Docker : Use Dockerfile2023/06/22

	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:~#

vi Dockerfile

# create new

FROM debian
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/debian-apache2:latest ./

Sending build context to Docker daemon  18.43kB
Step 1/8 : FROM debian
 ---> 49081a1edb0b
Step 2/8 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Running in 96b14acc8751
Removing intermediate container 96b14acc8751
 ---> 8c66e9445174
Step 3/8 : RUN apt-get update
 
.....
.....

Removing intermediate container 80ec238dedae
 ---> 431c51e7819a
Successfully built 431c51e7819a
Successfully tagged srv.world/debian-apache2:latest

root@dlp:~#

docker images

REPOSITORY                 TAG       IMAGE ID       CREATED              SIZE
srv.world/debian-apache2   latest    431c51e7819a   About a minute ago   252MB
srv.world/debian-nginx     latest    5a202ab0ab76   6 minutes ago        153MB
debian                     latest    49081a1edb0b   9 days ago           116MB

# run container

root@dlp:~#

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

bc96f9eae7cf186114e33599f1c95704b9545faa36d22ae4743864f97432014b

root@dlp:~#

docker ps

CONTAINER ID   IMAGE                      COMMAND                  CREATED          STATUS         PORTS                                   NAMES
bc96f9eae7cf   srv.world/debian-apache2   "/usr/sbin/apachectl…"   10 seconds ago   Up 9 seconds   0.0.0.0:8081->80/tcp, :::8081->80/tcp   hungry_mahavira

# 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.
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 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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