c60c9f20e5c39f9a08720d9f4f9ba2d3ea280b1e22f84b5b09231                            0.0s
 => => exporting attestation manifest sha256:d128efc958573f831fa519ca3c1dc265d676c987f9a23e4eff6520a8f237efb0              0.0s
 => => exporting manifest list sha256:c6da801438b04c9cc6ce186061601eb255c38317ae2018e0e33575e8b3503f91                     0.0s
 => => naming to srv.world/ubuntu-apache2:latest                                                                           0.0s
 => => unpacking to srv.world/ubuntu-apache2:latest

root@dlp:~#

docker images

IMAGE                             ID             DISK USAGE   CONTENT SIZE   EXTRA
srv.world/ubuntu-apache2:latest   c6da801438b0        340MB         92.8MB
srv.world/ubuntu-nginx:latest     305dfeaadebc        227MB         69.9MB    U
ubuntu:latest                     f3d28607ddd7        160MB         45.3MB    U

# run container

root@dlp:~#

docker run -d -p 8081:80 srv.world/ubuntu-apache2

735e80df684c837affaefe93fc5e56e0813239969092c0dfe9859eb11f74e0eb

root@dlp:~#

docker ps

CONTAINER ID   IMAGE                      COMMAND                  CREATED          STATUS          PORTS                                     NAMES
735e80df684c   srv.world/ubuntu-apache2   "/usr/sbin/apachectl…"   16 seconds ago   Up 15 seconds   0.0.0.0:8081->80/tcp, [::]:8081->80/tcp   condescending_boyd

# verify accesses

root@dlp:~#

curl localhost:8081

Dockerfile Test on Apache2

The format of Dockerfile is [INSTRUCTION arguments] .
Refer to the following description for INSTRUCTION.

INSTRUCTION	Description
FROM	It sets the Base Image for subsequent instructions.
RUN	It will execute any commands when Docker image will be created.
CMD	It will execute any commands when Docker container will be executed.
ENTRYPOINT	It will execute any commands when Docker container will be executed.
LABEL	It adds metadata to an image.
EXPOSE	It informs Docker that the container will listen on the specified network ports at runtime.
ENV	It sets the environment variable.
ADD	It copies new files, directories or remote file URLs.
COPY	It copies new files or directories. The differences of [ADD] are that it's impossible to specify remote URL and also it will not extract archive files automatically.
VOLUME	It creates a mount point with the specified name and marks it as holding externally mounted volumes from native host or other containers.
USER	It sets the user name or UID.
WORKDIR	It sets the working directory.

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