Ubuntu 22.04
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Docker : Use Dockerfile
2022/09/08
 
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:~#
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

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 ./

Sending build context to Docker daemon  27.14kB
Step 1/8 : FROM ubuntu
 ---> 2dc39ba059dc
Step 2/8 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Running in de1d1b875fe0
Removing intermediate container de1d1b875fe0
 ---> e25181251546
Step 3/8 : RUN apt-get update
 ---> Running in 836063f687fc
 
.....
.....

Step 8/8 : CMD ["/usr/sbin/apachectl", "-D", "FOREGROUND"]
 ---> Running in 31d5749415a9
Removing intermediate container 31d5749415a9
 ---> b7891f747bd5
Successfully built b7891f747bd5
Successfully tagged srv.world/ubuntu-apache2:latest

root@dlp:~#
docker images

REPOSITORY                 TAG       IMAGE ID       CREATED              SIZE
srv.world/ubuntu-apache2   latest    b7891f747bd5   About a minute ago   227MB
srv.world/ubuntu-nginx     latest    51f5190bb9d9   6 minutes ago        170MB
ubuntu                     latest    2dc39ba059dc   5 days ago           77.8MB

# run container

root@dlp:~#
docker run -d -p 8081:80 srv.world/ubuntu-apache2

60784c2019f6fc53169367c51b4aaf75ed7fae1cdbf107bbccd95bc40c29719f
root@dlp:~#
docker ps

CONTAINER ID   IMAGE                      COMMAND                  CREATED         STATUS         PORTS                                   NAMES
60784c2019f6   srv.world/ubuntu-apache2   "/usr/sbin/apachectl…"   8 seconds ago   Up 8 seconds   0.0.0.0:8081->80/tcp, :::8081->80/tcp   nifty_pascal

# 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 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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