Ubuntu 19.04
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Docker : Use Dockerfile2019/04/25

Use Dockerfile and create Docker images automatically.
It is also useful for configuration management.
[1] For example, Create a Dockerfile to install apache2 and sshd and also install Supervisor to control multiple services on a Container.
vi Dockerfile
# create new

FROM ubuntu
MAINTAINER ServerWorld <admin@srv.world>

RUN apt-get update
RUN apt-get -y install openssh-server apache2 supervisor
RUN echo "Hello DockerFile World" > /var/www/html/index.html
RUN mkdir /var/run/sshd; chmod 755 /var/run/sshd
RUN mkdir /root/.ssh; chown root. /root/.ssh; chmod 700 /root/.ssh
RUN ssh-keygen -A

ADD supervisord.conf /etc/supervisor/supervisord.conf
ADD .ssh/id_rsa.pub /root/.ssh/authorized_keys

EXPOSE 22 80
CMD ["/usr/bin/supervisord"]

# create a Supervisor template

vi supervisord.conf

command=/usr/sbin/sshd -D

command=/usr/sbin/apachectl -D FOREGROUND

# generate SSH key

ssh-keygen -q -N "" -f /root/.ssh/id_rsa
# build image ⇒ docker build -t [image name]:[tag] ./

docker build -t web_server:latest ./

Sending build context to Docker daemon  22.02kB
Step 1/12 : FROM ubuntu
 ---> 94e814e2efa8
Step 2/12 : MAINTAINER ServerWorld <admin@srv.world>
 ---> Running in ebfa177f67cf
Removing intermediate container ebfa177f67cf
 ---> 24ed6b8249be
Step 3/12 : RUN apt-get update
 ---> Running in 0a9fb4a2bc6e
Successfully built 11c1025998ec
Successfully tagged web_server:latest

docker images

REPOSITORY                 TAG                 IMAGE ID            CREATED              SIZE
web_server                 latest              11c1025998ec        About a minute ago   306MB
srv.world/ubuntu_apache2   latest              c0d10606acde        6 minutes ago        210MB
ubuntu                     latest              94e814e2efa8        6 weeks ago          88.9MB

# run Container on background

docker run -d -p 2022:22 -p 8081:80 web_server

docker ps

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                                        NAMES
00af9375a7f2        web_server          "/usr/bin/supervisord"   19 seconds ago      Up 18 seconds>22/tcp,>80/tcp   zealous_williamson

# verify accesses

curl localhost:8081

Hello DockerFile World
ssh -p 2022 localhost /bin/hostname

The authenticity of host '[localhost]:2022 ([::1]:2022)' can't be established.
ECDSA key fingerprint is SHA256:7hL139J8xbG3RwgHqYLCw3S+0QzPRSbQzq+r+zO9yag.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[localhost]:2022' (ECDSA) to the list of known hosts.
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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