Ubuntu 20.04
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Docker : Use Dockerfile2020/06/02

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.
vi Dockerfile
# create new

FROM ubuntu
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

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

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

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

Sending build context to Docker daemon   25.6kB
Step 1/8 : FROM ubuntu
 ---> 7e0aa2d69a15
Step 2/8 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Using cache
 ---> a2fa80a6247c
Step 3/8 : RUN apt-get update
 ---> Using cache
 ---> 676629fe1237
Successfully built 84bcc150feb9
Successfully tagged srv.world/ubuntu-apache2:latest

docker images

REPOSITORY                 TAG       IMAGE ID       CREATED          SIZE
srv.world/ubuntu-apache2   latest    84bcc150feb9   3 minutes ago    216MB
srv.world/ubuntu-nginx     latest    8f1fbe417eb2   14 minutes ago   160MB
ubuntu                     latest    7e0aa2d69a15   2 weeks ago      72.7MB

# run container

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

docker ps

CONTAINER ID   IMAGE                      COMMAND                  CREATED         STATUS         PORTS                  NAMES
91f835c52b0f   srv.world/ubuntu-apache2   "/usr/sbin/apachectl…"   8 seconds ago   Up 7 seconds>80/tcp   ecstatic_pare

# verify accesses

curl localhost:8081

Dockerfile Test on Apache2
The format of Dockerfile is [INSTRUCTION arguments] .
Refer to the following description for INSTRUCTION.
FROM iIt sets the Base Image for subsequent instructions.
MAINTAINER It sets the Author field of the generated images.
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 remore 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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